anatomy test 5

sensory pt 1

Hello Students. In this chapter we're going to talk about the census. So we'll first talk about generalized census, and then we'll get into more specific special senses that are innervated by cranial nerves. And as we highlight, each of these will highlight their morphology and how they can sense different types of stimuli. All right, let's get started. Lifted. So this PowerPoint we're going to talk about, we're going to break this up into two main categories. We're going to look at general food and we're going to look at special something. So within general fences we have, these are, these are receptors found throughout the body. So the things such as temperature, pain, touch, pressure, vibration, and proprioception. When we mean pain, there's a whole variety of ways to affect pain. This could be felt that are light things though that are undergoing extreme pressure. And it can also be anything the damaging sell, deliver all. Also associated with, within the general senses we have certain and terror receptors for that thing. Different levels of certain chemicals. So say measuring or sensing pH levels were fed thing a dissolved oxygen levels. So these general fences are usually interpreted by the spinal cord. A lot of them, a lot of this information travels to the spinal cord, the spinal nerves, where the spinal cord acts as an integration center for that. Many can be also interpreted by the brain itself. Some of us can be conveyed to the brain via the cranial nerves, but there's kind of a mix here. So a lot through spinal nerves, also through some cranial nerves. And then this is in contrast to the specialist. And so when we think of the special senses, these are the, the big five that we think of. So safe, so smell, taste, hearing, and vision. Within this, we can also have, we also have the capacity through balance of affecting acceleration and velocity. So something, those things for the special, These are housed within very complex, complex sense organs that have a sole function of only being sensitive to a certain type of stimuli. And these are mainly interpreted by the brain, where the brain will act as an integration center when they're tied to reflex arc. A lot of times these are not tied to reflect art. Being able to appreciate a piece of music, no way shape or form associated with a reflex arc. But being able to respond to say a very loud suddenly found that IF associated with the reflex arc. And in these cases, especially when we're dealing with, are special fund to the brain and typically the integrations into fourths. So when we talk about receiving a thing, I'm thinking of stimulus. We have two distinct ways that this can be set up. In general, what we can have is an actual neuron it felt. So in this case we have the neuron itself that has receptor protein and the dendrite. And at when the stimulus, whatever it may be, reaches or interacts with the receptor protein. If there's enough interaction or enough of a, of a high signal strength, then that will cause a depolarization, will cause a graded potential, which will then, if it's strong enough to cause an action potential. And then off we go sending a signal down. Down to the integration center. So this is when we're dealing with a neuron that it felt sensitive to a particular stimulus. What we can also have is we can have a actual specialized sensory felt. And the sensory cell can be sensitive to stimulus. So it has a receptor protein that it, that it stimulated by or is activated by a stimulus. And this can then Cobb depolarizations within that fell. If there's indefinitely depolarization, it will cause an action potential. And then this will cause this sensory cell to dump a neurotransmitter. Then if enough neurotransmitters dumped into the synaptic cleft, then this will cause a change in membrane potential in the neuron and the dendrite of a neuron, if there's enough of a change in membrane potential, will have a graded potential. And then off we go generating an action potential. So we can have a neuron itself is sensitive to stimulus, or we can have the sensory cell that it's sensitive to stimuli that is stimulated, that can be activated by the stimulus. And then it will activate an adjacent neuron and adjacent dendrite of a neuron. So now that we're see the different ways, the general steps for this, let's look at how there's distinct ways that a stimulus can cause a change in membrane potential of a cell, whether it be when it, when it attached, but it's a part of a dendrite of a neuron. Or if we're just dealing with a specialized sensory cell just by itself. So let's look at the two distinct ways that they fell. Voltage without a fellow member potential can be impacted by stimulus. And so we have two distinct mechanisms here. We have ionotropic signal transduction or metabotropic signal transduction. Both of these occur fairly rapidly, but when it's much faster than the other. So, and both of these diagrams and buffalo figures, that blue dot is the stimulus. So with ionotropic signal transduction, what happened with the stimulus itself will directly open or close an ion channel, and this will cause change in membrane potential. With this change in membrane potential is strong enough, this graded potentials strong enough, it will cause an action potential. Now this is vs r metabotropic signal transduction. With our metabotropic, it is slower because what happened is the stimulus will interact with a membrane-bound protein, which will then cause a whole small chain of events to occur inside of the cell, which will then eventually open or close an ion channel, which will then cause a change in membrane potential. And if this is strong enough that this graded potential strong enough, then we have an action potential. So stimulus we'll call this the fears of events to occur. And then it will have a change in membrane potential versus the stimulus directly causing a change. Tension, OK. When occurs very rapidly, one takes much longer to, to, to react to stimulus because of all the steps associated with it. And comparing the two ionotropic, very, very rapid. Yet again, that stimulus directly opens an ion channel. Typically it can't. There are some instances working close an ion channel, but typically it opened them. And with this, we have a whole host of things that work this way are stimuli that can activate ionotropic. Can, stimuli that can, that can cause changes in membrane potential and in sensory cells. Different types of stigma. So we have pressure is one type of stimuli that works throughout the tropics, signal transduction. Vibration, temperature, small ions, what this way. So if we think of say, temperature vibration, what happens is that think of a cell or cell of the 3D structure as we press upon that fell and we start to stretch it out because we're pressing upon it, were physically opening up gate, opening up channels, allowing ions and inept. At that temperature. There are certain gates that are temperature sensitive so as they undergo certain extremes of temperature, So-called gates to open or in some cases with close causing ion come in around causing changes. Remember potential. If these change, remember to potential, these graded potentials are strong enough, will have an action potential versus our metabotropic signal transduction. So get again, these are much slower and the stimulus will cause some type of cascade of reactions to occur within the cell, which will eventually, typically open an ion channel. Sometimes it can close it. And with this, a lot of chemical detection occurs this way, especially when we're dealing with very large complex chemicals. Or walk there large solid. So this is, say comparing individual ions, just sodium versus a glucose molecule, okay? Chloride versus an entire amino acid. For instance. Although with this, with metabotropic signal transduction, we can assess very odd or almost, almost invisible, not really visible, but, but very, very odd types of stimuli such as photon, like tweaking, we can sense light through this. And this is how the retina as work until when we, when we're comparing the special senses we'll get into later. But hearing works on ionotropic signal transduction for wild vision works. I'm metabotropic signal, signal transduction. Light travels faster, but our capacity to affect light versus sound, we can assess, found much faster than we can affect light. So we're more rapidly stimulated by sound waves as opposed to photons. And this is because photons use metabotropic signal transduction versus sound waves set off ionotropic signal transduction. And we'll see the distinctions as we move forward. So let's talk a little bit about some of the general language associated with fancy receptors. And so each receptor had the characteristics sensitivity. What it is, what type of stimulus will set this receptor off? Your eyes cannot be set, can't be stimulated by found width. Or your taste buds cannot be stimulated by light, that sort of thing. And so because of this characteristic sensitivity, we have receptors specifically. And so this was due to the accessory cells are structures within the receptor as a whole that make it sensitive to a particular stimulus. Okay? So I already gave some examples of this. So say for example, we're dealing with free nerve endings. These are very simple receptors and these are respond to a variety of stimuli. So these can respond to temperature, pressure, things of that nature, versus photoreceptors in the retina that only, that or only sensitive to photons. Nothing else just set them off. Families won't set them off. Temperature one set them off, but only photons and particular photons of a particular wavelength as well. So let's talk about the sensitivity of receptors. And so the region where a receptor can stimuli, this is its receptive field. And so that typically have to do with physically the thigh or the spread of those receptors. If they occur in a very small area, very, very large bay. Okay. So for example, here we have, we're comparing the lips versus the back. Okay? We can see that these touch receptors on the back have very wide, wide, sprawling dendrites versus those in the skin are very, have very small, very small width of their dendrites, but also that they're occurring at much higher density. Okay? So per unit, unit space, there's more, more receptors present here on the left versus on the back. Okay? And so what this does is that this allows for distinctions and the localization of the stimulus where the stimulus coming from. Alright? And this is tied to the site through stuff to field. So we can have low acuity or high acuity. Or high acuity is where we have the capacity to really pinpoint very carefully where stimulus is coming thing versus low acuity that we have very large receptive fields. So we just kind of ballpark and we know it's around here somewhere, but we really can't assess. Finally, exactly words where that's coming from. So the classic example of this, which is what this figure is showing, is if you take some, some pink calipers and you touch them up, you have a persons, the person who's being touched by this calpers that closed arrive. You press the little, these two needle again, jet ligand flipped. And if you're in a place with very hot the level of acuity, you can you can pinpoint and high accuracy where the tips of those pins are touching, whether it be on the faith, the lit, the palm of the hand, etc.. But if you take the same device and you brush it up against our push, gently pressed up against somebody back. They lacked. 32 to have that same level of detail is as far as being able to tell exactly where those two pins are, I can tell you a region where, where it's being stimulated. They can't they can't tell you the exact distance between those pinprick. Okay. And, and that's one way of looking at acuity where when you have low acuity faith getting your back, you know that that general areas being stimulated but you can't pinpointed versus places high acuity. If your receptors are very close together, you have a high density of receptors than Therefore they have very small receptive fields. You can pinpoint, you can find the location of that stimulus. They're very rapidly with high fidelity. Now, along with this, we have different functions or different functional classes of receptors. And so with this, we have the capacity to filter out constant stimulus. Okay? Think of it this way. When you sit in a chair, you don't constantly, you're there comes a point where the feeling of the chair up against your back kinda becomes almost background noise. You're not thinking that you're sitting in a chair or say when you put on clothing, there comes to there comes a point where you no longer thinking about the underwear that you're wearing unless you're really concentrate or let you shifted. If you wear glasses when you put your glasses on in the morning, then as they progress because you don't feel that they're there until, say they shift for some reason the slide down your face or, or what have you. Or another example of adaptation is if you're in a room or you're in the kitchen and you burn. Okay. After being in that room for long enough, you no longer smell that burnt toast. But if somebody comes, if a person comes into the kitchen and who was not around that toasts when you, when you burn it, they say, Hey, who are toast or say when somebody prints popcorn, for example, microwave popcorn, that super supreme stench you become. You show adaptation to that stimuli if you're exposed to prolonged periods of time. But if you're new to that stimuli than it's fresh and new and you react to it. And so what adaptation is the actual when we're talking about adaptation to a stimuli. So with this, we're dealing with reduction in sensitivity due to a constant stimulus. With this, we can have different ways of setting this. So we can have peripheral adaptation. And so this deals with the nature of the receptors themselves. Or we can have central adaptation. And so with this, we have, this occurs within the central nervous system itself. So central adaptations, a little more complex. And what this is is that the brain itself or the spinal cord is, becomes initially where that stimulus. But then as if the stimulus is continuously applied, awareness of it will, will dissipate. This occurs within the central nervous system again, so put the brain with the spinal cord. But what we typically see is peripheral adaptation. So a peripheral adaptation, the, there are different classes of, of fence receptors that are found within the body that are sensitive to different types of stimuli. And so with this, we have fact adapting receptors and slow adapting receptors. So fact adapting receptors, these are also known as phasic receptors and a slow adapting receptors. These are also known as tonic receptors. And so with a fact, adapting receptors are phasic receptors respond strongly at first, and then that response to climbs to the stimuli. Slow adapting receptors show a little to no adaptation. But over time that reduces, it reduces that, that, that, um, that receptivity to, to, to the signal. So we have a slow slope, I'll die off of, of, of, of response to that stimuli. So when, but to think of if. So, here we have our phase and here we have our tonic. And so what we have here, so we're comparing the two. So this is the actual receptor potential. This is the receptor potential for photonic receptors, the receptor potential for the phasic receptor. And this will be a neuron that is being stimulated from this receptor. Okay? This is the eighth neuron that's being stimulated by this receptor. And then this is the stimulus that's being applied to both of these classes of receptors. But the phasic end to the tonic. So we apply stimulus, the stimulus stayed on and we take this HTML5. Okay? So with our favorite receptor or fact adapting, we sense the stimuli and then it just, we stop. Then it stops. It stops responding to it until we have a change in state, and then we respond to it. So you can think of phasic receptors at on-off switches. We own these only really go off when there's a change in state, when, when a stimulus is applied and then a stimulus is taken away. Tonic receptors, these are slowly adapting receptors. And what happens is, as the stem is continuously applied, they will reduce the frequency that they fire. They will reduce their frequency of action potentials due to the stimulus, thereby reducing the, the frequency of action potentials traveling along the effort. Okay, so eventually, as time progresses, they slowly, they slowly stop responding to that stimulus versus phase. That is, the response to an a, the beginning of the stimulus and the end of the stimulus is where we get that flurry of activity at the beginning and at the end versus tonic to slowly died. That photonic can be, if you wanted to be crude about it. Facebook is like an on-off switch where the stimulus happens with stimulus stops happening versus tonic receptors, almost like a a dimmer switch. So ways of thinking of this. So 3EI that get against kind of on and off tonic is we're looking at the intensity wanes over time. And so with favor on and off odors and a good example of this temperature. So say if you're traveling between buildings, are traveling from different from true. When you enter a room where there's a temperature differential, u note that immediately when you enter the room. But once you've been in that room for a long period of time, you no longer notice that it is that it is colder or warmer than that preceded room. Ok. You only send that initial change in temperature that we're dealing with an extreme. But a line for temperature. You're in that room, you only really fit when she entered that we're painting a touch. So think of wearing clothing, for example, that's when I went 11 example of that. And also odors. When you first encounter an odor, typically that stepped off these receptors, but then as that odors ever present in that room and no longer sets off those receptors until it completely is removed. Per tonic receptors. So yet again, he doesn't pretend that equal. So we have lowered intensity as time progresses. So with this, we see responds to pressure, for example, or even like when you go into a dark group, when you first. So if you go into a dark room and you turn on a match immediately at that first moment that liked from that match is supremely intent. But as you start to undergo adaptation to that stimulus, the intensity that you're sensing that's being relayed from that, from that match decreases over time slowly. So at the distinction between, say, the tonic receptors. So when we're looking at general senses, we can classify them in a bunch of different ways. We can classify a general sense based on where it's coming from. So we can look at if it's an extra receptor, then it's going to be stimuli from the external environment. So temperature, pressure on the outside. But are we going to proprioceptors? These yet again, since the position of the body. So by fen-phen thing, the contraction of skeletal muscle, the stretching of the joint capsules such that K, This gives us a perception of where the limbs are and how they're, how they're moving. Then we have a whole host of terror receptors, these receptors within the body. So these do a whole variety of things. From assessing pressures to assessing even temperature within the, within the body as well, chemical levels, things of that nature. And then we can also classify general senses by the type of stimulus that we're looking at, how we categorize it so we can have no sir, nociceptors. So the physical sensation of pain. So extreme stimuli will set these receptors off. So anything that would cause tissue damage of stream temperature, pressure, these will cause, this will set off these announcer receptors. We have thermo receptors. These are sensitive to changes in temperature. So we find these within the thalamus and hypothalamus. We find me on the exterior of the body. Yet again, we're not dealing with at a specific temperature, but these are sensitive to changes in temperature. And then we have mechano receptors. These are sensitive to physical distortions in cell membranes. If you think of a film membrane as we were putting pressure on it, as we stretch it out or quench it down, we're changing the shape of the cell membrane, which then will, can, if there's the proper receptors on the membrane, open and close. Ion channels allow ions in or out, thereby causing changes member to potential, et cetera, et cetera. And then finally we have chemo receptors. So these are sensing chemical composition, the chemical composition of body fluids, so changes and chemical, chemical compositions of things like the partial pressures of gases, month, glucose, PAH, things of that nature. That's just kind of looking a little closer at some of the different categories. So we have our notes to receptors. These are the two extremes of extreme states. So anything that would damage and it worked who fell, kill, felt. And so these nosy receptors, they are sensitive to extreme temperatures. There. Physical damage 68 and you get hit by a baseball, the causes breathing. Okay. That that does nosy receptors that gets set off. The physical damage can or does damage to self can, can release chemicals from these into itself. And so these can also send off these nociceptors. So say if you have internal pain from something, fe internal pain due to a kidney stone or something like that or gallbladder stone, back pain due to say fell becoming damage and sending out chemicals due to them becoming damage or lighting. This can set off these receptors. And then yet again, a very strong stimuli can set up all three. If it's a, if it's a stimuli that strong enough to just outright kill felt, it can, it can set off nasa receptors that are that are sensitive to temperature. Receptors that are sensitive to physical damage, or no, sir. Receptors that are sensitive to chemicals from, from injured self. When we're talking about pain reception, there's different categories of pain and fill with just a small list to leave. So we have that pain, slow pain and referred pain and fill with it's fast pain or prickly pain. These are sufficient to reach the central nervous system very quickly that so reach the brain or spinal cord very quickly. These are associated with very deep cuff versus slow pain or burning pain. This is long lasting, slower reaching, kind of crawling up, you kind of pain. So the either have a delayed onset but these last longer. So if the kind of the so for example, if your family and your hand, that initial pain, that fact pain, this is what we you immediately feel. The importance of this is the following. There's kind of the thought behind these two distinct categories. The pan or the following fact pane is would stop, stops you from continuing the action immediately. Okay. So you're cutting some vegetables. The moment you Cut into your own flesh by accident. That fact painting tells you, makes you aware of that damage and helps your activity. Then once that fat paint has come and gone, then you have slow pain coming from that region. So that flow pain associated with a thin injury, it's the late onset last longer and this lets you be aware that that digit, that region of your foot, whatever that got injured if injured. So you can kind of we should stay off of it. So kind of act as a way of of not further, further damaging that limb upended what have you because it's already damaged, makes you aware that that have that some type of damage are then referred pain that goes onto these. So this is where we can have pain in a visceral organ manifests itself as coming from another region. And so with this, say for example, a great example of this with a heart issue. So if you're having a heart attack, for example, the classic, not in most cases, not all cases. In most cases. Pane on the left, radiating pain on the left side of the body and the chest. This happens in some heart attacks. All heart attack. So just be aware that if you're having pain in the liver and the gallbladder, you'll fence it below the right, the right portion of diaphragm and on the right shoulder, the ureters. So say if you had a kidney stone path into your ureters along the hips, you'll feel a massive amount of pain. Pain in the stomach, right? Both bipolar and likely profit in in the small intestine right below the vitally profit. And with your colon got a general surface pain. So these are just different regions of the body that effect that will that those pain receptors also go off when there's pain perceived or sent in those visceral organs. Let's talk about thermoreceptors. So thermoreceptors exist as free nerve ending. These are found throughout the body, so that can be found in skeletal muscle and the dermis and the liver in the hypothalamus. Remember those in the hypothalamus is responsible for establishing and affecting our core body temperature. There are many more cold receptors than hot receptors. So these are receptors that are sensitive to different temperatures, okay, and went up behind that, is that when we start to really become exposed to lower and lower temperatures, we have a lot of, a lot of different mechanisms that get, that get activated from this. Vs with hot receptors. If more of well, we engage more, not just avoidance behavior, obviously sweating, but vs. cold. We have to really enact a whole bunch of mechanisms to try to maintain our body temperature. So say like burning brown adipose tissue causing thermal shivering, thermogenesis, causing a constriction of vasculature to to the Surface Pro portions of scan, things like that. I lead you to have general authentic receptors so they're sensing a change in faith. Ionotropic. So these, with these, thee. Is what's causing the opening or closing of ion channels, which will then cause changes in membrane potential. These are thermo, receptors, yet again are very active to changes in temperature, but they quickly adapt to stable temperate yourself when you enter a new room and it is much colder, much warmer, you immediately said fat and you can feel that difference. But once you're in that room for an hour, two hours, whatever, you you're no longer that aware of the batch difference in temperature at the top, the lot of engages sweating started engaging or were shivering. But when it's a just a couple of degrees, it's not the kind of thing that you're going to notice after a while of being in that room. Then we have our mechano receptors. These, these are censored, stretch centered to compression. So squeezing of cells, twisting motion, or in general just anything that will distort, physically distort the thumb membrane felt. With this, we have a whole host of ion it, these are primarily on ionotropic. Because we have our tactile receptors for touch. We have baroreceptors that are for stretch. These are associated with organs to the line organs. In particular, we can think of organ like say, the bladder, the stomach, our lungs. Add, these organs, fill with air, liquid, the food, what have you? That organ will stretch, thereby, thereby letting the brain know that that organ is filling up. And then we have corporate receptors. These receptors associated with the stretch, skin or the structure skeletal muscle stretch or of joint capsules for assessing if a lender is being engaged or not. So let's take a closer look at Tech, at these different types of touch receptors. So first let's look, attacked our receptors. So these fences of gentle, gentle touch, pressure or vibrations. So when we think of a vibration, vibration sensor, this is, say, think of something running across, could an ant, something rubbing up against the skin that what centers that is in part that vibration sensor. Okay. So with that, we have different categories of these. And with this we have that. So we have fine touch and pressure receptors. So these give very, very detailed information about location. Five, texture stimulus is if Sony Fourier rubbed up against something biting us, that sort of thing. We have crude touch receptors. So generalize information about the stimulus location is that and what quadrant of the body it is cut type of thing. And when we're looking at these tactile receptors, we have two structural passes out to distinction. So we have these an encapsulated tactile receptors and we have encapsulated tactile receptors. This will dictate what type of stimuli will affect each of them off. And we'll take a closer look at this. So looking LOW closer at some of these tactile receptors. So first, let's look at our free nerve endings. Are these are common in the dermis, very sensitive to light contact. These are an encapsulated, these are basically two dendrites. Within the dermis itself. Another, an encapsulated tactile receptors are the root helps is the root here plexus, so attached to every single hair follicle, We have an encapsulated with her tech side. So as the hair on your, on your arm is gently touch, say, an ant crawls when you're hot or something like that, that as it moves amongst the hairs on your arm, it will cause the hair the move which will then cause the hair follicle to move, thereby setting off those who were here plex five, letting you know that something is touching that care and causing it to move. We have a lamellar cop corpuscle and then we also have tactile disks and MCL disks. So glimmer lamella cool, upcycled, encapsulated. And so with this being encapsulated, will act as a filter. So what it means by encapsulated is that there is collagen surrounding this dendritic Prof. And because it's wrapped in all this college and only very, very strong or high-frequency vibrations will set off this dendrite here. So basically, the confederate felt layers surrounding it act as a filter. They filter out very, very fine, touch, very, very fine. It has to be very, very high intensity tactile, tactile stimuli that will set off these lamellar corpuscles and then are tacked on disk and Merkel, they've either been encapsulated. So with this, we have the free nerve endings with Merkel cell in the epidermis. So here the free, the free nerve endings with Merkel cells attached to them. These, while they're, while these are encapsulated, they are very sensitive to touch. And with this, what happens is the Merkel cells will then talk to the tactile and relay information that the Merkel cells that are highly, highly sensitive to have a high degree of acuity. Burgers sensitive, so sensitive to light touch with, with the skin. These are also an encapsulated, there's no material surrounding them. And so with this, we have our last two that are both encapsulated. We have a bulbous corpuscles, or also known as Ruffini obstacle. And then we have our tactile popsicle. Both neither capitalists above, these are wrapped in some type or associated with them type of connective tissue with a bulbous capsule. These are associated with dermis, associated with columns so as getting stretched. And when we think of skin stretching, we tend to think of your stretching and crack and we're not really thinking about that. We're just thinking about as they move any region of your body, that bit of skin surrounding, especially say the joints, will stretch. To accommodate that motion, yet more, Khaliji act of covering the drink and fell. And Philip at that distortion that stretching the bulbous corpuscles are offensive to that and then they get set off. As the stretching occurs. They're encapsulated because they're associated with collagen fibers within the nerve they felt with our tactile corpuscle. These are places make, these are encapsulated. But this allowed them to have a very large amount of acuity and allow them to be very sensitive to low frequency vibration. So those places with very high sensitivity fill the eyelids, lips, fingertips, nipples, and external genitalia. Fill out a high amount of acuity, high amount of sensation, and whether there's something to initial contact and low frequency vibration. And so by being encapsulated, their, their filter out continuous contact. And also it helps to filter out a high frequency vibration. So this encapsulation aid acts as a filter to, to whatever stimuli, to other types of stimuli. So let's talk about baroreceptors out that talked before. These are especially type the stretch receptors monitor the shape of an walking. Okay. And at the Oregon changes in shape typically due to pressure building up within that organ. Think of your bladder filling with urine. Ok. It is that urine is exerting pressure against the bladder that is causing it to stretch. The amount of stretch the baroreceptor center is correlated to the amount of urine in the bladder. So we TVs and the colon digestive tract. These are imperative in the test and the digestive track because as food enters or ingest a food and just it travels through the gastrointestinal system. It will sit off different regions solely due to stretching that region as material enters. So add the food bolus enters the stomach. There's stretch receptors like off the start the production of hydrochloric acid that start the production of pepsinogen. When the duodenum stretches due to the, to the influx of time from the stomach that sets up a whole series of, of mechanisms as well. And then we also have the carotid artery we've talked about that wouldn't a lot. So the bearer receptors within the carotid artery affecting blood pressure. We also seem to me that the juggler and the aortic arch, sorry, from the lungs. So one of the metrics of how hard we are breathing is the relative amount of stretch that the lungs are experiencing as we breathe deeply. This was typically non titled breathing that we, that we see are stretch receptors in the lungs being really important for assessing what's going on. Okay, and then we'll talk about proprioceptors. So with this yet again, we've mentioned this before. This is monitoring the position of joints. So these are free nerve endings within the joint capsule themselves. So add that dies, that is being engaged. It will stimulate these free nerve endings, letting you know that that has been activated towards moving or not moving. In some cases. They've also aid in monitoring tension within the tendons and ligaments as well. So there's some there as well. So we have these Golgi tendon organs which are specifically and attendance. We also have our muscle spindles which fall within this category as well. So these are the receptors in skeletal muscle that monitor structure, that monetary contraction and stretching of, of the muscle fiber itself with the hope and width. This this type of proprioception becomes integrated with sensory information coming from the interviewer about balance. And so this is where we not only use visual information and information from the, from the inner ear about just general balance. So are we upside down or not kind of general balance? But then we can use this proprioception information as well to aid and smoothing of motion. Or just plain old just maintaining balanced and walking in a straight line. Alright. So all these can be become integrated with multiple systems to achieve certain goals. And then we have a whole host of can kinda chemo receptors within the body. These are typically metabotropic in nature because they typically are sensitive to very large complex compounds. They, sugars, for example. Felonies can detect very small changes in the concentration of chemical, sometimes in the interstitial fluid, sometimes in the plasma, sometimes the cerebral spinal fluid and finance synovial fluid, all these different fluid as it travels through the body, undergoes rate to the exchange. And they can respond to water soluble in lipid soluble compounds, so polar and non-polar and some examples of what can be found. So the rescue tours of the medulla oblongata, nothing. Partial pressure of oxygen and CO2 PH of the blood that's traveling through here. We also have the body, so we have the carotid bodies in the aorta got OR aortic body. These are sense, especially in the composition of blood traveling through. And that just image medullary region of the nephron. We have a whole host of chemo receptors. They're assessing the composition of the filtrate, for example. So there's a ton of these throughout the body. So let's talk about the special senses. These are distinct from the general senses because the receptors for these, for these stimuli are house and very complex sense organs that have high, high, very, very high degrees of success. For that stimulus. You can't use your tongue to send photons, okay? Your ears can't. Flavors that sort of thing. Also note that these are mainly interpreted by the brain. They are tied to some simple reflex arcs. But for the most part, these are interpreted by the brain, the stimulus as interpreted by the brain. And the majority of this is for higher water level thinking. So this is more for, oh, let me remember what this type of plant looks like, where I can distinguish from one plant versus another. Some of these are tied to reflex arcs, but the majority of it is higher level thinking, higher-order thinking. So when we're thinking, we're looking at the special senses that the Big five, we're looking at female olfaction, looking at taped gustation. We're looking at balance Schmidt fellow ratio, also technically velocity should be incorporated with that as well. Looking at hearing and also vision. So let's go one by 11 by one. So I'll probably relatively the simplest of them all. Let's look at olfaction and so width, if these are the olfactory sensory neuron, these form the olfactory nerve. Ok. Remember that the olfactory nerve sits within the cribriform plate of the ethmoid bone. Alright. And so when we're looking at the roof of the nasal cavity, this is where the sensory epithelium exists for the olfactory system as a whole. And so with this, we have these cilia that project be slightly beyond epithelium and into the nasal cavity and then at odorants, so particle that are floating within the air travel is odorants come, come against the surface, bind and they will set off certain receptors. And so the cilia that are exposed, these are covered with mucus from the olfactory gland. This mucus have a variety of purposes to protect these the sensory cells from being damaged. But also this acts kind of like flypaper, allowing the orange to bind to the philia and also to some degree, depending upon the nature of the odorant, allowed the odor to kind of stick around for a little while, while it encounters cilia that, that will be set off by it. The really, really interesting thing about olfaction is that this is the only region of the body, only, only original body that an adult. We have. Regeneration of neurons. They're very, very, very, very slow. But it is possible and that does happen. For instance, you see this? When somebody quit smoking, for example, they will slowly rebuild UP their sense of taste and smell are granted. The thing to note is that a lot of flavors that we, a lot of things that we interpret as flavours are actually related to smells as we're eating certain types of food. So things like say, for example, a lot of the perception of that is more based on the olfactory cue. It's not really what the tongue is doing with that food, for example. And so we have these regenerative basal cells in the olfactory epithelium that replace these sensory cells. And so with us, the olfactory path with what we have, we have axons from the fill factor receptors lead the olfactory epithelium through the cribriform foramina. So yet again, going through the cribriform plate itself and the synapse onto neurons in the olfactory bulb. So remember yet again that our olfactory nerve is very, very short, is the shortest of the cranial nerves that just emanates through the cribriform plate. And then once it, once it enervates with the olfactory bulb that hit done, that's all there is to it. Then add the olfactory bulb is stimulated than it sends information down through the olfactory tract to the cerebral cortex, hypothalamus, and to regions of the limbic system as well. So let's take a closer look at this. And so here, what we're looking at. So this is the, so what we have here is the cribriform plate. So that is the ethmoid bone itself. Okay. Here we have the for, for a mean and going to the olfactory bulb so that the actual olfactory nerve fibers. And here we can see these different neurons that make up these olfactory nerves here jetting out into the olfactory epithelium. Note that here we have an active one. Here we have an active one, but here we have a developing olfactory sensory neuron. You get again, the only reason the body where in an adult human we have regeneration of neurons. In part because these are the most exposed neuron in the body. The neurons are on the front line. What? The only thing you think of any other neuron in the body, it's covered in multiple, at least minimally, multiple, multiple cell layers. These are in the upper region of your notes. Okay. In your nasal cavity to sticking out within the mucus method, that's the only protection they have leave to be able to continue to smell throughout our lives. We have to be able to replace these, these neurons. And this is the only way we can get around that and fill these olfactory sensory neurons are constantly being replaced ad they literally wear out, become damaged due to just being exposed to materials. They will desiccate things of that nature. And so with this we have, we have a whole host of supporting felt. So these large supporting felt here are also ciliated and aid in and maintaining the mucus layer as well. We have a Bayes law epithelial felt that, that aid in supporting the system as well within the lamina propria, We have these developing sensory neurons that are talked about as well. And then we have all these olfactory glands that produce the mucus that bathe the cilia of the olfactory neurons. So we have all this up support tissue in place keeping everything happy. Yet again, just to kind of look at this again, remember, for olfaction we have odorants which are molecules floating in the air come in. They come in, they become associated with with the olfactory epithelium and then they interact with the cilia on these olfactory neurons. Note that the way this works is metabotropic to signal transduction. We're dealing with these odorants that are very, very large, very, very complex compounds. And so these will bind to an odorant receptor protein on the surface of the olfactory receptor cells. And these are all factory receptor neurons. And then this will cause the signal transduction pathway. Look at all the stuff that's happening which will finally open an ion channel, which will then cause a graded potential and that create a particularly strong to cause an action potential. You know, look at all these different steps. If this is ionotropic, what would happen? And we'll see some examples of ionotropic. This is ionotropic, that odor, odor would immediately opener. So that's order would immediately open the sodium gate or it may immediately openness calcium game okay, would cause a change in membrane potential directly. But look at all these steps here in this metabotropic signal transduction that occurs with olfaction is why this why the sensation of smell or something smells as an immediate, there's a little bit of a delay in that. So now let's talk about gustation, sense of taste. So we're talking about gustation that's really revolve around the dorsal surface of the tongue and the different papillae that are found on the dorsal surface of the tongue. The logistician allowed us to do. It allows us to the characterize the food that we're eating and the liquid that we're consuming as well. And that has a variety of purposes. Sometimes with aids in satiating certain drives that we have from the brain. Faith, for example, or thirst, right? When we're thirsty, what quenches or thirst is? The water receptors within our fairing. Having access to water, okay, once these are exposed to water, let's let the brain know, oh, we have drink water or we have consumed something with a high water content. For now eventually a, We won't be a dehydrate. The reason why it's important to have had to have the capacity. One thing the incidence of a thirst are either too that if you, if you are thirsty and you need to ingest water, by the time you, by the time the water that you drink results in a change in your hydration state. A very large, a relatively large amount of time has passed. And so you may no longer be be Thursday or you may continue to drink, which is also detrimental. You can't drink too much water. Aka that in theory could lead to other issues. And so by having the capacity to send the composition are rudimentary, Liddy. Since the composition. Next, the mouth we can face sheets or needs to say if we have low blood sugar, we searched for something sweet for example. Or say if we have a flight ion unbalance due to sweating a lot. We sometimes pick up salty foods, things like that. So that aid in satiating those needs are and he's trying to meet those needs to some degree. And we do that. We can assess happening through gestation. Also distinction is really important for defending us against things that could potentially be toxic or food that have split. Our gag reflex allows us. If something is rotten. We take these very, very bitter compounds that are produced by Bye, by the, by rancid food. And that causes this to, to wherever. That's cool. I mean, it can be called a wretched response, where we want to spit it out and then even vomited if we consume enough of it to protect ourselves from eating something that has spoiled. Also a lot of toxic compounds, they're very bitter. And so by limiting our ingestion of bitter substances were left likely to poison ourselves. Okay. Now granted, modern man, we search out these bitter compounds. If you feel like IPA, if you like cigars, wine, chocolate, those would give these compound that was distinctive. Notes, are these mile or these compounds that are related to toxic compounds, coffee, okay, very, very bitter compounds are traditionally come from alkaloids which are generally toxic. Ok. And so with this we have our different lingual papillae. With this we have a Philip on papillae. This papillae mainly serves to give them a break. Goodness to our tongue thing, just like the tongue of the cat. Okay, there for Philip formed a pit papillae are much larger than ours, a little stiffer, but if the same thing, this give a, a rigidity or gif give a, increases the surface area, the tongue and allows the tongue to manipulate food. So an easy way to feel your papillae is if you rub your, your tongue gently across your, your, your advisors, you can feel those papillae kind of moving along. And that's what allows us to manipulate food within the oral cavity to form the food bolus thought all these other papillae do have a role in generating some, some degree of friction because they do have some some process that he's getting out of them. But all these others, the valley, the fully fund you form. All these have taste receptors associated with them. And these gustatory receptors are aligned, are tuned to vary types of flavors. And so we're talking about the station taste. We have basically five classes of tastes. So we have salty, sweet, sour, bitter. And when that's called mommy or savory. And so width, if these are different categories of foods, different categories of components of food, so macronutrients within food. And so with this one, we're looking at the distribution of these gestation of these taste centers. So with this, what we typically see in the front of the, front of the tongue, we typically see salty and sweet, and we also have some sour. But toward the base of the tongue, this is where we see are bitter. Taste receptors as well. Also note that we fence water within the pharynx. And so this water sensation or the capacity to sense water content. This is under the purview of the vagus nerve versus we see the glossopharyngeal and the facial nerve enervating our main tape or true taste buds associated with the tub. So the wave, these are set up is, so looking here, so here's a taste, but for example, here's a valley pillai. And within these crypts, we have these taste buds. Remember back to when we were talking about the gastrointestinal system. So remember our salivary glands produce, we produce lingual lipase and the salivary amylase, the enzyme aid and breaking down food a little bit chemically, mainly so that we can take advantage of that and assess its composition such that if it have sweet, salty component to it. And so as we start to chew on food, or if it's something that's powdery in liquid form, the food will enter these scripts and then associate it. And set off. Our different tastes are taped hairs on the taste but tough. So here the taste bud. Here's report of an opening where the, where the gustatory epithelia fall juts out in a sense attentive to a particular type of flavorings are taped. And then here we just have transitional solved that aid in supporting the structure here. And so with this, we also see a different threshold for different types of flavors. And so for pleasant stimuli, we have a very high threshold, especially when you're young. So for example, there's some habituation to this as well. Have some degree. But we can eat a high amount of salty foods or high amount of, we're not as sensitive to salty foods or sweet foods, for example. Okay, that's where we have a very high threshold for pleasant stimuli. We can eat those in large amounts and we're not offensive to them. Versus unpleasant team like bidder component, we're very, very sensitive, so we have a very low threshold. It doesn't take a lot of a bitter substance to set off these taste buds. Think of it this way. Think of it. Think of a little bit of sugar versus a dropped coffee on your tongue, okay, that drop of coffee and your tongue, you sense that very strongly, very immediately, versus little bit sugar, a little bit of salt. It's not as potent on your taste buds or on the tongue. A little bit about bitter component. So when we look at our different classes of flavors, they have different types of receptors. Somebody's act upon how ionotropic signal transduction and some of these have metabotropic signal transduction. And thought we're seeing here is a taste receptor cell and what it is sensitive to. So here we have salty, sour water works very similar to to shower. And so for something salty, the primary salt that we see is sodium chloride. Sodium chloride will dissolve into sodium chloride ions. It is the sodium ion itself from the salt. That is the stimulus that enters the cell. And thereby causing a small change in membrane potential, carving calcium to come in, causing an action potential, causing neurotransmitters to be released. Same thing with, with power, power things due to acid. So when an acid is dissolved in water, the hydrogen ion disassociate itself from, from, from the rest of the acid. And so it will release hydrogen ions. So these hydrogen ions will come in. They will actually block the release of calcium ions. And this will cause a change in membrane potential, thereby causing these calcium channels to open, causing an action potential causing the release of neurotransmitters. Yet again, ionotropic because the stimulus is directly causing a change in membrane potential. Water acts very similar to the shower wall. When there's enough water, some water will dissociate to hydrogen ions, and then that will be a theft by the, by the water. Something. Sensors in the, in the back of the tongue and the fan and the, and the facts and the legs. So let's look at our metabotropic. So with this we have sweet, bitter and umami. So the sweep, we have very, very large compounds. So think of the variable very large sugars or sugar alcohols. Okay, these are Berber suite also some amino acids are very sweet. Say for example, phenyl annually is a sweet tasting amino acid. A lot of our artificial sweeteners are actually amino acids, that particular phenylalanine. And so with this, we have the sweet molecule off this membrane-bound protein, and then we have an entire chain of events occurring within the cell. And finally, we open a voltage gated channel causing a change in membrane potential. And then in the synapse we secrete a neurotransmitter. Bitter compounds. They're very large organic molecules. February large ring their, their big. Yet again, we're dealing with signal transduction pathways where we are setting off a chain of events which will then open or close a member potential, a memory channel, causing a change in membrane potential, causing an action potential. Umami, the favourite, favourite, favorite flavor. There's a lot of things that will fit the thought. Certain amino acids will do this. Certain fatty acids will do this to some degree as well. One compound that there's a lot of, there's no debate, it's completely safe compound, but unfortunately some things become targeted just due to blatant racism. Monosodium glutamate. Msg is a compound that sets off umami taste, but it is a naturally occurring compound. But it's also found in a lot of Asian cooking. And so there's a lot of anti-aging sentiment as associated with MSG. But MSG is complete. A natural man got, don't go eat an entire bowl of it, but it's completely fix. Anything that is quote-unquote, savory. Have MSG in it. Okay, if you've ever eaten Cool Ranch Doritos, what makes them so good as the MSU that gets added to it. Mushrooms have, have MSG, soy sauce has MSG. And so anything that with that kind of February approach, one of the major compound that gives it that that profile is monosodium good, right? Or MSG. So it is completely faith. For whatever reason, people are racist and they associate it. They associate Asian food that typically have that as an ingredient with something bad. And, you know, people are dumb. But look at most foods, especially any kind of snack food. Literally anything that tastes pretty good typically has monosodium glutamate added to it because in small amounts, glitches and large amounts just becomes overpowering. So that is the station itself. So let's look at the pathway of the gustatory information that comes in. So food comes into the mouth either through liquid form, where solid we, we act upon it, we chew it, we cover the saliva. Some enzymes activate upon it. We break it down into smaller bits, and then these dissolved chemicals will come into contact with the microbial IN stimuli stimulate certain. Then those impulses generated by those specific receptors will travel along particular nerves. So we have the facial nerve and the glossopharyngeal nerve being the main tongue nerves are vagus nerve have a role to play in water sensation and some bitter receptors are associated with it as well. And it is primarily bitter receptors that are really get activated or become heightened sensitivity. Someone's already ill or systems pregnant, for example. These become more heightened. And so with this, we also have the capacity for sensing other types of flavors that aren't specifically associated with the dorsal portion of the tongue. And when I'm when I meet what I mean by Kenneth and cooling. Okay. So remember spiking If this is due to kept faith into this was founded chili peppers for example, and cooling. This is due to amend Paul that found in certain plants like they MIT over different variety of the mint, have menthol in it and it's cooling or heat sensation. This is sent by the trigeminal nerves, which have receptors on the side of the mouth and also on the side of the tongue. For these types of, of, of compounds and islands, we have stimulation of our taste receptors. We have this information kind of basically ping pong through to the brain. And so we have a first-order synapses. Go first to the Psalter nuclei within the do lamda got up. Then we have our second order synapses occur in the thalamus. And then R. Then we have third order arriving the gustatory cortex. So this all to a nucleus is mainly for bringing this information in from different types of, of flavors and then combining it and then bringing it to the south. The second-order synapses that travel to the thalamus, the ether associated with creating specific drive. So a thirst drive, a drive for something sweet. These, that information becomes too, comes to the thalamus and then stops that third strike, stopped that drive for something salty or something sweet. Okay? And then finally, information going to the desultory cortex. This is where we have refined appreciation for that, for the total composition of that food item. This is where we get nuance of different types of vegetable material, different, different Thevenin and things like that, where we start to associate preferences for different foods, finance, things of that nature. So now let's talk about equilibrium in hearing associated with this is also the capacity to sense acceleration and velocity. So, and it's all revolve around the year, specifically the inner ear itself. And so when we're looking at the year, we have three main regions. We have the external ear, which we'll talk about a little bit. So we have the oracle or the Panay, which is that the ear lobe itself. Then we have the external acoustic meatus. And we have an elastic cartilage. Does that give shape to the local or the penny? Then we have the middle ear. This is where we have transference of sound waves from the external environment. To the inner ear itself proper, within the middle ear, is where we have the smallest bones in our body, the three auditory ossicles, okay? Or are your boats. And then here we have the inert, your self or internal ear. This is where we have a variety of sensory structures that aid in fencing found and also fencing motion, body position, general acceleration. Who really cool array of both of stimuli. So let's look at our external ear. And so we have oracle itself, the ear lobe to aid in of funneling found wave into the external acoustic meatus. Or external acoustic meatus. It is just a tube into leading to the beginning of the middle ear. And so with this as being just the two things can enter this. And so the terminus glands to these produce the Rex's suramin or ear wax, which is also anti-microbial at which acts and junction with hairs that will allow things to get stuck to it and then not enter the enter the middle ear felt so that protects the middle ear from, from anything getting lodged in there or anything attack in the middle here. Delineating the ended the external ear is the tympanic membrane or competitive. So this separately external ear from the middle ear. This is what vibrate due to sound waves traveling through the air. Alright. And so sound waves travel through the air, cav, to patent, to vibrate. And then the vibration is transferred from the Tin Pan Am through the auditory ossicles to the vestibule, to that to that oval window of the interview. So That's the external. Yes. Excuse me. So here we have the middle yourself. This is air-filled. There's air within this cavity of the hold. Within this cavity we have the auditory ossicles. So this is delineated by, by the tympanic membrane and the auditory obstacle to the oval window itself. Associated with this region, we also have the auditory two, or institution to the tube. So this is the connection between the tympanic cavity and the nasal pharynx. This a1 equalizing air pressure. And so if you've ever been mirror plane and you can get pressure build up in your ear when she kinda swallow and undergoing that motion, it will relieve that pressure. Or if you've had a bad head coal that relieving the pressure within the inner ear. It's all due to drainage from the institution tube or auditory tube and fill fail when somebody has an inner ear infection. What happens is that if two becomes blocked, typically due to bacterial or mucus buildup and then some type of infection can occur causing pressure to build up in the 3G. So when we're looking at our auditory ossicles, We have three auditory ossicles. We have the malleus, incus, and stapes. Associated with these three bones. We have. Skeletal muscle. Skeletal muscle is very unique and sculpt them also aid in Bray thing. These three auditory obstacles and the event of very loud sudden noises. Note. This does not prevent hearing loss. The president through the IRS, does not prevent hearing loss due to artificially loud loud loud noises, also due to chronic exposure to loud. The IRR, the internal muscles help to stabilize the bones if there's allowed sudden noise but within a certain difficult range. And so with this we have the tensor tympani and to PDF. And these, when we're exposed to a loud noise will, will, will stiff and not, and not allow the muscles, the bones to, to vibrate as they normally would, thereby offering some protection against loud noises. But it's not there's not a reason tonight, yes. You're hearing protection. Let's look a little closer at the, at the auditory ossicles themselves. So we have malleus incus and stapes were really clever when we name stuff in biology. So with this, we have the malleus are Hammer, okay? This is the one that's attached to the tympanic membrane. Here. We can see it right here. And what does the hammer hit? A hammer and anvil and fill our next enter ERA bone is the Incas or an Belichick. Canada looks like kind of an anvil, sort of from a Wile E. Coyote cartoon to some degree. But anyhow, the malleus vibrate and cause the incus, the envelope to vibrate. And then finally, and this is the tach articulated with the stapes, which looks like a stroke that used for horse riding, for example. And fill with if the stapes is attached to the oval window of the cochlea. And throughout this entire region where we have transferring of vibration. So soundwave come then the tympanic membrane to vibrate. It causes the malaise to vibrate, the ink has to vibrate and then the stapes to vibrate. And then when the SAP vibrate, it cause of the oval window the co-pilot to vibrate, thereby train meeting that found those soundwaves. Note that yet again, air, air, once we get to the oval window, this is where now that found wave will now travel through a fluid-filled cavity. So now let's look at the inner ear itself. The interesting thing about the inner ear is that all of the sensory tissue here is encased in bone, okay, giving it rigidity. And this is interesting because due to this rigidity, it protected is very sensitive structures from damage, but also it necessitates the capacity to relieve pressure and we'll get to that in a little bit as well. And so when we're looking at the inner and the internal era, we have different a lot of, a whole host of different structures. So we have if the bony labyrinth, This is what encases the year. So this is the bony K thing of all these structures. And then we have the membranous Lamberth. This is where we have all the sensory capacity. And so we have the hairstyle with supporting felt and the endolymph itself that allow the inner ear to function. So looking a little closer at this, looking at the entire, entirety the bone Lambert, we have two distinct complexs, u, two distinct set of sensors. We have the vestibular complex. So this is where we sense motion, acceleration, velocity. And then we have the coping. The cochlea is where we found itself. Alright? But all the function fairly similar to each other. Note that these are innervated by the vestibulocochlear nerve. Also then hopefully itself. So when we're dealing with here, we have the snail shaped structure that itself, that the cochlea, two openings to the cochlea is the oval window where vibrations initially enter the space. And then just as important, we have the round window. The round window is essential because of the round window allow this wave of pressure that enters the cochlea to leave. And so what happens in short is that as this, but as a soundwave comes then causes a list of all these structures to vibrate. Then it causes a pressure wave to occur and causes vibration of the fluid within the cochlea. This vibration of fluid, that pressure wave coming in up, up, up, up and up through the cochlea to the tip, then comes back down and actually on its way down. This is when it's actually stimulating the hair cells within the cochlea. Then as it makes its way down and out, it will cause the round window to vibrate, thereby eliminating that pressure wave has travelled through the cochlea, which is really, really cool stuff. And we're looking at different regions of the inner ear. We have the capacity to different stimuli which is ruined. So within the semicircular ducts, we have the capacity for sensing by position and motion. Also is associated with the cristae within the ampullae as well. Then we have the capacity for sensing,

endocrine

In this chapter we're going to cover the endocrine system. So this is our system of long-term chronic control of the body. So in this chapter will talk about the different classes of hormones and where these hormones are made and what kind of actions they have within the body. Let's get started. So in this part, we're going to talk about the endocrine system. And so when we think of maintaining homeostasis, both the nervous and endocrine systems worked together. We've already covered this before, but with the nervous system, it produces very short-term, very specific responses where we have very particular effectors because these effectors are innervated by ethernet neurons. They are directly told what to do. This is versus the endocrine system, where typically produces very long-term generalized responses that have many target organs and tissues herself. And the reason behind this is that with the endocrine system, it will, or an endocrine gland or anything that produces a, these agents of the endocrine system hormones. These things get secreted into the bloodstream and they travel through the bloodstream. And so the, those target felt can be a multitude of different tissues. You can have one specific hormone that can impact a variety of different cells, a variety of different organs or tissues. All by just recreating this compound and have it circulate through the body. And also the range of activity can be very wide. The target fell for that hormone can be in the same organ. It could even be and an adjacent felt or could be on the complete other side of the body. So it has a very wide ranging level of control. But it, and typically slower and in general what compared to, to the nervous system. Because with the nervous system are directly causing action on a particular organ, fell tissue, what have you versus the endocrine system? We have the slight delay of this, of this compound traveling through the bloodstream, OK, thumb, these can be fairly quick. And their and their reactivity or a holiday elicit a response to say, for example, up. And if an arpanet from these can, can produce a fairly quick response. But yet again, they're much slower when compared to a direct neural control or direct neural response. And so when we're dealing with the endocrine system, it uses hormones. And so these are compounds emitted into the bloodstream, but then we'll circulate through. There's many hormones. There are many hormones that are constantly being produced. It's just what varies, is the relative level of production depending upon what's going on in the body and what happens. As these hormones travel through the bloodstream. They will bind to target felt that have specific receptors for that hormone. Also. Then that once that hormone binds to the receptor, it will elicit some type of response within that top. It can be a whole host of things. Also. One thing to keep in mind that will get talked to him a little bit is the concept of. As long as there's some compounds circulating around that fits into a receptor, that receptor will become activate. This is why we can have artificial hormones or compounds that inadvertently act as hormones. And we'll see some examples of those in a little bit. So when we think of an endocrine gland work or something that secrete hormones. We typically think of an endocrine gland that's typically a ductless organs. So here's an example of a kind of a stereotypical endocrine gland. It kinda looks grainy and appearance. Think of the appearance of the, of the adrenal gland, the pancreas. Ok. And that kind of kind of grainy texture to it. I'm not that there isn't an exact duct because it isn't literally named endocrine, that it's going to secrete things into the BOD versus exocrine was creating things outside of the body, okay, or into a cavity of the body. And so with this with a, with a stereotypical endocrine gland, Well, we have associated with a capillary bed and then it will secrete material right into this capillary bed. And then those hormones will continue to flow through the body. Hormones can also be released by a whole host of other different types of tissues primarily we see these also released by neurons as neurohormones. So they're specialized neurons that instead of just releasing a neurotransmitter, they're actually releasing a hormone into the bloodstream. We have a whole host of organs, a massive amount of organs that secondarily produce some type of hormone that's ranges from fat to the heart. Whole host of different, we're going to have a secondary endocrine function. Typically the aid in serving the needs of that, of that organ or even tissue type. And when we look at hormone, there's three main categories are three general classes of hormones that was based on what type of compounds they're made out of. And this will impact their functionality and how they behave in the body. And so our three general type of hormones are any peptide and steroid. So let's look at these little closer. So here we're comparing organs that we consider main endocrine organs. So these are Oregon that have a very large percentage of the functionality is dedicated to secrete hormones. And then we have organs with a secondary endocrine function. The primary function of your heart is not to produce hormones, but it can produce hormones. Same thing with the digestive tract. It, its primary function is not to release hormones, but it can produce hormones that actually produces a very large amount performance stuff that we'll go through some of these examples as we go through this PowerPoint. So here we can see a kind of a, just a graphical representation of, of what's going on. So everything in purple here, we can see these as primary endocrine glands versus everything here in this greenish hue. These are all organs with a secondary endocrine function. Yet again, their primary functionality is not to secrete hormones, but they will secrete hormones. So with this we have everything from adipose tissue to the heart, even the gonads. Because remember the gonads, yes, they produce, they produce sex hormones, but really their main functionality is to produce gametes. So let's talk about our different categories of hormones. Let's first talk, talk about it. Comment. So steroid hormones are derived from cholesterol because this does hormones are nonpolar, meaning that they can passively diffuse into cell membranes, no problem through cell membranes, problem or classes of steroid hormones. There's a whole host of them, but aldosterone quarters also. Our stress hormones fall into this category. Cortisol Court discussed around and things like that where these relieve inflammation, things like that. And then our sex hormones fall into this category as well, though, testosterone, which testosterone is then turned into estradiol and females. That's why these hormones and others like them that fall under this category being steroid hormones. These can be administered just to the skin. Would you think of the birth control patch that a patch of plastic impregnated with, with that, with these hormones. It, it's left on the skin and the hormone gets absorbed straight from the skin into the bloodstream. Same thing for anybody who's undergoing, say, testosterone replacement therapy. They'll they'll give them a gel that they put under there, under arm and the armpit region, which they will absorb testosterone from there. Next we have peptide hormones. These are derived from strings of amino acid. So here we have gonadotropin releasing hormone as an example, an influent, because these are derived from strings of amino acids. This is our group of hormones at the highest amount of diversity. There's, you know, if you think of your 20 amino acids and you think about combining them in different, in different ways. You get a whole litany of, of crazy combinations and to a very wide variety of hormones that can be produced that fall under this category. So here we have our last category of hormones. So these are our amine hormones. These are based off of tyrosine or trip to fan. A trip to family had melatonin. Melatonin is involved with daily activity cycles being produced by the pineal gland. From tyrosine we have are catecholamines are either firings. I had a filename, have iodine, and this is why we have nutritional requirement for iodine to allowing, allowing us to make these hormones. So we have thyroxin and try harder to fire any. These are also known as T4 and T3. So the thyroid hormones regulate metabolic rates, regulate body temperature, and they have a whole host of other downstream impacts as well with our catecholamine. So we have dopamine. Dopamine is primarily most active in the brain, where it's used as the neurotransmitter into the thing. And you'd have a signaling molecule can be used as a neurotransmitter. And a lot of them can also be used as hormone. Just depends where this ends up. If the compound has ended up in the synaptic cleft. In that case, it's just a neurotransmitter. But if this compound then get secreted into the bloodstream, then it's a hormone. We do have circulating amounts of dopamine in our bloodstream, but it's not super clear exactly what it does. I think it just kind of, if I remember correctly, it's kinda like a quote-unquote helper hormone that helps certain prophecies occur. But if it doesn't, that's not the main driver of anything, at least in the bloodstream itself than outside of the brain. And thought of brain, it. Has a whole host of things, especially say, a satiation or reward. Reflexes are impulses. But compared to that very, very standard, very well-known catecholamines, norepinephrine and epinephrine. These are released by the adrenal gland. These are the, these are the main hormones in our fight or flight response. So when you become agitated, become scared of something or under stress, the get released and the increase your capacity to in theory, flee from a situation or in theory, defend yourself from danger. These two are very fast-acting and there's a really neat system that increases the speed at which they're secreted by the adrenal gland, which we'll get to later. So let's talk about hormone synthesis itself. We will get into a lot of nitty-gritty of this. But primarily we have two ways that these lead felt when we're dealing with our anion or peptide hormones, these just leave do exocytosis. Okay. So they're, they're formed in the ref into play endoplasmic reticulum. They get packaged by the Golgi apparatus and then get dumped via some type of secretory vesicle. But when we're dealing with are, are, are steroid hormones, ours cholesterol based hormones. These can just then hopefully passively diffuse out of the cell because they are nonpolar, they can just diffuse right out. So they don't need to be packaged up into, into, into vesicles. They just get they on their own, just diffuse out ad they're formed. So how did the circulating hormones elicit responses themselves? This all depends on a hormone reaching a receptor of the proper shape and the binding together. Once a hormone binds to receptor at the proper shape, then it will elicit some type of response in that cell. And so width if so yet again, if the receptors, the receptor and the messenger fit together, then we have some type of response. So that is also known as the lock and key model. So for example, here we have a chemical messenger for certain check. It only fit this receptor so it will elicit a response in the cell. It does not fit with this receptors. It won't do anything that they felt. It doesn't fit this receptors there won't do anything. Do they felt that is the specificity of these hormones, receptors, but also due to the system hormone at least binding to the receptors that systems-level cocoa. Dumb because at longing to have a particular shape, it can fit to it. And if Kate here, here we have a whole host of substrate, and here we have a receptor of a particular shape. Note that all of these will fit into this receptor and thereby set it off. And so this opens up the door for better, for worse, for compounds to be able to set off these receptors that aren't the, the original intended compound. Now we've used the tour advantage for a lot of different things, but it does have some deleterious effects as well. And so we've used this to generate artificial hormones or hormone analogues. A lot of plants will produce compounds that act like hormones. For example, the very first birth control pill came from a Mexican yam. This plant naturally produced this, this compound that mimics female reproductive hormones. Once it finds these receptors that bind to these receptors and activate them. There's a lot of issues also with things called endocrine disrupting compounds that are compounds that are completely artificial. And these will set off hormone receptors. How much these have an impact on, on human health. The some, some level of debate, but in theory too much but can't be a good thing anyway. So, but this is how it works. So the hormones flow through the bloodstream and as they encounter receptors, if they fit to the receptor, they set off that receptor eliciting some response, right? So let's talk about the main seat of control of the endocrine system. And this is the hypothalamus and the pituitary gland. This axis, this interaction between the hypothalamus pituitary gland is the main theme of controlled the endocrine system. And so what we have is the hypothalamus within the brain connected to the pituitary gland via the infundibulum. And when we look at the pituitary gland, we have two main divisions. We have the anterior pituitary gland and the posterior pituitary gland. How the, how the hypothalamus communicates with each of these varies. But through this elicits a massive amount of control in the body. So let's take a look at some of the details of this. And so when we think of the hypothalamus exerting control over the endocrine system. It does it in three main waves which are, which are pretty need. First and foremost, the hypothalamus itself can act as an endocrine gland. And so what happens is when we're looking at our pituitary gland, pituitary gland. Remember the pituitary gland is fitting within the dura mater, within the sphenoid bone. And so we have our anterior lobe and our posterior lip. Okay. Well, we're looking at the interaction between the hypothalamus and the posterior lobe of the pituitary gland. There are two sets of neurons that extend from the hypothalamus, go through the infundibulum and their dendrites and extend into the posterior lobe with pituitary gland. It's clear these two distinct bundles of neurons where the hypothalamus acts as an endocrine gland. So basically what happens is that these neurons, when stimulated, will then produce two distinct types of formats. That it will produce antidiuretic hormone, ADH and oxytocin. And once these are released, they will go straight into the bloodstream and circulate throughout the body and fill the reason why. So the hypothalamus itself isn't directly really, isn't. The hypothalamus is releasing the, the, the posterior pituitary gland. So if the neuron that start in the hypothalamus extending all the way to the posterior lobe of the pituitary gland where they are released. So if it's basically using the posterior lobe of the pituitary gland or the puppet. And it's undergoing its control. It's, the hypothalamus is exerting its control. Vfs accreting hormones through the posterior pituitary gland. Then we have the, the interaction between the hypothalamus and the anterior pituitary gland. And so the way this work, that the anterior pituitary gland is controlled by the hypothalamus via a very small capillary bed. That the, what the hypothalamus will do this with the hypothalamus will, will produce hormones. These hormones travel a super short distance right to the anterior lobe of the pituitary gland. And those hormones will then impact the functionality of B cells within the anterior pituitary gland, which will then cause them to secrete certain performance. This is primarily the peptide hormones that are produced by the hypothalamus. But at this point, compounds produce the hormones are approved by the hypothalamus, which will then impact what the anterior pituitary gland is secreted. And yet their hormones because they actually travel through the bloodstream, just a very short amount of blood. That's a very small capillary bed going between the hypothalamus and the anterior pituitary gland, go see the film, all of it. And then finally, the hypothalamus can directly control control and adrenal gland through nervous control, through autonomic nervous system centers. And so with this, it will directly control a portion of the adrenal gland. And because of this, what it will do, it will directly control the Adrenal medulla. So the center of the adrenal gland to quickly reproduce epinephrine and norepinephrine. And this relief with epinephrine. Norepinephrine is what causes the fight or flight response. This is y. So remember, we have the hypothalamus is on the bottom. It is their right associated with the limbic system. Okay, so as our motions surge, as we are stressed out about something, if we're scared of something, that those fears, the fear will cause the hypothalamus to stimulate the adrenal gland to release epinephrine and norepinephrine. And that's where we get this link between. Say for example, if someone had a panic attack, ok? If you have a panic attack, the reason why your heart rate starts to, to rev up and your heart starts to be harder, and you start to sweat and you feel ill to your stomach, et cetera, is because due to that emotional state or mental stick that you're putting yourself then or there's some kind of external factor that's causing it that will cause a release of norepinephrine and epinephrine and that will rev up your body, getting you ready, initiating that fight or flight response. So this is where we have that connection between emotion and the physical body itself which has, which is really neat. And so this is why epinephrine, norepinephrine can be stimulated, unreleased so quickly. And it's really neat that we have these preganglionic motor fibers that go all the way from the hypothalamus to stimulate the adrenal gland to particular accumulate the met, the medulla, the adrenal gland to produce epinephrine and norepinephrine. Looking at the follow closely, more closely. So let's look at the direct control between the hypothalamus and the pituitary gland, both the anterior and posterior pituitary gland. So we can also call the pituitary gland the hypothesis. An older term, but some texts, they'll use it. So with us. Remember here we have a hypothalamus. It is attached to the pituitary gland via the infundibulum. And note that we have two distinct Kepler bacteria. We have this primary capillary plexus that extend from the hypothalamus to the anterior pituitary gland. And then we have the smaller posterior lobe, smaller capillary bed in the posterior lobe of the pituitary gland. Okay. So anything that the hypothalamus wants to secrete through the posterior pituitary gland. We have these two nuclei that each produce a particular hormone. A pair of ventricle produces oxytocin. Super optic produces a DH. And so these neurons extend from the hypothalamus, reaching all the way down into the posterior pituitary gland and the dendrite end at this capillary bed. And so through the, technically what's happening yet again is the hypothalamus is using the posterior pituitary gland and the puppet is enacting it's will through it. And it's here where we're creating these hormones directly into the bloodstream. When we compare this with tapping the anterior lobe of the anterior lobe of the pituitary gland, where the hypothalamus secretes a whole host of compounds, a whole host of hormones. These travel in this very short bloodstream, the therapist in the bloodstream and then will impact these glands right here, this tissue in the anterior pituitary gland, causing it to, to control the functionality of these tissues. And so when we're looking at, when we're comparing and adhere to the posterior pituitary gland and the interior low, it will realists relates seven peptide hormones that will then circulate through the rest of the body. The posterior lobe only releases two peptide hormones, which technically are really being released by the hypothalamus. Because hypothalamus, this stretching has some neuron stretching from it to the posterior pituitary gland. And so with this when we're looking at the hypothalamus. And so this interaction between the hypothalamus and mature pituitary gland. What happens is there are different hormones that the hypothalamus were relief. And then these hormones will impact the five distinct tissue, five distinct cell types within the anterior pituitary gland, thereby causing them to release different types of hormones. And these hormones released by the by the hypothalamus can cause, can stimulate these tissue types they felt types to release hormones will reduce the amount of hormone they were there. So we can, we can tell the felt speed up or slow down. Yet. Again, it's all this portal vessel to the secondary plexus, right? You're that small capillary bed that's associated with the five cell types. So let's kind of summarize with a little bit. And it's, it's really dramatic to see the level of control that we have here. So here we have the hypothalamus, here we have the anterior pituitary gland. Here we have the posterior pituitary gland. And note, look at all this activity that's occurring within the anterior pituitary gland versus what the posterior pituitary gland is producing. The posterior. The posterior pituitary gland is only producing oxytocin ADH. These get dumped directly into the bloodstream versus our our anterior pituitary gland. It's producing a whole host of things that's producing. Thyroid stimulating hormone, adrenocorticotropic releasing hormone, growth hormone, gonadotropin, luteinizing hormone and follicle-stimulating hormone, prolactin and melanocyte stimulating hormone to a whole host of hormones all produced by these regions of the anterior pituitary gland. So let's take a closer look at this. And so what we have here, what this is showing is our different cell or a different tissue types of the anterior pituitary gland and the hormones that they're producing. Ok, so we have a thyroid tropes producing thyroid stimulating hormone. We have a quartic the tropes producing adrenocorticotropic hormone. We're going to add a trips producing Follicle Stimulating Hormone, luteinizing hormone. We have a lack of trips producing prolactin. We have are somatic trips producing growth hormone. And again we have a tropes producing millimeter stimulating hormone. Ok? So each one of these cell types or tissue types is producing a distinct class appointments. So let's take a little closer look at this. So when we typically think of the pituitary gland, we typically only think of it as the anterior and the posterior Lopes or segments. But in reality there's a little more nuance to this. And so within the anterior lobe of the pituitary gland, we actually have very distinct regions. Within this, we have the part of the stars, which is the main region of the anterior pituitary gland. But we also have very thin sliver called the pars intermedia. Okay? This part intermediate, All that is responsible for is to creating melanocyte stimulating hormone, MSH versus the interior of the rest of the anterior pituitary gland through the pars distalless. This is producing thyroid stimulating hormone, identical tropic hormone, follicle stimulating hormone and luteinizing hormone, prolactin and growth hormone. So let's take a look at what these hormones that the anterior pituitary gland is accreting what they will ultimately do. So here we have the thyroid stimulating hormone, it's target being the thyroid gland. And this will cause are the release of thyroxin and triiodothyronine. So our thyroid hormones, which will control metabolic rate and body temperature, are adrenocorticotropic hormone. This is targeting the rest of the adrenal gland, okay? Primarily the cortex. And so this releases cortisol cornerstone quickest around. So these are glucocorticoids, Theodore stress hormones that release relief, glucose, reduce inflammation in the body. Our aid with dealing with stress. Then we have our gonadotropin. So we have a follicle stimulating hormone and luteinizing hormone. So with these, yet again, we've seen their roles in the male and female reproductive tracts. And so what we're looking at luteinizing hormone and female, it's this causes ovulation, causes the release of progesterone. So remember what luteinizing hormone does? It softens the surface of the ovary, allow in flocculation to occur and mail. It targets these interstitial cells and causes the release of testosterone and estrogen. Okay. Remember that there is some degree of of estrogen being released in the mail. It's just there's more testosterone being released and estrogen. For follicle stimulating hormone and females, what this will do is that this will cause maturation of the oocytes and release of estrogen and males and the seminiferous tubules, the mail, this stimulates sperm production, which is really neat. And so we have these two hormones impacting both male and female gonad differently. So here we have prolactin. Prolactin has a variety of roles. At, its primary role is in females, but it does up regulate the immune function of both sexes in females would have primarily is promote, stimulates the generation of milk and to stimulate the growth of the mammary glands, in particular, in preparation for pregnancy or during pregnancy, growth hormone. What this will do is that this hormone will target a whole host of self. This will stimulate lean growth in the body. So birth of skeletal muscle, okay, with the skull called is caused the animal protein so called the formation of proteins especially in skeletal muscle and will cause the catabolism of lipid. So this will cause lipid to be burned a preferentially to almost in a lot of cases, the active energy substrate, but also in some cases almost make room for extra space in the body cavity for more skeletal muscle to be laid down. And so the growth spurt that we, that we, are, that we're privy to are supposed to during puberty is primarily due to these increased levels of growth hormone that are circulating in the body. And there's other growth factors that will stimulate growth, which we won't get into, but there's a ton of ten others. And then here we have our melanocyte stimulating hormone. Very active in utero, was also active in young children. I'll, but also active in pregnant women. And some diseases will stimulate this. We see it being active in pregnant women where this causes darkening of the areola and the nipples, like before parturition or, or, or during pregnancy. So now let's talk about this posterior pituitary gland. We talked about the anterior pituitary gland and all that interaction. And yet again, in comparison to the posterior pituitary gland, it's fairly simplistic. But we really have, is we have the posterior pituitary gland being innervated by, by neurons from the hypothalamus nurse by the hypothalamus, the nerve because there's more than one neuron traveling through. And yet again, these neural hormones produced by these neurons are ADH and oxytocin. Adh is anti-diuretic hormone. So this tells the body to retain water. So this reduces the amount of water lost at the renal system and the nephrons when they're forming your. And so what this will do since we're retaining more water, this will increase blood pressure and blood volume. Oxytocin has a variety of roles that the biggest win than female, it will used to induce labor and also causes milk ejection as well. And males, especially during ***********, it will stimulate the release of prostate secretion stirred ************. So right before ***********. So there's right before ***********, there's a spike in oxytocin that will cause the release of the prostate secretion. And yet again, oxytocin is the hormone involved with pair bonding. Well, so now let's look at some of the other endocrine glands throughout the body. So first and foremost, let's look at the thyroid hormones. Thyroid has a variety of functionalities with it. Primarily we're looking at regulation of metabolism, regulation of body temperature, but also regulation of calcium levels within the body as well. So here we have the thyroid gland, right here, right? Figure two, the lyric. And with it we have the follicles. So we have this cell, so we'll look at a cross section of it. We have the follicles and within it we have the follicle cavities. So there's basically fell mixture here, width called cola. And within this colloid, This is where we have the precursors to thyroxin and try out a filing. And with it. So we have the precursors to T3 and T4. And then a scattered along here we also have the feet. Bioethics is much smaller cells. The thyristor like these produce calcitonin, which will reduce plasma, circulating plasma levels of calcium, thyroxin and trying to fire any, These are our produce also in times for increased metabolic demand. So if as you increase skeletal muscle man, these will increase as well because they have a role to play, an increasing your Meetup, your total metabolic rate in the body. So anytime we need to kind of ramp up activity in the body, these two hormones will spike. Very, very powerful hormones. Also remember that these two hormones are, have iodine in them. So this is why we have iodine. Iodine that needed mineral and our diet. Because without iodine we can't produce these hormones. So when we're looking at thyroid gland, so here we're looking at the ventral portion of the thyroid gland and we look at its posterior side. We see very, very distinct gland. So on the, on the dorsal side of the thyroid gland, we have these four little tiny para thyroid gland. These two little, these four little parathyroid gland. These are antagonistic to what's happening on the ventral side of the thyroid gland. So these parathyroid glands produce parathyroid hormone. And what this parathyroid hormone does is that it increases blood calcium ion. Okay? And so the activity, it reduces urinary excretion of calcium. It will stimulate the kidneys to produce golf course vitriol, which will increase the absorption of calcium ions. And although these will stimulate osteoclast to remove calcium from bones. So within the same organ, we have one when portion that is increasing calcium levels in the plasma and another portion that decrease in calcium levels in the plasma, which is really neat out in one organ. We can have different glands. That are, that are antagonistic to each other, thereby trying to find that balance of circulating calcium levels. We've talked about the thymus gland before. We've talked about the lymphatic system. It's very active in young children and it will reset after puberty also to kind of stay the same size doesn't grow in 2D with us as we undergo pre-puberty as well as we've covered before it will produced by motion, by motion is just a cocktail of different types of hormones. And all these will cause the fight to undergo maturation and differentiate into teeth off. And so we're just have activation of, of our lymphocyte, activation of our T cells, the differentiation of T-cells. Here we have our adrenal glands. Remember our adrenal glands are associated with the kidney. And human. They sit right on top of the kidney and most other animals, they're sitting right here, right off of the descending aorta and the fear vena Cato. And so with this we have two main structural regent of the adrenal glands. When we look at a cross section here we have a cortex being the outer region, and then we have a medullary region or medulla and the center. Each of these produce different compounds and there's different controls allowing them, causing them to the leaf gives different woman. So here we have a cross section of the kidney. So here we have the cortex itself, and then we have the medulla. So within the cortex we have three main layers and they're all producing different things. When we're talking about control of the adrenal gland of the whole. Remember that the cortex is under control from hormones being secreted by the interior pituitary gland. While the medulla is under direct control, direct neural control from the hypothalamus itself, which is really neat. Seeing that, that distinction. And the joint and the Zona Rosa, we are producing aldosterone production. So this is a hormone that will reduce water loss and ion while loss. So this is a hormone that will increase blood pressure, increase blood volume in the zona lotta. This produces our stress hormones, cortisol, cortisone Court External. Yet again, reduce inflammation, cause glucose to be relieved. Things back. And then we have, are Zona particulars. So that was an interesting zone because this is the zone that produces androgen. So androgens, It is a family of hormones called the male sex hormones. The primary when being. So remember in females we have females produce testosterone, but they, they thermophilic testosterone to estrogen or Ester dial-up primarily. And so even and females are even in males, they have been castrated. We still have or neutered, which we're talking about a PET. We still have antigen production here in that zone I particularities. And so this allows for regulation of libido, hair growth, muscle growth as well in conjunction with growth hormone. And also this will stimulate blood cell formation to so we have so stimulation of the earth, the pollicis through, through the, through these androgens. And the Adrenal medulla. We have these two distinct chromite themself, and each one will produce epinephrine and norepinephrine. Remember that epinephrine, norepinephrine to the same thing. They used to be called adrenaline. Don't use adrenaline, that's an old antiquated term. It used to be called adrenalin because it was from the adrenal gland. Right? But the more correct term, the term that we use now, if epinephrine and norepinephrine, they're basically the same compounds, just epinephrine is more biologically active and it's secreted at higher concentration. So that's why we typically think of epinephrine itself. Okay, let's talk about organs that have secondary endocrine function. So let's talk about the kidney. So remember, her kidneys primarily the Netherlands themselves have the capacity to impact whole body blood pressure. And one way to do this is to the production of rent it. So when the men vine and what it will do is that will convert angiotensin urgent to angiotensin one. Then this angiotensin one travels through the bloodstream, Tillich goes into the lungs and then with angiotensin one is converted into angiotensin two. Now that angiotensin two, when it reaches the cortex of the adrenal gland, will release, we're really aldosterone, also on its own. Angiotensin two will also cause vasoconstriction. So if angiotensin two itself will cause vasoconstriction, which will increase blood pressure. But we'll also release aldosterone, which causes an increase and water and ion retention, which will also increase blood pressure as well. In addition to this, the kidneys also produce urethra pearl eaten. Remember that this is a peptide hormone and if stimulates your authors like production, okay, this stimulate the formation of red blood cells. All associated with this. We also have the trial, this is a steric hormone as well. This will increase calcium absorption by the intestines. And this was made by vitamin D. So this wire by having vitamin D within our body, we can make this helps to trial and increase our capacity to absorb calcium. Out of the heart itself also produces some, some hormones. These hormones, though, they typically only get produced when the, when the heart isn't doing so great when it's under a lot of stress. And so there's two types of hormones that are produced by the heart. We have atrial natriuretic peptide and we have brain natriuretic peptide. That's kind of a misnomer, but it, even though it's called Brain antibiotic peptide, is produced by the heart. And so what these two hormones will do, this one increases that is very large. So the brain, a terrific peptide. This increases and very large levels, right when the heart, one we're undergoing pop, cardiac arrest or cardiac, or heart like really doing poorly, we see very, very high levels of this hormone. Anyhow. Both of these will oppose the activity of angiotensin 280 h. So what this will do is that this will reduce blood pressure and blood volume atrial natriuretic peptide. This one, distance released fairly regularly. Yet again, it's a healthy heart that doesn't tend to, to generate a ton of it, but Some degree of cardiovascular disease. You'll be reduce, you'll be producing AMP typically. But when you're, when you see spike levels of BMP, that person's in trouble. Typically, not always, but typically the patent music. Let's talk about the pancreas. The pancreas is interesting because it has a duality to it, yet it has a very large role to play as an endocrine gland, but it also has a very large role to play as an exocrine glands that kind of fit between these two worlds. And so add an extra function. Remember, that produces a lot of digestive. The enzymes that produces bicarbonate, allowing for the buffering of the time coming from the stomach also produces a whole host of other digestive enzymes in a wide array of those. But as far as endocrine function through the pancreatic ellipse, we have a whole host of things that are produced. And within that it looks we have four major cell types, alpha-beta, delta NFL's. Let's take a look at the hormones of the pancreas. So here we have glucagon and insulin. These are antagonistic hormones. So glucagon from the alpha felt this caused that increase in blood glucose levels. This is due to stimulating the liver to break down glycogen. Whereas insulin from bathe itself, that increases the capacity of cells to absorb glucose, okay, which will therefore low work like glucose levels. When someone you're diabetic. If there are Type two diabetic, they have what's called insulin sensitivity where their body isn't it sensitivity the amount of insulin being produced versus if someone say type a, type one diabetic or what's referred to as juvenile diabetes. They produce either no implant or a very reduced amount of insulin. Here we also have somatostatin. Somatostatin from adult I felt this is a general, a hormone that is used in a variety of mechanisms of the body to, to stop things are slow things down in general. So this will inhibit glucagon and insulin production overall, but this will also slow food absorption rate as well. So it's basically just I, just putting the brakes are slowing down general processes within the body. Then here we also have pancreatic polypeptide that is from the F. So this one's interesting because it will inhibit gallbladder con, contractions. So the contraction a little gallbladder during, during digestion, but also this will regulate the production of pancreatic enzymes within the pancreas, the tough. So you have different cells within the famed Oregon regulating the functionality. Other cells which is printing. So let's talk about the testes. So the interstitial cells release testosterone. We've already talked about this before. So this promotes production spur if maintain the accessory secretory glands that produce all, all of the ********* that's produced. And also the influence of secondary sex characteristics, increased muscle mass, facial hair, things like that. And this will also stimulate muscle growth. Associated with this, with the nerve cells within the Tethys. These relief inhibin, and this inhibin will slow down the production of SPR. And so what it'll do is it will depress. A follicle stimulating hormone from the anterior pituitary gland. So here we have hormones produced all the way down and technical communicating with the brain. So this endocrine system and ecosystem as a whole can go both ways anywhere that we dump these hormones into the bloodstream as soon as they once they get to their intended fell type, they will impact the fault type assuming they bind to the receptor. And so with this, inhibin and FSH interact to maintain sperm production at normal levels. So yet again, they're antagonistic to each other. So when inhibited five, we don't have a lot of sperm production. When FSH is high, we have a lot of sperm production. And here we just have the ovaries for, for contract with LIGO sites. They can develop within follicle. Yet again, the follicles and oocytes mature due to Follicle Stimulating Hormone. The political yourself produce estrogens, mainly extra dial, and then yet again, def, mature eggs or ovulated due to luteinizing hormone. Yet we've already covered this in reproduction, but just kind of a refresher for all this. And then after ovulation that Paul could become the corpus luteal, which will then produce progesterone, preparing the body for the profitability of pregnancy. It felt. So with this progesterone we're calling into Rachel lining thickening, but we also cause the mammary tissue to start change in anticipation of pregnancy. The DWI drug menstrual cycle, why a woman's breasts can become tender due to these changes that are occurring. What the corpus looting will also produce is relaxing. And so this is more towards the end of pregnancy until what will relax. And we'll do this, we'll do some the pubic symphysis. This will also the lack the cervical muscle than the Cerveteri cervix itself and will stimulate mammary gland development. So yet again, this relax and have a variety of roles at, towards the end of pregnancy to get things ready for parturition. So the corpus luteal not only maintains pregnancy that sets the stage for, for childbirth, for, for parturition itself. And finally, let's talk about the pineal gland, the pineal body. This is part of the hypothalamus. This contains neurons, glial cells, and special secretory cells called Flight, which produce melatonin. Melatonin is a hormone. It slows things down. It gets us ready for sleep, ready for inactivity, and slow down our metabolism slows down production of sperm O site activity of reproductive organs. It helped that our circadian rhythms are daily rhythms of biology. And so what happens is that as we are exposed to reduced amounts like of like this in this hormone, melatonin will increase, increase in the circulation amounts, thereby getting the body ready for sleep, getting the body ready for sitting down for the day, at least comparable. So students when you're reviewing this chapter, Think about the distinct classes of hormones comparing or steroid to our amine versus our peptide, remembering that our steroid hormones are nonpolar, so they can easily diffuse into cells. No problem. Think about the distinct hormones that are being produced by, by different glands, their actions and Particular Think about the interactions between the hypothalamus and the anterior and posterior pituitary glands and how those are distinct from one another, right?

brain

It listens. In this chapter we're going to talk about the functional regions of the brains, will talk about the formation and the flow of cerebral spinal suits. And we'll also talk about cranial nerves. All right, let's get started so that the lump them letters between the brain and the spinal cord, both the integrate information, but both of them relay information, but Acre and efferent pathways, but the brain will integrate and profits both simple and complex information. While the spinal cord is mainly simple immediate responses that they use are things like they mainly somatic reflexes and fell when we're talking about the, the adaptable responses. These are a bit slower, relatively speaking, we're still talking about very, very fast responsive to stimuli or dealing with a reflex arc. But these adaptable respond to that a little bit slower, sometimes a little more complex, dealing with multiple systems. These are housed within the brain and handled by the brain at an Integration Center. One of the way the brain will elicit control of the body is through the 12 cranial nerves that emanate from the brain with if there's four general functional types of these cranial nerves. Some are just solely sensory, solely bringing information to the brain. Some are special sensory. The distinction between special sensory and sensory is that general senses. These are things like touch, pressure, vibration. Our special sensory or information. This comes from special something. So taste, sight, hearing, balanced things of that nature, which we'll cover a little bit later. And then we also have motor neuron leaving are nerves that are solely sending information orders from the brain. And then we have some nerves that are mixed, that have a duality that they bringing information to also send out orders. And so what we're gonna do in the first portion of this is we'll talk about the distinct regions of the brain in general, talk about their functionality is, and then get into some specifics about how the brain functions. Note you could teach an entire course on the brain. We're just really take a quick stab at it. So first let's talk about some generalized morphology of the brain itself, focusing on the two major regions, the cerebrum and the cerebellum. So on the surface of the cerebrum, we had the foci, which are shallow groove. Then we have these cheer i, which are rigid so that the bumps on the surface of the cerebrum, we have fissures which are deep groove. So an example of this being the longitudinal fissure that separates the cerebral hemispheres. We have. And the big distinction here is that we have the cerebellum and the cerebrum. Cerebellum. This is really about smoothing out somatic, somatic motor functions. And we'll also adjust output of somatic motor centers. So the, the cerebellum, one of its main function is to promote smooth motion. The reason we don't walk like robots move like robots because of the smoothing out of activity of that coordination between different somatic regions by the cerebellum, the cerebrum or telencephalon. This is where we have higher brain functions. Ok, so conscious thought prophecies, intellectual function to memory, language, math. That we also have conscious regulation, sculptor, muscle contractions. So anything that you do that acted that you're actively controlling, consciously controlling your somatic reflexes or sorry, consciously controlling your somatic system, your skeletal muscle, this emanating from the cerebrum itself or the cerebellum allows for smoothing of those profits. Whether it be through conscious activity or conscious control or through a somatic reflex arcs. So let's look at the center of the brain, the brain stem. This is the region of the brain that if there's any damage to it, it will most likely kill you. The issue with the cerebrum is that with the cerebrum, you can have damage to a large portion of the cerebrum, but still maintain like that wildlife functions. And so within, within our brain than we have distinct regions. So let's look at the docs Teflon first. So the diencephalon, what we have is we have our hypothalamus. This contains the pineal gland is used for rhythmicity to cycle, daily cycle than yearly cycle of the body of physiology. The thalamus, the thalamus that relay the information to the cerebrum and profit from its sensor information that's coming in. The thing to keep in mind, especially when we're dealing with portions of the of the brain stem, is that a lot of it is. A lot of these sections will receive information. Since receives sensory information, they'll do something with that sensory information, but then the relay that sensory information further up for more acute, finer refinement of that, of that information. So say we offend flight and N8 portion of the brain stem, but then we detect whether it is a kitten or a TI will make that distinction in the cerebrum itself. We can have a lot of sensory information, go to multiple regions of the brain. And then here we have the hypothalamus as well. This is hypothalamus, Swiss Army two of the brain. It has a ridiculous amount of thing that has a ridiculous amount of control over it. So it's evolve with emotions, thirst, some habitual activity. And also where secreted and amount of control over the body is connected to the pituitary gland via the infundibulum and if the feet of control of our endocrine system. So the hypothalamus not only an act, rapid control through the neural control, but it will also enact long-lasting chronic control via the endocrine system itself. So a massive amount of control. Looking at some of the other regions we have the medulla oblongata. So this will relay information to the thalamus at itself has certain centers that will regulate heart rate, blood pressure, and digestion. So you get again, being the brainstem, these region, if something were to happen to these regions, you would just keel over and die. Or these are the regions that really regulate your physiology, maintain a lot of homeostasis. Here we have the pons, we've talked about it before. Little bit will relate, relay information to share a bit to the cerebellum and the fellows regulate somatic and visceral motor center. So a lot of regulation of different body functions. And then we'd have them up on the midbrain. And this is where the proper thing, visual and auditory information. We maintain consciousness and alertness. And it also involved a lot of reflexive, somatic response to stimuli. It flipped method TEFL on the mid-brain with where we have somebody who say has Parkinson's or Alzheimer's where the damage in the center and that's where we see damaging response, general responsiveness and also fluid motion. And that results will receive things like difficulty swallowing and speaking that gets manifested from advanced Parkinson's or Alzheimer's as well. Let's look at a cross section of the brain. Some of this language is a holdover from when we talked about the nervous system as a whole and also when we talked about the spinal cord as well and fill with it. We have our cortex, which is in the cerebrum, cerebellum. This is superficial gray matter. And then we have nuclei which are clusters of grey matter made of spherical, oval, or we go into rural body, these nuclei can typically not be seen with the naked eye. These are seeing the staining techniques. So as we show off, a lot of these images showing up these different nuclei within different regions of the brain. These are shown off by staining techniques. You can't just open up a brain and clearly you can see some of them due to some bulges that they generate in the brain or some specific kind of morphology, gross morphology attached with that. A lot of these are highlighted through advanced staining techniques that we are difficult to see and an unstained brain. Alright, so here we've got the Cortex running along. And yet again throughout we have do these distinct clusters of grey matter nuclei. As it's seen in lab, the brain is not a single solid math is a whole host of spaces within the brain. And these spaces are filled with cerebral spinal fluid effect. These are the spaces were cerebral spinal fluid is first produced. And so the cerebral spinal fluid has a whole host of functions. It rot of exchange within the central nervous system as a whole. And it also provides a degree of cushioning for central nervous system. It allows you to kind of float in that, in faith. And within the brain prop, we have four fluid-filled that tools. And we'll get into closer in the neck flight. But here we can see their general shadow outline and a whole brain. So looking a little closer at the ventricles themselves, we have for them yet again. So our first second are a lateral ventricles. These kind of looked like something out of halo or something like that. They almost looked like some kind of sci-fi weapon. Then we have our diencephalon. And then we have a fourth ventricle, which is between the pons and the cerebral. So here we can see our fourth ventricle. And then there's a third ventricle kind of connecting the two, where we see a junction of the two lateral ventricles. And the lateral ventricles. These are located within each cerebral hemisphere and these are separated by the septum pellucidum. So looking a little closer at some of these other ventricles. So looking at ventricles 12, the lateral ventricles, these the main portion of these are on the parietal lobes. The anterior horn extend into the frontal lobe, the posterior horn extends into the occipital lobe. So yet again, we're maximizing the degree of surface area that's exposed to the cerebral spinal fluid. And as we're generating the cerebral spinal fluid, if these regions of the brain that get first dibs at exchanging with different material. We had the inferior horn then this looping downwards extending into the temporal lobe. And in these first, these two, these two lateral ventricles will connect to the third ventricle via the interventricular foramen. We can see right there. So we have third ventricle, which drains the two lateral ventricles. And this connects to the fourth ventricle via the cerebral aqueduct right there. And in the fourth ventricle itself, this will connect through to the central canal of the spinal cord. So that material, that cerebral spinal fluid then drained through. So that central canal, that hole that we saw in the cross-section of the spinal cord. This is a continuation of that fourth ventricle. Now note throughout the ventricles, throughout the entire system. There's a whole host of foramen that will allow the cerebral spinal fluid to leave the centralized, the central spaces. And circulate around the brain and also circulate throughout the rest of this, of the central nervous system itself. And so these, these connected sub arachnoid space of the brain and the spinal cord to allow for material to flow over. So we have production of cerebral spinal fluid within the brain, and then we have a whole bunch of foramen that allow to leach out and then circle the outer portions of the brain but still retained within the menagerie. And that's the important thing to remember or talking about. The central nervous system is that it's all contained within that dura mater that dramatically in the outermost portion, everything in the brain, just like all other nervous tissues, fairly fragile, so we need to be able to protect it from the internal portions of the body and from the outside world until we protected through the bones of the skull so to the parietal frontal occipital temporal bones, making the bulk of the brain case. We have a cranial manages which you saw with the spinal cord, the dura mater forming that very tough exterior shell casing around the brain. And we also have the arachnoid mater and the pia mater also supporting the weight of the brain itself. We also have cerebral spinal fluid. Cerebral spinal fluid. So the brain can basically passively float within this back the fluid and that allow that to be supported by this fluid. We also have a blood-brain barrier, which we'll talk about a little bit more. This limit change of material highly regulate the exchange of material with the blood supply. So it makes it more difficult for pathogens to reach the brain. It makes it, but at the same time, while it's harder for pathogens to reach the brain, it's harder for certain molecules to reach the brain. So whenever you read a study that says, Oh, this molecule will increase brain function, does that molecule really make it clear to the brain or in that study that they just inject it into the brain, the racks or into the brains of people. You have to think about that because the blood-brain barrier protects the brain, but unfortunately also greatly restricts what can enter that cerebral spinal fluid. And we also have a very rich much subplot which the brain itself can exchange material with the Latour that runs through it. But yet again, it's all very highly regulated by those glial cells. So we don't have just free float, free wheeling and dealing of much of exchanging materials. It's highly regulated and it typically blood, cerebral, spinal fluid than brain tissue. Alright, so let's talk about the meninges themselves. So let's first talk about the dura mater, this being the most superficial layer. There are tough fibers. Exterior portion. It is bound to or intimately associated with the bones of the skull kth felt. And so we have the pair osteo cranial dura and this outermost layer of the dura mater. This is fused with the periosteum of the cranial bones. And so keep this dura mater in place. And then we have, I'm an NGO, Craig Eudora, the innermost layer of the dura mater itself. And within the flooding layers, very important because within the player, we have these massive vena, Finer Foods that are present and these very large veins. Remember whenever we talk about finite strain into these large veins are draining material away from the brain. They're draining the cerebral spinal fluid. So a lot of time, faith, somebody had an injury and they're building up pressure, cerebral spinal fluid pressure within the brain. Typically one way that we can. Generate increased pressure within the brain kick if something happened to the finite that they get blocked if something happens. And so we have to build up the pressure because we constantly are draining a normal scenarios will constantly draining away the cerebral spinal fluid via these large dural sinuses that run along the brain, which we'll talk about that more in a little bit. So when we're dealing with support of the brain, we also have these extensions of the dura mater that lead, that basically kind of encase the brain in, in connective tissue as well. And so we have a whole bunch of third belie or cerebral, right? That gives structural support to the branch. So we have the tentorium cerebral. So the separate with cerebellar hemispheres from USSR and took the sheet of material right here separates the cerebrum from the cerebellum, the fog February. So this separates the cerebral hemispheres. And so we can see this kind of running along right here, running along that longitudinal fissure. And then of, of important note here we have the diaphragm fill line and this line filtered Tercek of the sphenoid bone. This in case of the pituitary gland, this is very important because one of the things that allowed the pituitary gland to bypass the blood-brain barrier. There's a couple of readings of the brain where we don't have a fully developed blood-brain barrier. And these are important because these are places where either the brain is, I think blood supply and or portions of the brain are dumping stuff into the blood supply. Vasculature and with the pituitary gland up dirtier gland is dumping massive amount of stuff into vasculature, which is super important. And so these different extensions of the dura mater, the aid in supporting the brain in place to support it. And look at all the structure. We have side-to-side support. Here we have where the entire weight mass with the cerebrum does not crush. And in addition to this, these membranes also allow for the presence of finite that looked at all the planets running through, through this connective tissue. Yet again, creating that cerebral spinal fluid because allowing material to leave that cerebral spinal fluid, allowing new thrill spinal fluid to be pretty because we're constantly producing cerebral spinal fluid. We're constantly draining it as well. So let's look at our arachnoid mater. Remember that our arachnoid mater is intermediate between the dura mater and our PM matter. And so as we look right here, we can see the pia mater right up against the brain itself. And we have the arachnoid mater scattered throughout between the pia mater and the dura mater thought. So within the arachnoid matter, we have these structures called arachnoid regulations. These are really important because neither Spock with, in the arachnoid mater, where cerebral spinal fluid will flow into that, into those sinuses, will flow into the venous circulation. So it's through these erected regulations that are found throughout the arachnoid mater that allow that cerebral spinal fluid flow. Remember when we're dealing with it's arachnoid mater and the arachnoid trabeculae. Subarachnoid space developed by that established by the arachnoid mater. It, cerebral spinal fluid flows through this region of flow into this entire region. The arachnoid mater important. Remember, arachnoid. Well, it looks like cobweb it that via the profit for the dealer structures that directly matter. They don't look like they're super tough, but generate an entire mesh, keeping the brain in a neutral position so that we can allow cerebral spinal fluid to travel around completely so that the brain isn't squished up against one portion of the dura mater, not allowing cerebral spinal fluid to flow around it. Okay. That the selected matter allow there to be space, kind of to some degree, suspend the brain and placed passively so that Lincoln had this cerebral spinal fluid travelling around a prevalent through it. And yet again, that cerebral spinal fluid travels through that subarachnoid space. This is where, where we have that arachnoid mater it felt emanating. These are IRAC, the trabeculae. And so the trabeculae basically think of it as a spider webbing hit felt, were cerebral spinal fluid can travel through. And this is where cerebral spinal fluid is found. And finally, we have the pia mater, the inner most of the money that was intimately associated with the brain and it is attached the prophecy of the astrocytes that anchor it in place. And it's in the pia mater where we see vasculature intimately associated with the brake. This will also follow the sulci and gyri of the brain as well. So and larger blood vessels are also anchored. But via the pia mater also. Lets talk about this blood brain barrier. This is primarily due to Astrocytes. Remember, we can have exchange of material through the astrocytes directly with vasculature, but it's still highly regulated by the astrocytes. Typically we see blood, cerebral spinal fluid than brain tissue, but we can have blood than to brain tissue, but through brokered completely through these astrocytes, the bare minimum, we only have the astrocyte closely guarding what can enter the brain and what can leave the brain. Ok. And so yet again, these blood vessels within the endothelial lining of the vasculature that reaches the brain at highly, highly interconnected type junctions and limiting what could come in and out. As we've seen before, lipid soluble material can easily come in and out. Because of its chemistry, these nonpolar substances can just come in and out of cells willy-nilly. And it's no different if all water soluble material that can only transfer through the endothelial cells of these capillaries and through the astrocytes. The very particular transport mechanisms, note, along with the lipid soluble materials, gases can freely come in and out as well. Remember that the brain at the very, very hungry, too, metabolic reactive. So it needs a lot of oxygen, eat a lot of carbon dioxide, and it needs a lot of energy to function. And so while this profit is very selective, it still allows a large amount of material to come in and out of the brain. There are four main places where the blood-brain barrier is very different from the hypothalamus. Because the hypothalamus affect the composition of the blood and a variety of ways. It even accept that the temperature blood capillaries in the pineal gland that, that do not follow this law. The capillaries within the choroid plexus, the capillaries in the choroid plexus, these important together where we're producing cerebral spinal fluid and as light. While a different mechanism of allowing things in and out. And then we have the capillaries within the posterior lobe of the pituitary gland that have a massive amount of dumping of product into vasculature. So let's look a little closer at cerebral spinal fluid itself. So that CSF has a whole variety of roles. It aids in an buffering the brain to aid in providing cushions support. So it protects the generalized neural tissue from surrounding bone along with the meninges. It provide support to the brain. The brain can passively float in this pool, the fluid surrounding it. The main network for transporting nutrients. It will also transport waste away from the central as well. And so remember, the central nervous system is very metabolically active. So it's constantly producing CO2, constantly taking, taking up nutrients, conflict producing metabolic waste products. So the CFF is a very fast way to move the stuff around. And yes, we have exchange with vasculature. But by just taking it through the CFF and at the FF, FF constantly the drain is a very fast way, especially getting rid of waste points where we have formation. Cerebral spinal fluid itself. This is produced by the epidemics of the choroid plexus. So yet again, we're not undergoing direct control by the astrocytes. The epidemic felt that are interacting with vasculature to make the cerebral spinal fluid thought and epididymal thoughts which will act on the transport nutrients, vitamins, and ions into the CFF. Yet again, gases can tactically transfer through nonpolar substances with lipid molecules can path. It can transfer through perfectly, no problem. And these epidemics not only will produce cerebral spinal fluid, but they'll also pull stuff out of it as the encounter waste products as well, and dump that into the vasculature, dumped into those capillary beds there to width. Let's talk about the production and circulation of cerebral spinal fluid itself. Cerebral spinal fluid is formed in the choroid plexus. We have multiple court plexuses. Throughout, throughout the brain. We have some, and the lateral ventricles, we have it in the third ventricle and in the fourth ventricle. And so at the flights we are producing, producing cerebral spinal fluid, but we're also suffering its contents and regulating its well. And eventually all cerebral spinal fluid will enter venous return through those miraculous granulation switch string into those big sinuses. And so as this cerebral spinal fluid is formed within the, within the ventricles, it will then leave to the, the suit of the central nervous system as a whole. And so with this, it anxious subarachnoid space through a variety of different foramen. And this frame and the lateral aperture and the median aperture that allow for, for this material to leave and start circulation and also travel through the central canal. And yet again, it will drain through those arachnoid granulation into the dural sinuses. So here we can see now reckoner granulation with the straighten out. And here we can see the whole host of, of apertures. Here's a median aperture allowing that stuff to leave, to leak out into the rest. And two, that subarachnoid space so it can bathe and show around the brain. Give support to the brain. And the brain kind of basically flips in the liquid. But we do have a very large amount of material exchange in the brain between the cerebral spinal fluid and vasculature. We also have direct interaction with fastly trip to the brain via the astrocytes, the astrocyte wrap all the capillaries within the central nervous system and they will regulate what's happened, okay? And towards healing what the bringing tough as far as our til supply, mainly through the internal carotid artery and the vertebral arteries. And then for drainage of the brain as a whole, this is mainly through the internal jugular veins. So now let's highlight different regions of the brain and the functionalities will start inferior worker superiorly. And we'll start with the brainstem at the hole. Remember when we're dealing with a bring them. This is the region that will attach to the spinal cord tough. In particular, the medulla oblongata being, being the most inferior portion of the brainstem that is directly connected to the spinal cord. So a ton of information passes through the medulla oblongata up. Remember that the spinal cord, yet that can act as an integration center for mainly thematically Flex. If a narrative conduit of information leaving and coming to the break. Everything that it's not handled by the cranial nerves that we'll cover it a little later. If handled through the information and orders that are traveling through the spinal cord, those effect an efferent pathway information. And so when we're looking at that medulla oblongata yet again, it is the gateway for information that's traveling through the spinal cord from the brain as a whole. We have a whole host of nuclei within the medulla oblongata that are responsible for a whole host of functionalities. Remember, with these distinct nuclei, the reason we know they exist is due to a variety of staining technique. We can kind of roughly F0 them. Sometimes. In some cases we can kind of dissect them out for super careful, but they've readily theme that distinctive staining techniques. With this, we have a lot of cranial nerves that are also connected to the medulla oblongata as well. And we have a whole host of autonomic control centers that are also up there, found within the medulla oblongata as well. And so yet again to the importance of the brainstem, where you can have a lot of damage, a massive amount of damage occur to the cerebrum. It even in some cases, bellow. But if you have damage to the brain, and particularly if you have damage to the medulla oblongata dog. And you cannot, you can no longer maintain homeostasis. And when we're looking at the different nuclei, we will highlight all of them. But one of note is the Psalter nucleus. And this will receive a lot of visual information, spinal and cranial nerves as they come through. And so the nodes we can see here on a, on a frontal view of, of the medulla oblongata. We have a whole host of even cranial nerves emanating from it as well. So if this major, major hub of information leaving and coming from the brain, traveling through the cranial nerves, but also the spinal cord as well. So looking a little closer at some of these nuclei that are found within the medulla oblongata, We have the graphs, I'll nucleases that Punic nucleus it again, passion somatic information to the thalamus, to body position, body orientation and that orientation. In this, we also have the olivary nuclei which generate the march bulges. And then these are dissenters for, for relaying information that from the cerebrum, spinal cord, diencephalon, and brain stem to the cerebellum. And so that in this region here we also have at the start of a connection point to the cerebellum itself. So we have a lot of interconnection or cross talk between these different regions of the brain, also occurring at the medulla oblongata as well. And here we can see a whole host of different centers, cardiovascular centers with respiratory rhythmicity centers, et cetera. So continue to talk about the medulla oblongata. We have a whole host of cranial nerves that are attached to it that emanate from it. So we have a whole host of sensory and motor nuclei from these cranial nerves. Silly had the vestibulocochlear beg if accessory and hypoglossal nerves emanating to and from the medulla oblongata. And within the medulla oblongata We have a very distinct reflex centers. So we have our cardiovascular centers or cardiac and vasomotor, cardiac control and information from the heart it felt vasomotor assessing and controlling constriction or dilation of the vasculature. And we also have the respiratory rhythmicity Center. Its nucleus, both dorsal and ventral, found within the hypothalamus, within the Pong that sits on top of the hypothalamus, we have rationalistic in pneumo tactic respiratory centers. So if there is small region here, we have control, the heart, controlled love, and this is layer, extreme damage. The centers you die because you can't breathe and heart can't pump due to die. As we packed up through the mesencephalon, the midbrain itself. We can see a lot of structures because the cerebellum has been removed, it would normally be attached through the cerebral peduncles as well. So we'll cover that later. Here we can see the Ka'apor credit Gemini. And with it we can see the superior colliculi and inferior colliculi. And so what the fees are on the surface of the mesencephalon and deeds will process the initial processing of auditory visual stimuli with inferior colliculi, adequate proper thing with superior colliculi, visual processing. So this is where it is first accessed. Information will go into other centers of the brain. So just because we hear something, this just let us know that we heard something. Further processing occurs within the cerebrum where we know that that's a horn versus Beethoven symphony. We can prophesy different things where we can see, oh, that's a kitten versus a rabid squirrel. What-have-you. We know that we're seeing something but, but interpreting that image and trumpeting that sensory information occurs elsewhere. This is just what's first Prof. entire parcel to be sent upwards. And so width is within the walls and floor of these nuclei. We have, we're looking at a cross section of this. We have a different nuclei found here. So we have the red nucleus and substantia nigra. These are two structures than a person who has Parkinson's or Alzheimer's starts degrade and mislead. The hope was to pathologist caused by those conditions. So these regions are involved in maintaining alertness, muscle path of muscle tone and limb position. And so this is called the causes that hand trembling and general kind of shaking that we see in Parkinson's and lack of awareness that we also see an old famers as well. With our ventral lateral surfaces. We have the cerebral peduncles, and this is where we have attachment. Cerebellum. So we have these kind of fide wings to it where the cerebellum gets attached. Also note that we can see here clearly, we can see the core plexus of the fourth ventricle. We can also see the choroid plexus right here as well, along with the third ventricle. So kind of looking at a cross section that's written with imaging techniques, we can see the substantia nigra, they can see the red nucleus. It does kind of look like one of those cheap ice cream treaty you get from like a supermarket or something like that. That's supposed to be some character. Anyhow it needs region here that somebody has Parkinson's or Alzheimer's. They will degrade and reduce motor function, reduce alert message, et cetera. So here we're looking at the diencephalon, which is the third law, control for the body. Within this region we have the hypothalamus, this produces melatonin, which regulate day and night cycles of body function. We have the thalamus, which has a whole variety of functions, which we'll get to it a little bit. And the left and right halves are connected via that into thermal adhesion. And then we have the hypothalamus felt that extends from air superior to the optic to the mammillary bodies at the space in between those two structures. And extending from the hypothalamus is the infundibulum, which connects to the pituitary gland, allowing it to communicate and control the pituitary gland and a whole variety of different waves. And here we can see some of that, some of the structures, the thalamus itself forms, the walls of the third ventricle. Inside of the brain has its own thalamic nuclei, which is egg shaped. And as we see here is just one single thalamic nuclei. And with it we have a whole host of different structures that control a whole variety of different things. Until we have the anterior nuclei as part of the limbic system. The limbic system is where we had the integration of emotion and physiology. So that's where your emotion can, can, can impact your heartbeat, for example. Of medium nuclei for this relays information to the frontal lobe. We have the ventral nuclei relaying information, the parietal lobes, we had the Pasteur nuclei. This relays information to the occipital lobe, but also relate auditory and visual information as well. We have then a nuclei which will interact with the cingulate gyrus and the parietal lobe. Yet again, having some little to play with the limbic system as well. So when we're looking at a center of control, you really don't get much bigger than the hypothalamus. The hypothalamus that there's one spot in the brain that were to be destroyed and you basically drop dead immediately. It would be the hypothalamus. It's ridiculously important have subconscious control skeletal muscle. So a whole host of somatic reflexes are controlled by the hypothalamus. It will control the heart rate, blood pressure, respiration, and digestive function, thereby impacting other regions of the brain which will then elicit control as well. It secrete a whole host of indirectly or directly, secretes hormones directly itself, will secrete two hormones. It will secrete antidiuretic hormone, Rij, super optic no cliff and an oxytocin via the periventricular nuclei. Both of these hormones are produced by the hypothalamus because it had basically neurons that stretched from the hypo Matt hypothalamus to the infundibulum, to the posterior pituitary gland. And near that, it exerts control because it directly secrete these compounds into the bloodstream. Has control of the anterior pituitary gland, the production of hormones. Within the hypothalamus. We also have emotional behavioral drives. Also, thirst dry. So what caused us to want to seek out water, to drink water also seek out food with a high water content as well. We have a lot of coordination between voluntary and autonomic functions. And so with this, we're seeing how autonomic function can allow for certain voluntary function. So save as you speed up walking or slowdown logging, what keeps you from just tipping over. So we have the integration of the natural rhythmicity centers within the body and then within the hypothalamus, it smooth over the transition between conscious. Let's certain systems and, and in unconscious control systems, especially when we're dealing with somatic reflexes, when we're dealing with movement. In general. With this hypothalamus who also controlling or assessing body temperature via the preoptic area. So our body temperature is controlled by the hypothalamus. So when we set to start a fever response, it's the hypothalamus that will start this as well. And it will also impact circadian rhythms via the super charismatic nucleus, impacting communicating with the pineal gland stuff with if also within the hypothalamus we have reflex arch that deal with swallowing, licking, and feeding reflects especially one for example. And this is via the mammillary bodies that communicate with the hypothalamus. And here we can see the hypothalamus novels glory yet again at a small segment, but it's super PAC with distinct region to have a whole host of different functionalities. And let's talk about the cerebellum. The cerebellum, just like the cerebrum, has two hemispheres. With if. Just like the cerebrum, cerebellum has little folds on top of it. So these are the fully 30 like that are found on the surface and increase the available surface area that are similar to the gyri of the cerebrum. We have anterior and posterior lobe separated by primary fish IP. And we have the dermis, which is a narrow band cortex which separates both hemispheres from each other. Now sparse functional areas of the cerebellum. We have the flux, no jeweler lobes, the flocculent login or nodes. These will balance eye movements. That thing for smooth movement of the eye as we're tracking objects that have been moved to a field of vision. We have a lot of proprioception and balance, control here within the cerebellum as well. And we also have refining of skeletal muscle movements. And so with this, we have a smoothness of motion. Also the cerebellum have large role to play and learn reflects that aids in establishing reflex arc that we're working with. Burglary flexors to enable their functionality so they establish muscle tone to allow for certain activities to occur passively involved through coordination by the cerebellum. It's what smooth out our walking if somebody has a damaged cerebellum, first and foremost, you see that they have either difficulty maintaining their balance. They had had difficulty tracking an object with their eyes okay. That it would be charred and kind of jerky as their eyes move. So if you moved a finger in front of somebody's face that their eyes were jerky. They may be, they may have some damage to their cerebellum. And also looking at the general ambush movement as well. If they're moat. Emotion is robot-like. There may be some damage or something going on with their cerebellum is. So here we have a cross-section of the cerebellum itself. So here we're seeing the cerebral cortex and nuclei and in general, the aid and subconscious coordination of movements, okay? Dealing, bringing in information about proprioception of body length position, but also the position of the body, of the whole balance. We can clearly and smoothly move skeletal muscle. We've got are the arbor detailed Tree of Life, which connects the cerebral cortex with the cerebral peduncles. And each peduncle allow for distinct range a connectivity with the rest of the brain, in particular, the brainstem. So we have the superior peduncle connect the cerebellum that the mesencephalon **** left London cerebrum. Or we have the middle, middle peduncle which connects cerebellum but the palm. And then we have the inferior peduncle connecting the cerebellum with Madu, long gone up. So let's look at the cerebrum now, which is the bulk of the brain. And this is where we're having a lot of conscious control of the body, especially if our somatic reflexes, we have a lot of interpretation offensive. And this is where we mainly interpret the information coming from the special such themselves. We also house memory, thought, personality as well through here. So we have two hemispheres separated by longitudinal fissure with the lobes. We have a frontal lobe, which is we mainly have conscious control of skeletal muscles allowing us to, to play video games, play basketball, shake hands, what have you? With our occipital lobe, we have perception of visual, visual stimuli. So this is where we can determine if that's a house tabular rabid squirrel, monkey out. Looking at the parietal lobe, this is where we have conscious perception of a lot of the general senses. So remember, we have not only undergrad interpretation of special licenses on the brink, the lists of interpretation of general expenses. So touch, pressure, vibration of pain, temperature, and tastes get Certainly there was quite a lobes. Well, with the temporal lobe, we have perception of auditory olfactory stimuli. And then deep to that is the in the lot itself that region. And with that, we have it and these centers are fairly close to memory as well. So this is why we have, when we smell certain things who brings a certain memories. So this is also where we can store the recollection of certain smells, but also we can interpret those smells as well, and we can also interpret auditory, auditory information. There's a distinction between hearing found and interpreting what those down to mean. Is that a bus or a current assuming cry, they know that sort of thing. And so when we look at the higher order functions of the brain, these are performed by the cerebral cortex. And this involves communication of cerebral cortex and other areas of the brain. This involves conscious and unconscious information processing. Unbiased functions are somewhat fluid and these can be, can be programmed to modifications and adjustments depending upon ontogeny. So safe, one region of the brain gets damaged or something like that. You can sometimes have cross-wiring that still enables certain functions, but you may lose others with that occurred. So when we're looking at functionalities of the cerebral cortex, we have lot of complex integration of sensory stimuli. Also output of motor responses to cause things to happen. There are a whole host of interpretive areas within the cerebrum. We're going to only highlight a couple here, and so the're just sum of note. So here we have Broca's area right there, that speech centre. So this aid and controlling breathing patterns for speech. So as we form different words, speak different languages, we have and you have to control his breathing patterns to make those sounds. Here were the prefrontal cortex. So this is where we predict consequences of actions. We can think about what will happen if some thing happens if we, if we feel that candy, but what can happen was run that red light. What is the profitability of happening if we do that? And Wernicke's area, this is where we have language comprehension and also analysis. So note that the ability to speak a language and the ability to understand language arts separate areas. Also, we have an analytical areas. Well, within Wernicke's area, we have the receptors speech area. And this is where we modulate volume. So as we can hear the resonance occurring in our head as we speak, we can modulate our volume accordingly. And then with the frontal eye fields we can, it is eight and coordinating eye movements as well. Typically conscious eye movement, but it can also have a role in unconscious tracking of objects as they move within our field of vision. So we're comparing our left versus right hemispheres. And you'll hear people saying, well, I'm left-brained or right-brained, whatever we have both or you, you, you, you'd be dead. In the left hemisphere, what we typically see are speech centers, writing centers, language, and mathematics. The right hemisphere primarily analysis by touch and part with this spatial visualization. So being able to assess volumes and spaces without directly measuring them and having that, you know, really knowing if that catches gotta fit in that spot or not Paypal thing. When we're looking at the different integration centers, we have communication between throughout the cerebrum, but also between right and left hemispheres of the cerebrum as well. And so with this we have our association fibers. And these association fibers or crack that allow movement of information within the three grim itself. So with this, we have our arcuate fibers and longitudinal finished and we have our Cummins, you'll fibers. And these can connect between hemispheres. So the Anterior Commissure and the corpus close in. We have a projection fibers. So the link the cerebrum with other regions of the brain and the spinal cord. So the midbrain and the cerebellum. And then we have our internal capsule, which are distracted Ethernet and eight Ethernet efferent fibers within the brain because we're also debris Not only will and information to the body as a whole, but it will also send information orders to different regions of the brain to, to allow things to basically kind of delegation of certain activities. So let's look at some other regions of control within the cerebrum itself. So we have the basal nuclei. These are matters of great matter embedded within the white matter and fear to the ventricles. The aid an automatic adjustment of voluntary motor commands so that a1 fake, if we want to wave our hands from there, that provides increased stability of the torso to deal with that generation of force, things like that, that allows for voluntary muscle movement. Torque curve. We have the caudate nucleus, the putamen. These are cycles of arm and leg movement during walking. Note that these are also impact can be impacted as well and somebody will have Alzheimer's or Parkinson's. But the globus molecular. And so with this, I just muscle tone and preparation for custom conscious moment, just like the basal nuclei. So at defining of a region of the body to allow for that, for that function to occur, that motion to a curve. And we have the colostrum. And with this we have a yet again automatic processing of visual information as well. So the pocket with the limbic system, the limbic system is located between the three of them, the diencephalon, and it's superior to corpus close them. This is an interesting area of associated structures because establish emotional state, width if these will also linked conscious functions with an unconscious automatic autonomic functions. So behavior, anticipation of certain things, of that sort of thing. And this will also facilitate memory storage and retrieval with, within this region, we also have the interaction of behavioral state with physiology where if you're anxious, it will cause an upset stomach or will cause heart rate to increase things of that nature as well. And so when we're looking at portions of the limbic system and the limbic lobe, the cingulate gyrus within **** gyrus, hippocampus, gyrus, hippocampus, a very large amount of tissue that deals with the emotional state and because of it, nearby association with a whole host of control centers of the brain. We can impact that directly, impact a lot of physiological functions with mood. And so when we're looking at the foreigners, felt this is attractive white matter connecting hippocampus with the hypothalamus and with a lot of these fornix fibers extend to the mammillary bodies and get again looking at memory by these will control reflex movements associated with eating. So swallowing is impacted or controlled by, in part controlled by these mammillary bodies. Other nuclei within that region that kind of play with the limbic system as well. We have the anterior nucleus. So this has picked this row information from the hypothalamus and the singular gyrus. And also within the reticular formation, there's alertness and excitement. And yet again to another region that due to all famers of Parkinson's can become damaged as well. So this is another view of the limbic system. The reason why it's so important is that it close proximity to these very large centers of control from the brain. And the centers communicate with one another and his wear, mood, emotional state can impact as Yahoo, they can't our control them, but they can impact. So here we have the cranial nerves. With the cranial nerves, which was the direct connection with the brain to the peripheral nervous system. All the other connections of the brain to the peripheral nervous system are the spinal cord, which is also a portion of the central nervous system, the tough. So this is where the brain can directly impact control or gain information and organize information. And so with this, when we talk about the cranial nerves, it's important to know their names because the names will aid you in remembering what they're doing. You know, learning nerve number two doesn't mean anything. But if you learn optic nerve, Oh, okay. Optic vision. Okay, that's visual. Alright. The agenda is a part of the peripheral nervous system. Many of these, most of these travel outside the vertebral foramen, so they don't even travel through the vertebrae themselves, let's say the vagus nerve, for example, the bulk of the travelers just within the body cavity itself, perhaps that can abdominal cavity. Some do use the vertebral foramen a little bit, but not a ton. When we're looking at them, they fall under one of four different categories. So we have sense, general sensory, just bringing information to the brain as a whole. We have special sensory, These are attached to special sensory organ, silk, typed, taste, hearing, et cetera. We have motor yet again, sending information from the brain to sending signals to have something happen these vectors to. And it happened to control different parts of the body. And then we have mix, some of these nerves have a variety of functions. When we're thinking about these cranial nerves, think about what they're attached to and what they're doing. And that's really what I'm holding you responsible for forties. So first and foremost, we have the olfactory nerves, okay, these, their function is to provide sensory information, specialised fruits or information to the brain. Our sense of smell. They originate in the olfactory epithelium that sending information to the brain. And yet again, they only pass through the frame of the cribriform plate and then they enervate with the olfactory bulb self as a whole. Now we have the optic nerves, okay? With these fend, specialized sensory information to the brain, the origin at the retina. So they're point of, of innervation to the optic disc, leaving the, each eye as a whole. And then yet again, the optic nerves cross at the optic chiasm, which will then continue along the optic tract themselves. Here we have the oculomotor nerves. So dv will control most, but not all of the extra ocular muscles. Okay. They do not control, does not control the superior oblique or the lateral rectus. That will also control the fiddler muscles so that aid in and allowing for accommodation to occur origin within an epsilon. And then yet again, these have autonomic fibers synapse in the ciliary ganglion to allow for, for control of accommodation itself. But yet again, the oculomotor nerves, most eye muscles, but not all. And these will control the ciliary muscles allowing for accommodation. The trochlear nerves, trochlear nerves will, oh, the only thing that this nerve does is control the superior oblique muscle. Only thing it does and its origin in the mesencephalon. Ok, so this trophy on earth, the only thing it does is control the superior oblique muscle. And here we have the abducens nerve, which all it does is control the lateral rectus muscle so that all it took to control that so voluntary muscle and it emanates from the poem's. Let's look at the trigeminal nerve. The trigeminal nerve has a whole variety of functions mixed. So we have an ophthalmic division, we have the maxillary division and we have a mandibular division. Okay. The ophthalmic division, different substrates to the sensations of the forehead I like to nose. Maxillary division is also sensory coefficients, the lower eyelid, upper cheek, and that we have a mandibular division. So this agent controlling mastication distance mixed, but it will also relate information on it from the side independent, factor them out through this trigeminal nerve that we sent in cooling. So the kept faith and, and spicy foods is detected. Information sent to the brain via the nerve, also the menthol in, in, in peppermint experiment, et cetera, is sensed by this, by this nerve as well. The origin of each division vary. Silica ophthalmic division from the o orbital structures, nasal cavity, forehead and ship your eyelid or maxillary division. And if your eyelid up all that done, teeth palate, part, part of the pharynx. So yet again, something by pressure to some degree. And then with the mandibular division, sufficiently lower gum, teeth, palate, tongue, salivary gland, and motor nuclei, the pump. So yet again, we have a, we have a mixture, the sensory and motor with the mandibular division of the trigeminal nerve. Let's look at our facial nerves. These mixed function. So for sensor side of things, these are generalized sensation, touch, temperature on the faith, but these will also relate. Take the information from the tongue. Two-thirds of the taste buds are innervated by the facial nerve. As far as the motor side of things, these will control the muscles of the face. So, for example, and cases where somebody has a stroke, you will see somewhat some paralysis of the faith. They will also with that dues, a large, large portion that they've spent that paste because that facial nerve becomes imperative, functionality will lose that ability to send information out that information. And yet again, it's origin depend for censoring the taste buds for motor relays from the pumps. So within the vestibular nerve, these function in sensory capacity, bringing information from the middle gear and the temporal bone, bones and to width if the sentence relay information for balance and hearing. We have receptors in the vestibule and the cochlea. And so with this we have, are the vestibular nerve that will go travel either distributed nuclei of the medulla oblongata and the cochlear nerve, which these Wilson cochlear nuclei, the medulla oblongata, vestibular nerve for ballot acceleration, velocity, cochlear nerve for hearing. So here we have the glossopharyngeal nerves. So this was a very, very mixed nerve. So this does generalized sense, special licenses and also motor functions as well. And so the posterior third of the tongue, that information that's gathered from that region is trapped, travels via the glossopharyngeal nerve or bitter and sour flavors. We have innervation of the carotid body. So effing, gaffe and kitsch fencing in the arteries. This half of the depth information is trapped, travels to the glossopharyngeal nerves. On the motor function side of things, over swaddling muscles are controlled by the nerve and our salivary glands. Salivary glands are controlled by this nerve as well. And so for origins, and if it's specialized sensory, These will be in the posterior third of the tongue. Those that are associated with carotid bodies will start at the carotid artery itself. And then we have those that are, that emanate from the medulla. Oh my god. A traveling to the salivary gland and somewhat of swelling muscles for motor function. Defense your neurons are found within the superior and inferior ganglions at, at, at. Their slaves are superior ganglion. And there's R and there's aren't fear ganglion as well with the sensory aspect of the glossopharyngeal nerves. And we have the vagus nerve. The vagus nerve being our quote-unquote wandering nerve, the longest nerves within the body we can see that stretches all the way from the brain, all the way down, all the way down to our viscera. Math, math, there are range of functions. Sensorimotor. It just took a lot. There's a ton of stuff. And so with this just a massive amount of information coming in from organs and on the motor side of things. And a lot of information controlling organs we can see. It goes all the way. At heart, lungs, all of our, all of our visceral organs are real. All the stuff is innervated by the vagus nerve. So massive amount of control that this kind of a catch-all. And width if it's origin for motor signals is the Madu on one data. And this is yet again why the medulla oblongata is such an important part of the brain that if something were to happen to the medulla oblongata and the vagus nerve stops functioning. Look at all the control that would lose if something happened to the vagus nerve. And so that's why that brain stem is so vital to maintaining life. We have our accessory nerve. These are relatively simple in comparison. These are just motor, so these are just controlling the functionality of different muscles within the throat, within the lower mouth. And so for we control the sternocleidomastoid, the trapezius, Paul, ADL, pharynx, and laryngeal muscles. So this was involved with speech generating speech and its origin. If I had a spinal cord and the medulla oblongata, the accessory nerve. It's interesting because it's the only one of the cranial nerves that can arise along the spinal cord just a little bit. It emanates from the medulla oblongata, but a hangs around the spinal cord and use some of that extra, extra real estate in the spinal cord to do it. Finally, we have the hypoglossal nerve, laughter, the cranial nerves, and yet again, another motor nerve which will control tongue movement. And we can yet originating from the medulla oblongata and play it again with control, primarily Tom aiding in speech and generation of speech, and will also control some other muscles of the neck as well. So students, when you're reviewing this chapter, think about them and energies and how they function with the brain. Think about a distinct roles of each region of the brain. Think about the production and flow of cerebral spinal fluid throughout the brain. And then wouldn't revealing the cranial nerves, focus in on what they do and what they're connected to. Have a good day.

sensory pt 2

They're really, really, really cool thing about these very distinct systems. So think of this were something recently found. We're syncing motion. All these function the thing, faith except we had the same basic sensory felt, wired or hooked up to different configurations that allow for sensing all these different, different stimuli. And the workhorse of the inner ear is the hairstyle. Okay, that's called the hair cell because it literally have hairs sticking out the top of it at the tip of each of these. So these hairs are, are cilia, I'll known as stereocilia while a culture of cilia because they'll only move in one direction. Okay? So that will actually, they'll move in two directions. That moving in one direction will activate them. Moving them in an opposite direction, in the opposite direction will inactivate them. And so what happens with with the herself? They use ionotropic activation. So when the stereocilia are moved, either the, these ion gates will open or close and they just physically get opened or closed, allows ions to enter the carousel itself. And so we have here are the stereocilia and here very important. We have the kinocilium. The kinocilium. This is the man that regulate this kind of, is the leader of all of these stereocilia. Kinocilium is what does directly or cilium is sometimes there's more than one. This is what's moved. This is what gets moved by vibration in some way due to something. And this will cause the stereocilia to move one direction or the opposite direction. And so yet again, stereo because we're dealing with, with the two side or two directions. So with this, we have, in this case, if we, if that kinda cilia move in this direction, we open up these, these ion gate, we costimulation if the kinocilium moves in this direction at inhibit this hair cell from becoming activists, from becoming, okay, which is really, really cool. So they were literally opening or closing the gate. And this, and this is all due to these hair cells, primarily the TEFL, with primarily the kinocilium on the turtle being moved one direction or another. And these are sensitive to one direction until we see in different regions of the inner ear. These are arranged and different, and different orientations so that they're sensitive to movement in and a variety of different ways in different directions that are set. So now let's take a close look at how these function within the semicircular ducts that are found within the semicircular canals. And so we have three loops of these semicircular canals. Remember, so the canal, the bony portion, conducted the inner portion so that they're almost interchangeable. And so we have these three loops. And in different orientations we have one that's, that's oriented anteriorly oriented, posteriorly oriented lateral. And so each canal in cases of semicircular ducts, as I said before. And at the base of each of these, we had a region. We have the actual sensory component of it. And so we have here, if an ampulla. Filled with indolent. And then we have the ambulate, ampullae or acute episode cupula is this gelatinous material way or hair cells that are embedded within the ancillary crest, their stereocilia, their cilia, all the Philly or embedded within the ancillary cupula. And what happens is as we move the fluid, the endolymph will move in one direction or another direction within the flute, thereby causing the ambulance cupula to move in one direction or the other direction. So one way to think about this, if you're holding a fishbowl, so you're holding a, a pot of water. Okay. You move and you move forward. What will happen is that that water in that pot has its own inertia. So as you move forward, back, initially, that water in that pot will move backwards. Okay. Because it had its own inertia finding that motion. All right. So with this, yet again, we have the ampulla, and then within that ampulla we have the angular cupula and then the hair cells are embedded within the crust. And then within this gelatinous material we have all the cilia embedded here. And so what happens is that the endless will move one way or another, and this will cause the angular cupula to move. And when the cupula moves, this moves the cilia, thereby activating the herself. So moved in one direction or another direction within a particular plane. So looking at this a little closer to kinda so you can better understand what's going on. So here we have it at rest, no movement of the current. Ok. So here's the cupula not moving. Our, our endolymph is not moving at all. We move in this direction. The endolymph moves in opposition to that, thereby moving the cupula and direction of the endowment. Or if we move in this direction, the endolymph moves in the opposite direction, moving the cupula in the opposite direction so that the, the endolymph will move in the direction opposite of the motion that the whole height of the current. And so what causes us to move your head moving, ok, as you move your head, we have these distinct these distinct ducts filled with fluid sloshing around. And each duct is within a particular active. There's one in each axis. And as we move your head, as you move your head, the endolymph, we'll move opposite to that, to that direction of motion. So for example, if you move your head downward, the endolymph in in that in that canal will move upwards. Okay. Okay. So it'll move in opposition to that most of the, at the head of the whole. And the really cool thing that each semicircular ducts fences motion in a particular axis. So our anterior fences motion in a yes. Direction. Okay. So moving ahead up and downward. Okay. You're setting off that anterior duct, that interior semicircular ducts. We move it laterally. We're saying know what her head. Okay. We're setting off our lateral semicircular ducts and posterior get, get activated when we tilt your head a little bit. So for instance, if your move your head to the left, you're endolymph is moving to the right. If your move your head to the right, you're endolymph is moving to the left. And that is off the material. That is what allows you to motion of your body via your head, even if your eyes are closed. Note for the establishment of ballot, this does get overlaid with visual information. And so this is where see thickness comes into play. For example, if you're in a boat and you're not accustomed to being in a boat, you're watching the horizon to horizon FLAC. But if you're in rough water, your bobbing, your ebbing and flowing with the wave. And then that mismatch of information that will pass seasickness, for example. So within the inner ear, we also have the capacity to acceleration and velocity. And this was done to the ultra cool and factual. So defensive region of the electrical and cycle is called the macula is the name for the entire structure as a whole. So this entire thing is a macular. There's manipulate their thumb actually, okay. Each macula have, have series of herself embedded in this gelatinous membrane, but also their weight it, they have a weight on top of these otoliths, which are these crystals that are above this gelatinous layer. Ok. And so what happens is that this give inertia to, to that layer wad of of gelatin without need, they're needing to be fluid impacting it. Okay, so it's a weighted, weighted thing. Otoliths give weight to this, thereby giving it the inertia, giving it resistance to motion. So what is, what is our ultra cold offenses horizontal motion? So here we can see or article and an a, and a vertical and horizontal orientation. And here we can see our saccule and a vertical part and a vertical orientation. So as we, as we move vertically or horizontally, these will, these weighted crystals will move in opposition to or movement of our total body, and then it will set off those hairstyles. So for example, this is what allows us to sense that we'll going up when we're writing an elevator over, going down when we're writing an elder. And it allows us to sense acceleration, falsehood loudly to sense gravity and velocity. So if you are most prone emotions thickness, this is one of those centers that is highly sensitive. So for people who have vertigo, for example, sometimes there's certain pathologies that caused the otoliths to kinda get stuck a little bit in one way or another. And so if you go to a ear, nose, and throat doctor team, they can put you in a special chair that kind of rapidly kicks you upside down. And it has one method of kind of literally I'm sticking the so they can freely move on their own. Thereby in many cases, not all, but in many cases, minimizing vertigo. So the way these work is that the auto lives have more inertia and the elements. Note the diff. We still have endless surrounding bathing the material. But the functionality of the macula do not depend on on the endolymph, okay, if it's focused on the auto lists that give a weighted top to this gelatinous matrix. Okay? And so yet again, the outlets have more inertia and so this allowed them to move wakes. And so they will, typically, they react differently. So if it's just movement within a plane, what will happen is that they will oppose that motion. So say if this person's head was travelling forward, this otolith would go backwards. But if we have a simple killed, what will occur is that now the auto loan will tilt along because it's weighted and that will stimulate those cells. So for example, if you bend over to, to tie your shoe, entire shoe, when you bend over, this with all the olives will shift forward. Thereby. I sent that your head has shifted forward. Okay. That was a suits moment movement yet again allows for sensing velocity, acceleration, and gravity that dependent upon the motion that's being that you're engaging into, the head of engaging in, you'll send different things. Okay. If you're traveling in a straight line, the auto lift will will move in an opposite. If you're just tilting your head, the otolith with gravity will act upon that outlook and shifted downwards. Okay. I'll also the relative speed at which shifts that allows you to fence acceleration and the rate of change of that, of that direction is your velocity. Okay? The general speed with your philosophy. A lot of meat at sensory perception with this. And so this is where this allows us to sense if we're upside down amount to fill out with defense, if we're fall. Okay. If you're you know, you're in a trampoline or something like that. Bungie dive in or your setting off the defenses as your fall. Okay. So that's a control paul, hopefully. So. Okay. Let's talk about here. Ok, well, hearing in detection of sound pressure waves that travel through from the exterior year to the middle ear and then to the inner ear. Alright, so yet again, we have the cochlea Note that this is, hopefully it does not look like this. It's unraveled to kind of make it easier to see. And so yet again, that coke we have Neil **** spiral and this contains the hair cells. Okay. And so with it within the two, so we have this entire tube that has three sections. So it has at scale or the stimuli a cochlear duct endoskeleton panel. Okay. And then this tube is wrapped up into a snail shaped shaped, coiled into a snail shell, pie-shaped shaped. And so with this, sound waves enter through the oval window and leave through the round window. And so looking at a cross-section of, of, of a tube of the cochlea. What we have here is we have the scale of the city, the light. We have the cochlear duct, and here we have the Galerkin panel. Okay. They have very distinct functions. The skeleton Penn, I'm sorry, scala vestibuli, I'll talk about that when first the scale of the stimuli, what this does is this transmits sound waves, sound waves, pressure waves from the oval window all the way up to the tip of the spiral. And then this meets up with the scale I can pan on. Ok. Then the pressure wave will then travel down the skeleton pan I. And as it travels down the tube, it will cause herself to vibrate. At a travel down, it will cause different regions to vibrate. Thereby these, and these regions are sensitive to different frequencies of sound. And this pressure wave will travel down and then leave through the went round window. Why is it important to have this round window? Because remember this entire thing encased in bone. Okay? If we didn't have a way for the sound wave to be released, pressure to be, to be vented off. The, it would rupture, it would destroy the tissue. And in the cochlear duct being that the kind of middle, smallest of the three. This is what houses in the spiral organ. This is where the actual herself or invent. Okay, so let's take a closer look. So let's take a closer look at the cocoa itself. So remember a cochlea we have are two wrapped around up into the spiral shape. So here the negative space that's generated by that shape, this is the modulus. This is the fight of innervation via the cochlear nerve, okay, which is a branch of the vestibulocochlear nerve. Within this, we have, so coming off of each of the basilar membrane, we have on neurons coming in from our herself. And then these aggregate into spiral ganglion. Ok. So the spiral ganglion will then attach the cochlear nerve and aggregate the information coming from each region. Okay. And so we have one spot was basically have a spoiler, spiral ganglion in charge of a certain set of frequencies. Ok, I think of all the frequencies that we can hear. The human gotta ganglion, a couple ganglia and in some cases, for each chunk, small range of frequencies, which then collectively than get combined in the brain as found. And then we can differentiate speech, et cetera, summit. Yet again, our hair cells are embedded within the spiral organ located right here. And so with this, remember we have, well, we'll get to that. Anyhow. We'll get to this, but remember the scale of the stimuli. This is what transmits from the oval window to the very top. And then that those sound waves, the pressure wave comes and travels to the scale it to pin I, coming all the way down to the round window, getting dumped out. So let's look at this a little closer. So here we have the spiral organ itself. This is within the cochlear duct, right? This is really what it is. It forms the bottom of the cochlear duct and the top, the top of the scale, a companion. Alright? And so width, this is interesting because what happened is that the, it's a little counterintuitive because you'd think based on the other examples of the hair so that we've seen, we think that the actual cilia or what movie. But in this case and as the Herzl to being exposed to found waves, it thought the cilia that are moving, it's the actual herself and felt the soma of the herself that's with being moved. And the, because the cilia are within the tectorial membrane, that causes them to open or close dependent upon if they vibrate or not. Ok, so it bathe the lap, the basal or membrane, the bottom blue colored blue region here. This is what moved. Okay, that's the troll membrane actually doesn't move at all. This is what moves and add this move, this codon, the stereocilia to open or close. Okay. And that it's really and so the issue with hearing loss, hearing loss either due to write things that can cause hearing loss. But one way you can have hearing loss is that through age and or exposure to excessive amounts of high-frequency noise or x loud noise. What will happen is that these hair cells will become detached from the troll member. And as they become detached from this tutorial memory, you can know a lot. They're no longer receptive to, to fan waves in that frequency and that region of the cochlea. And that's where you get diminished capacity for first encountered. And once the tears become detached from the tectorial membrane, the hair cells are there, they're fine. It's just when they vibrate because they're no longer captures their Ctrl memory. We have no, no generation of an action potential. They just vibrate and then that's it. Nothing happens, right? So looking at this again. So remember, so with this we're just looking at our distinct first order, second order, third order, fourth order neurons. Remember that found stuff like a lot of our special senses is associated with particular, hey, can be associated with certain reflex arcs and found is tied to a lot of alertness reflex arcs. So say for example, you hear a loud noise and you kind of shift either free or you immediately look in that direction. So there's a lot of different reflex arcs associated with things. Okay? So note that this is kind of nice because here, what we're showing off here is different regions of the cochlea that are sensitive to different frequencies of sound. Until one. Remember once you found that convolved with adults bring, coming all the way down here with first year low-frequency than our medium frequency and all the way to the high frequency. Typically with old age, we start to lose the ability to sense high-frequency found first that just various based on what you're exposed to. So the sensory nerves carry the found information from the cochlea nerve to the cochlear nuclei. Then it all travels down to the distributor vestibular nerve. Okay? And then with this, it enters the palm of literary nuclei and then through the empirically glad midbrain, ok. And then from here were transferred to the superior olivary nuclei. And then here we have our first major site of profit thing and the inferior colliculi. Okay. This is where all these other regions, this is where we're just bringing together input of the different frequencies from the different frequencies. Yet that occurs through ganglion here to some degree as well. But this is where we're just kind of relaying information. It here at the inferior colliculi. This is where we have a lot of motor responses to sound. So startle, startle affect breathing and that sort of thing. Then via this ascending to the genuine nucleus, this is where we start to see more appreciation interpretation of sound. Okay? And then finally here, within the temporal lobe, this is where we get further, further processing of that found input. Where we see speech patterns, we hear words, music, different types of fountains, also width, if also with this as well, we have to remember that because you're traveling through the thalamus. We also have interaction with, with all these regulatory portions of the limbic system as well. So here, this is where sound can elicit certain memory can be tied to certain emotions as well. And so that's where we have that, that meshing of, of emotion and in sensory input. Okay, so, so that was for sound. Let's look at for balance, okay? And so for the distributed complex and for dealing with equilibri, equilibrium to this, but what the root of what it does allow us to stay effect, okay? A person with an impairment of equilibrium cannot stand or can't even fit upright, they will fall over because they don't know. They can't fit using their inner ear that they are erector not okay. They don't know if they're upside down or not. All right, and so now with this, we have a lot of sensory organs and the vestibular ganglion McKay to incorporate information from each of the semicircular canals. This will join into the vestibular nerve and then join it to the stupid coplanar. Okay? And then width, this will go to the vestibular nuclei. And this is between the pons and the medulla oblongata. And now this, hear this information. There's a lot to this. So this will, a lot of this information will go to the cerebellum. So this aid in maintaining balance, alright? From and from the vestibular nuclei, we also have information that will go down, go down through the spinal cord, especially to this particular track to aid in maintenance of body position or posture. Alright? So this is where we get the somatic reflex arcs. Maintain posture when we think of negative pot, when we think of path that posture, you're sitting in your chair right now. Okay. The reason why you're sitting in your chair and just not falling on the floor is because we have reflex arcs that are maintaining our posture, maintaining fitting, meeting, scanning, meeting Milwaukee, alright. Associated with the thoughts that we have, the red nucleus. So this is also from movement of motion as well. And say for example, with somebody who has very extreme Alzheimer's or very extreme parking for them that they have difficulty sometimes walking because they have an impaired capacity for something, Bout for something equilibrium. And then we have further information go into superior colliculus as well for different for different reasons, especially when we're dealing with fencing, acceleration and velocity in gravity as well. So, and this, and this information is important here because think about when you're running, when you're walking, okay? One of the ways you can assess and regulate the speed at which you are moving is through the saccule and U, ultra cool. Okay? This is what lets you know that what you modulate the rhythmicity of you're walking away from the city of your motion. Also think of how you hold your body up erect or passively as you walk or as you run or as you jock. Okay. So running, jogging, walking, or three distinct patterns of locomotion. They all have their optimal speed, they all have their optimal efficiency. And so we can shift between these almost pointlessly by assessing the velocity and acceleration that we're undergoing. Okay, as we were traveling, we have the velocity, as we shift, as we have a change in velocity, that is acceleration and so on. Down we see a shift in the acceleration. When we speed up, we have a shift that acceleration and all those, especially to the cerebral cortex, to then coordinate conscious motion. Conscious control of running, conscious control of walking. That is where the special senses are really vital. Especially in particular, our inner ears for the sense of equilibrium. Because if not allow, not only allows us to walk without falling over, but this helps us modulate our speed of walking or running, or jogging, or even jumping or leaping, you know, that sort of stuff. So really, really important for, for overall motion. And so with this also within the vestibular nuclei, we also integrate information from each side of the head. There can be cases where an individual has when 5x that's impaired. Typically, they're acted in tandem. And yet again, we're sending information cerebellum, cerebral cortex and motor nuclei to establish posture, establish muscle tone to enable walk into naval motion to enable standing. Okay. And then with this, as far as other nerves that are so step that take information from from this region as well is from the vestibular nuclei, is we have oculomotor, trochlear abducens and accessory nerves, all allowing for particular motions and for controlling different systems that allow for effecting motion and controlling our emotion and bringing information in about how we're moving as a whole. And then yet again, these motor, motor commands are sending down to the vestibulospinal tracks for controlling different regions of skeletal muscle. Because even whether it be a, a reflex arc, symmetrically flux luck, or conscious control. It all comes out of spinal cord them when we're dealing with the bulk of somatic, control, the buckling for somatic reflexes. Ok, let's talk about mutation now. Okay? This is the last of our special senses that will covered. And so with that, let's talk about the I of the whole game. So we have a whole host of accessory structures for the I, the support, the ideas, keep the faith and hydrated and protected from just think in general. So we have our colleague Greg, which are islands. Ok. Looking at this underneath them we have these tarsal plates, which are the bulk of connective tissue forming the eyelid. Alright. We have our tarsal glands. Okay, and so our toast or tarsal glands, these are sebaceous glands that keep liberate from sticking together. Okay, and so this is, these are important because if it wasn't for the oily oily thumps when the delivery with protected your eyelids would be feel shut. Alright, and then we have our current electrical uncle, what you're sweating subshell going to be his client. Leave yet again, support the Palais Bray as well. And then on the surface of the eye went off with the inner surface of the library. We have our conjuctiva. So when you have, if you've ever had pinky that's conducted vita. Okay. And so the anterior portion of the eye, the visible portion of the eye, this is covered with our bulbar conjuctiva. Whereas in the inner lining of the eyelid that felt palpebral conjunctiva kept the inner lining of the, of, of the islands themselves. Note that we have a whole host of, so the lacrimal crumple there, that is where we have a whole host of lacrimal gland fitting. We also have lacrimal gland associated with lateral portion as well. The lacrimal guys will talk about the tears that they produce. But of note, with within the LACMA, her uncle, we also have a region of drainage for four tiers themselves. Let's talk about the lacrimal apparatus to little, a little more closely. So tiers are produced by the lacrimal gland. We have our lacrimal gland laterally, whereas we had the lacrimal sac that terrain. Those tears away and shed out from, from between the polymeric tube fell alkaline also to lottery mixture have lysosomes and antibodies in it yet again, for binding to pathogens to minimize their capacity for invading the body and for taking advantage of the self. And so with this when we're dealing. So here we have our lacrimal gland. Here's are secreted through these lacrimal duct and are secreted throughout the calibrate. And add the travel along we're along the, the bulb of conjuctiva. They'll come to the lacrimal. I pumped them and Pang Kai and curricula and then drain into this end to this region, drain into lacrimal sac, which will then eventually empty into into the nasal cavity itself. Ok. With this, while you're sleeping, you're Klocal. I bogie that craftiness of your eye. That's just any material that some of the sebaceous glands that but keep your eyes from the, keep the delivery from sticking. But also just precipitates from from the from the tears kinda forming in that drainage region right there. So here we have the i itself. So here we see our calibrate. So there's lower eyelid, upper eyelid. And then we look at the conjuctiva real quick. And so here you have the **** people were conjuctiva right here underneath the eyelid. And here we have the bulbar conjuctiva right there and the portion of the eye that exposed. Note that it does not cover the cornea and it jumps right up against. Covered according itself proper. And so when we think of BI, we think of a sphere within a sphere within a sphere. Okay? So we have these different layers. These are also known as tunics or Coats as well. And so with this, we have the fibrous layer. This is the sclera. Okay, there's primarily the sclera also. This is the cornea. This was what good structural integrity to the eye rather than the eye works the way it does because we actually can develop fairly high pressures within the eye to maintain tissues where they stand to maintain the lens in its proper position. We have the vascular layer. This is the chord. This is a choroid. This was when we looked at your sheet I. These are the black later within the i. And then we have the inner layer. A subset of the inner layer is the nervous layer, or nervous tunic or nervous coat and that the retina itself. Okay. So and then within the i, we also have different faith. Okay? And so we have our anterior cavity. So our interior cavity is from the lens to the cornea. And our posterior cavity is from the lens to the very back of the eye, to the, to the retina. Alright. And so within the anterior cavity. Okay, both of these spaces, so we have these posterior and anterior chambers within the interior cavity. It's a little confusing, but it's just the way it is. And so what, what does follow us is the anterior chamber is from the cornea to virus. This front little bit right here. Then from the iris, the lens that the posterior chamber. Both of these regions which make up the anterior cavity. The fluid that found within it is aqueous humor. Very, very ready. This is compared to what's found in the posterior. Kept remembering the posterior cavity. This is from the lens all the way back to the retina. That is vitreous humor. It's very jelly like thick. Alright. Also note looking at our layering. So here we have our fibrous coat or fibrous layer. So here we have the sclera and the cornea. Alright? Then we have the quote right, running along the midi layer and when. And then preserved pie that looks black. And then we have our inner layer, a war neural layer. The subset of the interlayer is neural layer that has the retina, the inner portion that has the actual sensory soak them felt. Remember the choroid is what feed to the eye. And then also a posterior to the eye not shown here. We have there's always a padding of fat. And this just helps to keep the eye and plate also not shown here. We have a whole host of extraocular muscles, so they've somebody undergoes a massive amount of weight loss. This is wider iBooks sunken in. So here we see a slightly different view of the eye. So with this, we can have a better appreciation for the anterior cavity where we can see the anterior chamber and the posterior chamber right there yet again, between iris and the lens. For the interior chamber between the cornea and the iris itself. Also, within this view, we can see, or at least appreciate a little bit better the different layers of the eye. So here we can see our fibrous are chloride or bachelor, and the innermost portion of the neuronal, the retina itself. Also here we can see the orbital fat keeps the eye in place, giving it shape or keeping it within the orbit to a certain degree. And then also here we can see the two some extra ocular muscles that allow promotion. And we got one thing that I want to highlight here, which is a really important concept to think about is the optic disc. So the optic disc is important because the fight of innervation of the eye. This is also the flight where on vasculature enters and exits the eye. And so at the optic disc itself, we do not have the capacity to sense photons because remember that's what vision is based on. If a being able to photons. So if we were to think of the eye, so if we put the I had half over the square root of the wooden bowl. If we then had the chloride as a piece of felt, and then we had the retina as a piece of cellophane or something like that. And we put a thumbtack and when spot, that would be analogous to the object if the portion that's anchoring everything together because it is from the optic disk where we have that mature entering and exiting the IGM. And it's where we have innervation, where we have the optic nerve leaving the eye as well. So let's take a closer look at the layers. The fibrous I've already talked about a bit. To the fibrous layer is primarily made of the sclera and the cornea, which gets protection gives anchoring point for the extra ocular muscles. When we're looking at the cornea, cornea being specialized portion of the square. Remember the corn, it is semi-transparent, allowing light to travel through it. The reason why light can travel through it so easily is because they've asked for there is no vascular vasculature running through it. There's why light can travel through it without being impeded. The outer surface of the cornea has stratified squamous epithelium. The inner surface has a simple squamous epithelium. And yet again, what allows for material exchange and keeps the cornering alive is that aqueous humor that fits within the anterior cavity. So let's talk about the vascular layer. So the vascular layer has two main regions. We have the core, right? So this is the region that highly vascularized. This is what's directly between the retina and the sclera. And then we have the ciliary body. So ciliary body with its, we have or Serrano which is the posterior edge of it, or the ciliary body. So it's kinda looks almost like a ruffled region. And then with this, the ciliary body felt what we have are the ciliary muscles and the associated epithelium. And if the ciliary muscles, which are smooth muscles, this is what causes accommodation. And the I used to work opposite focusing in the eye, the smooth muscles that act upon the lens to focus an image on a different region of the retina dependent upon the distance of that image of an object to the eye. With us. We also have the ciliary prophecies that connect the lens, that connect to the lens via suspensory ligament. And this is where the filler metal act upon the len self. And yet again, accommodation is altering the shape of the lens. That, that's what, what causes focusing itself. So let's talk about accommodation. To accommodation is focusing of the lens, focusing of an inch. So what happens? Very much just like the cornea, the lens that's also a vascular. It is that in a ring derangement of elongated self and connective tissue, then because it's a vascular, light can pass through it because the shape, it acts literally avid, namesake a lens. Our vision is unique in that are perhaps a version without having to undergo massive amounts of accommodation. And most people is attuned to objects that are far away. Okay? There was one, unless you have something like say, astigmatism or something like that, naturally have very clear vision of objects that are far away. As we, when we want to focus in on something that is close to it. Looking at upcoming course or reading what have you. This is when we have to engage accommodation. This is when the ciliary muscles have to pull on the filler ligament hole on the land. And that causes it to change shape, thereby changing the focal point of that image of those photons coming in to a distinct region of the retina. And so when an object as far away as photons bounce off of it, it's within focus because it fall. Fall, it gets projected on a, on a reasonable region of the retina. Once we have a close up image and the ciliary muscles are relaxed, it, where the image is being, is being projected onto, is beyond the scope of the retina. It's blurred. And so what happened is that then we have accommodation, we stretch and pull. We contract the ciliary muscles through parasympathetic fibers. So yet again, in a visceral reflex arc. And then we cause a, because of rounding of it, of the thought and the harvest focusing of the object on the back of the retina gets projected properly in the back of the retina. This is why with age, most people have to use reading glasses because as we age, the elasticity of the lens will decrease. Okay? And so that's why most people at the age will eventually need reading glasses to be able to improve the capacity of the length to properly project images onto the retina. Most people, even an old age, still retain the capacity to objects from far away. But most people, as we age as the, as the length is elasticity and becomes harder, we need reading glasses to hate them. And so we typically undergo accommodation. We always go under undergo accommodation when we're trying to focus on an object that's close to our faith are relatively close surface. Let's talk about this last region of the vascular layer, the iris. Would the Irish, there's the Irish modulate how much light is coming in to the I based on the amount of ambient light that's available. And so that is what causes stay tokens based pupil constriction or dilation of the pupils. So remember we have the iris thought the pupil is the opening at which where photon enter the I, enter, two photon enter through the cornea. We have the aperture of the pupil, the opening of the pupil formed by the iris that allows photons to come into the lens and then hit a certain region of the retina. The Iris who's made a blood vessel pigment, is where we get our eye colour from, which is genetically predetermined. There are some things that can impact this as well. Ontogenetic or Uh-huh. And then smooth muscle. So yet again, this is controlled by a by visceral reflex arcs. And so yet again, this just dictate how much, how many photon in math can come into the eye when there's a lot of ambient light available, we see constriction of the pupil. When we see low amounts of light, ambient light available, we see dilation of the pupil. They, the iris is relaxed. And so with the really neat thing, that's what allows for altering the shape of the pupil is we have two sets of muscles. We had the sphincter populate and the dial, a dilator papillae and fell these tooth that contradict each other. And so what we have here is we have the dilator populate, which are radial. And then we have a thing to populate, which is a circular ring. And so when we want contraction or a constriction of the pupil, the constrictors contract and reduce the size of the pupil will want to cause dilation and we want to have a very large pupil. The dilators contract, thereby stretching out the constructor and opening up that pupil, which is great. So here we can just see slightly. Their view of the iris itself. Also here we can see the ciliary body itself and the ciliary prophecy that attach via ligaments to the length of stuff. Alright. And then also here we can see our bandwidth for their muscle, which are what will pull on the lens to cause accommodation to occur. So here we're going to look up the inner layer where the retina is found. And so when we're looking at the entire region right here, this is all, this is the inner layer. The pigmented layer is the outermost region of the interlayer. Non neurone. We had been wrong layer, which is where we have all the neurons sensory felt, and we have the photoreceptors that make up that Britain itself. So for photo receptors, we have two flavors in the eye. We have rods and cones. Rods to light. In general, cones are tuned to very specific wavelengths of light, thereby specific colors. The pigmented layer, this outer layer, it aid in maintaining our our photoreceptors and the other neural cells that are sitting within this layer and fill with it. We have it, the whole host of accessory neurons. And what these do, these aid in combining the information being, being generated by these photoreceptors. And some with bipolar cells. These directly communicate with either typically small bundles of photoreceptors. And then we have horizontal so that, that, that communicate between photoreceptors, bipolar solved with amacrine cells. And these modulate communication between bipolar and gangrene felt almost like a pyramid scheme where they wear a one-stop when levels talking to another and slowly but surely aggregating the information that's coming in. And then finally, we have the ganglion felt that DDS will aggregate into bundles of axons are what form the optic nerve itself. Proper cities, ganglia and v thermal to the government so that the sum of whose neurons will end up forming the optic nerve. So let's take a closer look at, at our photoreceptors. So we have our rods, we have come to really clever and that are rods look like rods and cones look like cones. Or comparing the two distinct types of cones come in three varieties. In humans, animals have a variety of different types of cones. That's why some animals can be UV light. For example, we have three types of cones. We have red cones, green cones, and blue coats. This is why our primary colors are red, green, and blue because we have a cone per, per each one of those colors. Color vision depends on high amounts who'd like to function. This is why our color vision diminishes at night. And here we can see are our pigment epithelium supporting our, our photoreceptors. The interesting thing about the way light works, as it hit the eye. All photoreceptors are pointed. Are pointed outwards. Okay. What happened is our photons come in, bounce off and then hit the photoreceptor. Some will hit the photoreceptors on their way and no problem. But a lot of them that along with photons, will bounce off and then hit the distinctive photoreceptors. So that's just one of the quirkiness of the retina as you would think that it would be advantageous for your, for your photoreceptors to be pointing outwards. But this kind of allow for, I guess, for lack of a better term, bank shot from photons to reach these these photoreceptors. How do these photoreceptors work? So vision itself, metabotropic signal transduction pathway. What happened is it's all about the rhodopsin. Rhodopsin is a membrane-bound protein that is sensitive to photon as a whole. Within rhodopsin. Rhodopsin, sorry, we have a particular protein called retinal. Retinal depended upon if we're in a Kono rod or a specific type of cone is sensitive to a particular wavelength of light. What will happen if that, if that retinal is hit by a particular photon of a particular wavelength, that will cause a conformational change in that protein, which will then and initiate this entire signal transduction pathway causing polarization, thereby causing an action potential to occur. And so this is where we have a retina all sensitive to different wavelengths. So we have rods sensitive to a particular set of wavelengths or a region of wavelength versus blues, greens and reds. And so, and that's what give the functionality of each type of photoreceptor cell only compare the sensitivity of these wavelengths. This is what we see. So here's our wavelength of light. So we go from purple to read. And here we have our rod. Rod can, can be stimulated by a photon from this wavelength to this wavelength. Alright? And what, what this shows here, that the optimal wavelength that they function, and all of these have an optimum. And that's just where we, where they get the most activation that film. And so here we see our blue being activated by the entire wavelength. Here with the green and our green cone and a red cone being, being activated by, by those distinct wavelength. Alright? And so what happens if a rod is hit by a photon in and this wavelength, nothing happens. Okay? If a red cone is hit by a photon and this wavelength, nothing, it doesn't stimulate that written up and the focal point of the written law. It only reacts to being hit by a photon of a particular wavelength. So there is a, there's variation in where rods and cones can be found on the retina than not just evenly spread around. There's, there's a distinct places whether at higher densities and the rods are concentrated on the periphery of the retina. And that is because remember, rods are sensing general light, okay? Just, just, just if it is there like or not, can we see stuff? Alright. What we have is a region of the eye called the macula. Ok. And what the macula is, is when we're viewing completely straight at something, when, when the image comes when completely perpendicular to the axis of the eye. This is the root. The smacked with macular region has macular, it consists of only cone, so only sensitive to, to red, blue, or green light or photons. And so within this region, we have the flow depth and travelers. And so at the fovea centralis, which was the center of the macula. So if you think of that, the fleet spot, the flow control is like the bulls-eye of that sweet spot, the very, very center of it. And it's at the site where we have our best contribution. Also, this is where, where our eyes are properly aligned to an object. This is where we get the most differentiation of the object, where we get the best color vision. And yet again, when we're looking at the optic disc, the innervation of the eye, at the optic disc, we have no capacity to send photons. Okay? This is also called the blind spot because there are no rods, cones. We can't extract any photon that at those two points. And this because of all the axon leaving the eye and all the vasculature coming in and exiting artists coming in, things coming up. Okay, let's talk about the humors. The humors are important because the humors feed regions of the, I. Especially remember that we have these region to the eye that are completely avascular. We have the lens, we have the cornea, and the aqueous humor is secreted by the fell, the ciliary body. And so here and the little red arrows we can see the pattern of secretion. So here the ciliary body making aqueous humour. And so our aqueous humor primarily focuses on the anterior kathy. All right. So the, the aqueous humorous is formed by the ciliary body, emerges outwards from the posterior chamber through the anterior chamber, circulates around and then is drained by the scleral venous sinus. Yet again, here we have another scientist training stuff away. Okay. What does the aqueous humor do as we've seen time and time again, whether there's any type of fluid there. It is the medium for exchange, exchange gases, exchange of nutrients, keeping the Korea livelihood the cornea is living tissue. Add, add the lens to also living tissue. Remember our cornea and our lens or big globs of a vascular tissue that need to be kept alive. And they're kept alive by this aqueous humor providing a main for, for exchange. With this. It flows outwards. The posterior to anterior cavity, through the entire anterior cavity. Some of it will count secrete outward than backwards towards the posterior cavity. But if the minimal amount, it mostly what we have is, is kind of surrounding coming around the length and coming out into the anterior cavity, which then get sucked up into the square of the defenders. So somebody had the glaucoma. Okay, they have increased ocular pressure. Typically what happens is there's something goofy happening. Either their ciliary body is producing a lot of aqueous humor and generating too much pressure. Or they, or there could be something with the scleral venous sinus that it's not training enough. That's when you have too much intraocular pressure. We can also have too little intraocular pressure. So if we have too little interocular pressure, what can occur is first and foremost, we can have starvation and blend them the cornea in extreme cases. But also we can have, we'll get to this a little bit. Certain regions the I will peel off the wall because its the fluid. Whether that youth are aqueous humor that kinda keep that in place. Okay, so let's go to that to talk about vitreous humor. You remember the vitreous humour. Cavity BI, very gelatinous sphere, very thick wire as the aqueous humor is running. Okay. Not very viscous versus the vitreous humor is very mature, very discuss. The vitreous humor is important because this is what really helps shape the eye. This is what puts pressure upon the sclera could give that rounded apparent to the eye of the hole at A1 supporting the lens, the position of the limb that keeps the lens and plate. Also the really important thing with, with the vitreous humor that it keeps the retina and play. It happens to some people to old age and there's also some pathological that can cause that you had a refeeding or decrease in the pressure caused by the vitreous humor. And then what literally happened is the retina starts to fall down like all wallpaper. And that will create a multitude of blind spot on the retina, which it propagates too much, is a very, very bad thing. Note, as I said before, the aqueous humor can flow across the vitreous humor into the retina. But that not, it's just, it's just more of a chaotic thing. Metaphors oozing out in that direction. The bulk of it will still come into the anterior cavity and be drained by the sclera being a sinus. So let's talk about the pathway of photons in the eye because that's what this is all about, bringing photons in and then fencing them. And so what happens is we have lightwaves, the pass-through accordion. These pass through the aqueous humor. Then the size of the pupil allows a certain amount of photons in the past the length. Then those photons pass through that your humor. And then due to the activity of the length, they are focused on a portion of the retina. Obviously, if it is a image that is far away, we don't have accommodation occurring. But if it is a close-up image, then we have to have accommodation, stretching of the lens too. Shake to allow for focusing on those photons on the retina. And remember really what the image, the image is irrelevant. What we're doing is we're just, we're making sure that the photons are hitting at an optimal part of the retina. There's only a photon hitting the retina. Okay? So when you're staring off in the distance and something in the foreground, if you're focusing on the different, passively focusing out in the distance and something close to youth Havi, it's just out of focus. Those photons bouncing off of that object is, and how we see things are still hitting your retina, but they're not hitting in a way that we can form a concrete or clear image through accommodation where we can see these images closer. This is also why, for instance, why you, your, I feel quote-unquote tired after reading a book or a computer screen, what have you is because to actively being actively feet something near your, near your faith, you have to undergo accommodation awhile, staring off into the wild blue yonder. It. You don't have to undergo accommodation. Your ciliary muscles are relaxed at o and stuck it to the image and some part of the retina. And then we have depolarization of photoreceptors. And then those photo than those nerve impulses are transmitted via the optic nerve. Here we can see the result of all this. Here we can see the result of the, of the photons come into the right, either photons coming into the left eye. Note, we have what's called By knocked to the vision. Most vertebrates have this that have their eyes on one plane where the images become overlapped and then through the activity optic kayak and they get basically swapped around some degree where they become integrated with one another. All right, so let's talk about how this works. So this process is called cortical integration. This is where we have where we have visual images, visual information from one eye, integrating with visual information from another eye. And so what happens functionally, it is crossover of the optic nerves at the optic chiasm. And so what happens is the following. We have images from the lateral portion of the eye, okay? And then we have images from the medial portion of the child, the lateral portion of the chyme that ends up going to It's respected hemisphere in the brain. So you're right lateral image goes to the right side of your brain. Your left lateral image goes to the left side of the brain, but your medial, medial section of your image. This gets swapped at optic Kias. Okay? So you're left medial portion of your, of the photons that you're, that you're encountering. These go to the right side. Your medial photon that receiving the image that's generated by the, by the medial portion of your retina from the right side goes to the left side of the brain. And that's really it. This allows for overlapping of the, of the image. And last for integration of the image, better integration of the image and, and, and more of a seamless transition between the visual input from both eyes. Okay. So with this, we have the visual information that come then. Note that it will go to other portions of the eye that really don't have much to do with actually a width forming an image on interpreting an image. Say for example, the pineal gland is activated based on how much light we receive in the eye. Okay, for example. And that's under the, the control, the super high asthmatic nucleus. Now that relay that information onwards, the bulk of our visual information gets processed. A lot of it gets processed by the superior colliculi. And then the rest of it gets, gets, it arrives to the visual cortex of the occipital lobes. Ok, where we, where we kind of piece it together and, and interpret the images that we're seeing. So the signal coming from the lateral geniculate nucleus right there, these will either synapse in the superior colliculi or the super charismatic nucleus of the hypothalamus within the superior colliculi. What this will do is this will aid in controlling subconscious head, ie, an ECMO, movements that are associated with visual stimuli, basically aiding and clear movement of the eye to allow for stable accessing of that image is stable. Capturing an image with the supernode math nucleus of the hypothalamus. This will, this is involved with the amount of light perceived which will eventually down the road impact the amount of melatonin that's generated by the pineal gland itself. So as you review this chapter, think about in general, are, are ionotropic versus metabotropic signal transduction, which one is used per type of sense? Think about our tonic versus phasic receptors and how those interplay with especially our general license is thinking about how the body uses generalized sense is mainly for Intel reception, proprioception and things of that nature. And then also think about the, each of the special senses, their unique anatomy, their innervation, but also how do they work? Which ones are ionotropic and which ones are metabotropic?

nervous

Listed in this chapter, we're going to talk about the nervous system. We'll talk about the different cells that makes up the nervous system as a whole. And then we'll talk about their distinct rules. Alright, let's get started. So with the nervous system that allows the body to undergo rapid communication within the body, it can control and adjust activity the body at a very, very rapid pace. It will provide swift, but re, responses to stimuli can maintain homeostasis. So anything that's an immediate, very rapid response that is short-lived, that is under the purview of the nervous system. And you can minuss long-term chronic regulation that's in the purview of the endocrine system and nervous. Actually the integration center for reflex ups aisle both somatic and visceral reflex arch that revolve around sculpt the muscle somatic, and those that revolve around everything else visceral, the integration center is what receives this information and decides what to do, what effector organ is activated. Nervous System is also the place for the interpretation of the special senses. So fight teeth, found things of that nature which will cover all those senses in a later chapter. And also the nervous system is the center for memory, learning, thought, personality, consciousness, communication, emotion. It is the center for what we are as an individual, not only our thoughts, dream, desperation, memory, learning, et cetera. So when we look at the nervous system, we can separate it into two main categories. We can look at the central nervous system and the peripheral nervous system. The central nervous system is composed of the brain and the spinal cord and the peripheral nervous system and everything else, all the other nervous tissue that is found throughout the body. And so with this, but the central nervous system, this tissue is for integrating, prophecy, coordinating So brings in sensory input, send out motor output, makes things happen, also, feed for higher brain function. So personality, thought, memory, learning, language, all those things. The peripheral nervous system, that is all the tissue outside of the central nervous system that's connected BY, that's connected to the central nervous system, allows for these prophecies, for these orders to come out. Also, this is the mechanism or the route where information lead to the central nervous system and how information is sent out. Orders are sent up from the central nervous system. And so we have, and with this, we have a current division or ferric division. A ferric division bringing things to the central nervous system, bringing information to the central nervous system. Let's begin at the sensory receptors themselves. And then we'd have the effect division, which send motor commands from the central nervous system which end effector organs. Something is happening. There are orders being carried out that originate at the central nervous system. And peripheral nervous system are the mills that are attached to the central nervous system, allowing for information to come to the central nervous system and for information to leave the central nervous system itself. Something at the information that comes to and leave the central nervous system. We can see we've got a thirt information on an ethernet information. Now, looking at this diagram here, we can see what's happening within the CNS, what's happening via the PNS, peripheral nervous system, tissues outside of the central nervous system. And then what's happening with our receptors versus art defectors. And so for a thirt information, we have somatic information coming in. The extent to what. Muscles are contracted or not contracted or they're lifting tension, thing like that. Visual information, a whole host of things to stretch receptors to pH values. Here two values, et cetera, and then information from the special sensory receptors. So Taste found, fight, things like that. And then for ethernet, these motor neurons that are leaving the central nervous system sending out information. These will either go to the somatic nervous system where we're controlling skeletal muscle, telling skeletal muscle to, to do stuff typically contract, sometimes relax. And then we also have the autonomic nervous system, which is separated into the parasympathetic division and the sympathetic division, which we'll talk about in a little bit. Both of these divisions have either speed up or slow things down in general, but we'll get into more information about that. And then we also have specialised nervous system, the enteric nervous system. We really don't talk about that when this much of this course, what is basically to be quote unquote brain of the gut. All the prophecy that occur within the gastrointestinal system literally have their own subdivision. And this is the enteric nervous system in older tech get taken up by the ANS, but it does, in more modern texts have its own division, which your book doesn't really go into a whole lot of detail. So I'm not going to really go into specific limit, but just be aware that the enteric nervous system, this is one of the wave that your entire gastrointestinal system can synchronize all these activities at a very rapid rate using nervous tissue versus ways that they, that the gastrointestinal system can regulate itself via hormones for chronic regulation of punch. But yet again, the enteric nervous system kind of gets wrapped in with the autonomic nervous system because we're controlling visceral, controlling smooth muscle versus the somatic nervous system. Yet again, it's solely controlling skeletal muscle only. Here we have a reflex arc. We've seen this before, but let's just go over it again just to review. So here we have an entire, we've put Talk, which is an automatic pathway that mediates responses. There's some type of stimulus that reaches the central nervous system. And the central nervous system responds to that and conquer some effect. In this case, we're looking at the classic withdrawal reflex when we touch something hot and we rapidly withdraw or hand from it. And so there's fire, fire, bad fire hot. It sets off the receptors in the hand, sensory receptors in the hand of pain receptors in the hand, the information via sensory neurons to the integration center. This a third pathway sending information to the central nervous system. The integration center, and this case the spinal cord is the integration centered. The brain can also act as the integration center. And now after this information, the spinal cord, it will send via the efferent pathway some type of action due to the stimulus, due to this inflammation. And so with this, we're sending, we're sending orders through the motor nerve to the arm muscles to cause withdrawals, to move your hand up because our, you touch something hot. Alright? And so with this we have the sensory receptor, a fair neuron, sensory neuron Integration Center. We have the efferent neuron, a motor nerve in this case I'm not infected organ in this case I'll arms, muscles in the arm to move the hand out of the way. Note when we're looking at these different reflexes, which we'll talk about more later. We have our somatic reflexes that are solely skeletal muscle is involved. So this would be. A, a example of a thematic reports. And the way we classify reflexes is based on what's happening on the east side of it. If we're going to, if ultimately skeletal muscle ON leaves being stimulated than we're dealing with a somatic reflect. If all other types of tissues are being stimulated, that we're dealing with a visceral reflex where we're looking at smooth muscle, cardiac muscle or gland and article isn't a hope everything else in the body. So that's how we're going to classify these reflexes. Remember truly if Mozart is innate, not burned. You've got the divisions of the autonomic nervous system. So we have sympathetic and parasympathetic. In general. Fight or flight is sympathetic. So in general, the sympathetic system will speed up the activity or increased activity, even Oregon, when that system stimulates that Oregon, vs. the parasympathetic system, which in general, when it stimulates the organ or tissue, it will slow it down. Or tied to particular prophecies. Note that these are not hard and fast rules, but just generalities between the sympathetic and parasympathetic systems. Sympathetic speed up, parasympathetic slows things down. There are scenarios where the sympathetic system will slow things down there. Scenarios where the parasympathetic system to speed things up. But this was just a painting with broad strokes. But note that a whole host of different organs are innervated by both of these systems, thereby allowing for different levels of control, where we have control exerted by the spinal cord for a lot of things with spinal court acting as an integration center and a lot of things where the brain is acting at the integration center, controlling things. And the thing to note depended upon which region of the spinal cord we're looking at. Also lets you see how if somebody gets some type of damage, physical damage to say they're sacral vertebrae for example, and tackle portion of the spinal cord. They will lose functionality of different regions of the body because of that, the Integration Center had been destroyed or damaged, or just those neurons, those nerves have been feathered. It can no longer communicate either orders or information to and from that portion of the, of the integration center of the central nervous system. Let's look at the main cell types within the nervous system. We have to generalize categories. We have on neurons and we have a neuroglia felt, or glial cells, or neurons are highly specialized, felt. These are what allow for the rapid transmission of information through the nervous system. Neurons that form, we have junctions of neuron that form nerve. And he felt that allow for information to rapidly move throughout the central nervous system and the peripheral nervous system as well. Then we have the neuroglial felt. These can readily divide. These are the supporting felt that are found within the central nervous system and the peripheral nervous system. So these will protect, regulate, repair and enable neurons. Are, neurons are like the featured artist and the neuroglial falls or the road roadies supporting the activity of the neurons. All right. So looking at a neuron within the stereotypical neuron, they come in a bunch of different flavors from this. But what we have is one region that will receive information. Then we have the transmission of information along the length of the phillip tough. So we have dendrites that are receive information that fell body establishes. Homeostasis of the cell also allows for the signal from the dendrites to build up and will elicit an action potential at the axon hillock, the axon itself, that is what will rapidly transmit the action potential along the length of the act, along the length of the film itself. And at the axon terminal, this is where that signal, that information if is as in part a to other cells. Okay, transmission of information along the axon occurs very, very rapidly. But let's now focus on the glial cells will talk about neurons more and a little bit. There's a distinction between which ones are found within the central nervous system versus the peripheral nervous system. And they have different roles in each. Looking at central nervous system. The thing with the central nervous system of the central nervous system is almost its own ecosystem within the body itself. It's a very exclusive gated community within the body. And in part because we're trying to protect the central nervous system, which is very, very delicate tissue from the rest of the buy from pathogens, et cetera. Also, by establishing its own, its own system. It's almost its own subsystem within the body. If flight me buffered against fluctuations of physiological parameters within the body at the whole lightly buffer, not completely buffer. And so with this we have our astrocytes, oligodendrocytes, microglia, an epidemic folks are astrocytes. These are the most numerous. These make up the blood-brain barrier of where material can't just mentally go into the central nervous system itself. These also form scarred central nervous system, and these will recycle neurotransmitters that are being emitted by the neurons themselves, the oligodendrocyte, these are very important because these will form myelination sheeps or which will also form into nodes along that, the sheath along the axon. It's the myelin sheath that allow certain axons to transmit information very, very rapidly. Not all neurons have a myelin sheath that microglia need to fake aesthetic felt. These will just destroy stuff. Just in general destroy the glial cell, the short neurons if they become damage, things like that. And then we have the epidemic holes. These are very important because these produce EFF, cerebrals, the final fluid. And they will also monitor cerebral spinal fluid as well. The entirety of the central nervous system is paved with, with through the spinal fluid. This is the medium where we have exchange of materials. And so what happened due to other factors that we'll talk about in future chapters. The blood supply that goes to the central nervous system exchanges material with cerebral spinal fluid. And then the cerebral spinal fluid itself with an exchange material with the self of, of the nervous system, okay, at a medium that has a whole variety of functions, we'll get to later. But if the mechanism of exchanges is what all the cells are bathed thin and thick and revise it. The presence or absence of myelination will determine what type of matter or what regions of the central nervous system we're looking at. So this is where we get the distinction of gray matter versus white matter. White matter, we're looking at mainly myelinated axons that are shift and rapidly transmitting information within gray matter. We're, we don't have any myelinated axons. We do also have a large amount of cell bodies and dendrites. Note that we can't have axons traveling through the grey matter, but those that are traveling through the gray matter are typically unmyelinated. Alright. And here we can also see the whole host of glial cells that are sitting within the central nervous system. Okay, so yet again, the law, central nervous. So let's talk about the peripheral nervous system. So the peripheral nervous system is outside in the gated community of that central nervous system. We're dealing with the, with the peripheral nervous system. We're not dealing with cerebral spinal fluid at all. Within the peripheral nervous system, we have specialized cells interact with blood supply, and then those will then feed and allow for material exchange with those cells of the peripheral nervous system. Note just as a basis for provoke at, when we're dealing with the peripheral nervous system, we can have a ganglia, which are clusters of cell bodies within the peripheral nervous system. These ganglia are generalized centers that have a shared functionality. Yet again, we're dealing with our act on, these are bundled together of on neurons. And these will form these peripheral nerves that travel to and from the central nervous system through the peripheral nervous system itself. Until when we're dealing with the peripheral nervous system, we're looking at really to Google culture, to neuroglial films. We have our satellite felt and are Schwann cells or satellite felt. Neither the Swiss army knife of, of the peripheral nervous system, the do everything through the surround fell body and footnotes from each other. And they regulate material exchange with blood supply. So they have a whole host of functions. The Schwann cells, these are a little more limited functionality, but are still very important because we're dealing with peripheral nervous system that is outside of that gated community of the central nervous system. Peripheral nervous system is exposed somewhat to the rest of the bottle. And because of this, we have to protect is very, very delicate neurons that are traveling through the peripheral nervous system. And if the swamp gov that will protect these neurons, okay. So they will surround some axons with myelin individually. But in general, the Schwann cells are wrapped around neuron, all neurons and, and protecting them. Within the peripheral nervous system. All neurons are, are interactive Schwann cells. How personalized that experience varies. So what do I mean by this? So here we're looking at the peripheral nervous system. So here we have a single neuron versus here we're dealing with multiple neurons, okay? So when we're dealing with a myelinated axon in the peripheral nervous system, this neuron is a VIP. This neuron traveling in a limousine, It has its very own Schwann cell aiding in rapid propagation of action potentials along attacks on versus our. The rest of the footnote. These neurons are taking the bus there, ride-sharing, okay? Are they interacting with by Schwann cells? Are they being protected by Schwann folks? Yes. But they don't have their own curated individually, a lot individualized button or helping out with all their functions. They just, they're all sharing this one Schwann cell that is protecting versus a. So this is the distinction between myelinated axon on the Peanut versus unmyelinated, both, in both cases within the PNS, our neurons are interacting with Schwann cells. But it's only in unmyelinated axons that we have individualized Schwann cells at which a single neuron versus unmyelinated axons, they're just sharing a single Schwann cells. Here's a big ol Schwab felt lapping and bundling a whole host of these axons. So by having this individualized care, this, this neuron could transmit information at a much more rapid pace than these guys. And that's really the distinction here. First for neurons in the peripheral nervous system that need to transfer information very rapidly, They're myelinated. Everybody else is unmyelinated, still associated with Schwann cells. But they're sharing national Schwann cell with everybody else versus this guy, the VIP. He's going to limo ride sharing or we're taking the bus, you're taking on taxes, that sort of thing. So let's talk about the anatomy of neurons themselves. There is a whole host of variation to this, which we'll get to a little bit later. But let's talk about some the basic structures of a neuron. So first and foremost, we have the cell body to this. Remember this is the living thought with very specialized cell at the very delicate fell, but it's still a living cell so it can maintain homeostasis, snap at them if the burden of guilt, a cage camp scenario. So with this, we have our dendrite branches, soma with these dendritic spine and D for the portion that receive stimuli, the stimuli, or it can be a whole host of things, could be chemicals. It can be electrical impulses. It can just be, I put, placed upon me that the dendritic spot. Then we have the axon. The axon is what transmit signal the action potential down at length. And then we have the axon terminals, which take that signal and transmit it to the next organ or tissue or cell silicon transmit information to another neuron. It could transmit this information to a whole host of different cells within the body. And remember that the neurons typically travel in one direction. So this inflammation that's traveling down, in this case we're looking at a motorneuron. But if this was say, an, a ferric pathway, neurons could be sending information to a particular region of the brave or particular region of the spinal cord itself. Also note within the vacuum terminals as yourself skeletal muscle. The main way that they interact with the next tissue is by the release of neurotransmitters. But that's not always the case. Sometimes there's direct connections where they will just continue to pass along that surgeon voltage. The change in voltage that, that change in membrane potential, that action potential. So looking, taking a slightly closer look at this, looking at the generalized structure again of a neuron. Here we have the neurofilaments div, give structure to the felt is very large. So these are our largest, largest solved within our bodies. So they need an extensive network. Of these neurofilaments, cytoskeleton to give them the shape and structure. Here at the axon hillock. This is a very important region because this is what connect the cell body to the axon itself. Also on a functional note it here at the axon hillock, where if there's enough of a signal to generate an action potential, the action potential will be generated at the axon hillock and then propagate down through the axon. It felt there's an actual platinum, which is the cytoplasm of the acts on its proper. And the interesting thing is that you have many of these. What they will have, what they will do is transmit as we'll dump the neurotransmitter inside the synaptic cleft with this next cell or tissue that they're interacting with. Did the SNR Transmit? What are these neurotransmitters? Comfort? Well, they are made in the soma and then brought down to the axon via exit plasmic transport. And then at the axon, then we have ethical that will dump these, those neurotransmitters into the synaptic cleft. So let's look at the variation in shape of axons. So there's a whole host of different types with different functionalities. And so with this we have our anoxic neurons. These are, we really don't see a polarity with these. And so we only see these within the central nervous system. And the special sense organs cannot really a whole bunch of different prophecies. We can't easily just gross, gross anatomy. Which ones are the dendrites and which ones are the axons, okay? We have a bipolar neuron. These have two distinct poles to them. That's what they're called bipolar. And so we have a dendritic side and an axon terminal side with the cell body in between at all. Ok. So these are typically food thing with facts and on hearing, these axons are not myelinated. Now we have our pseudo unipolar neurons. With these we see are dendrites. We have a cell body kind of in the middle, so these are little better act transmitting information. In comparison, the bipolar neurons relatively slower. And so with this, these may have myelin and these are censored sensor within the peripheral nervous system. And yet again, that full-bodied off to one side. Here we have our mulch, a multipolar. So when we think of a typical neuron, this is what we're thinking of, this multipolar neuron, where we have multiple dendrite, the whole theory, the dendrites coming off of that cell body. And we also have a Y branch of axon terminals. So single atom, multiple dendrites, which gives it that name, multi-polar. And yet again, this is our most common form of neuron within the central nervous system. So when we look at our neurons, we can classify them not only based on their shape, but what they're doing. What kind of information of a transmitting? Because all they are there, they're fancy wiring that's really all there other than transmitting information, transmitting an electrical current. And so we have pension and onthe mode and an internal ohms. So we're looking at our sensory neurons and a fair division. So these are bringing information into the central nervous system. So it is from the PNF to the cnf, a front. So with this, we can have them bringing in information from the somatic system, ok, so, and also from the viscera as well. Alright, so we can access information from skeletal muscle law from organs as a whole. So we have these interior receptors, these monitor internal organ activity focused. From the stomach, for example, we have external receptors. These are found typically up on the exterior of the body. These are sensing things like temperature, pressure. And then we also have these proper receptors that monitor body position and movement. These will bring information from the muscle spindle fibers to allow law for information about if that muscle is contracted or not. These will also bring in information from our joint capsules as well. Is that choice he activate or they're under strain because we're overexerting it, things of that nature. So looking at a motorneurons, These are sending information from the central nervous system or the peripheral nerves to our effectively which effect of Oregon is impacted? We'll classify that that subdivision. And so if that's when we're looking at a somatic nervous system, we are and ultimately impacting sculptor muscles, stimulating skeletal muscle, in some cases, relaxing it, but those are rare. With this, we have also our autonomic nervous system. Well, we're impacting all other types of tissues. So smooth muscle glands, cardiac muscle and adipose tissue to cigarettes. So with this sort of visceral motor neurons, and with this we also have our preganglionic and preganglionic and post-calving out ganglionic fibers that emanate from the ganglia. And the ganglia are just collections of cell bodies. This is, this isn't necessary with our visceral nervous system. Because our autonomic nervous system, because what this, what happens is because we're typically stimulating or impacting better said, we're sending information to a variety of different cell types within an organ or within a tissue. We need to put the finger up and a bunch of different way. And that's where these ganglia come into play. They are not always President, whether private. It's typically when we're splitting the signal to a whole host of different tissue touch. So that we have also interneurons. Interneurons are only found within the central nervous system, and these are situated between the motor and sensory neurons. These aid in the act as almost a secondary introversion center to some degree where they can kind of analyze sensory input and coordinate motor outputs from that sensory and put. These can be excitatory or inhibitory in nature. So let's talk about repair of the axon itself. So the thing to keep in mind is that in general, adult neurons do not divide once they are damaged. But they're done for you don't get a replacement neuron. But note that individual neurons can repair themselves. So if there is some degree of damage and the neurons survive that damage, it can repair itself. But there are some caveats to that. The thing to keep in mind, especially within the central nervous system, is that the ability of an individual neuron to repair itself is fairly limited, and this is due to the astrocytes themselves. The reason behind that the astrocytes are the Manning's for the, the neuron. They're watching over them, regulating what they're doing. And so what happens with these astrocytes will generate scar tissue that will limit how these axons will reap growth. So here we have an axon here, we have damaged right there, and it will start to regrow. The only sustained enough damage. I didn't outright died from that damage. What happens is that the reason the astrocytes limit axon regrowth is that these axons, if you think of them as there extending from the neuron, they're kind of like the root of the tree, okay? If you let just go anywhere it wants to go, it will interfere with the functionality of other neuro. And so these astrocytes will kind of keep these neurons or the axons from the neurons are damaged, growing in a particular order. Unfortunately, sometimes that results in them being a little smaller than they were, or sometimes they even heard them from regrowing back to their original five altogether. And they also do this physically through the formation of scar tissue, but also they'll secrete chemicals that will impede the act F13 growth. Because yet again, we don't want to act onto just emanate and go anywhere it wishes to. Because then that would literally call a short-circuit within the nervous system, which can have horrible ramifications depending upon which region the central nervous system we're talking about. When we talk about the nervous system, we have to talk about action potentials. Remember, this is how it rapidly transmit information at rest. And any cell, we have a slight negative charge within the felt. And this is primarily established, not solely a stash of primarily established by the present, the sodium potassium pumps. So remember, by using energy, by using ATP, we're pumping up three sodium and pumping n2 potassium against the concentration gradient due to this, because we're getting rid of three positive ions. And only, and taking two, we are establishing a net negative charge inside of the cell. There are a whole host of other things that will establish this as well. But this is one of the primary factors. This resting membrane potential due to the activity of the sodium-potassium pump, which is around minus 70, is the potential energy that can be used for rapid communication. And so when we deal with these excitable cells, which we've already talked about before. The third excited that felt can rapidly change your membrane potential due to a stimulus. Okay, they can have a flux from this change in membrane potential and the uv changes a member potential due to a stimulus are called graded potentials. Okay? And so these changes in membrane potential at an additive over space and time, and these are greater protections if these graded potentials are strong enough, they will reach the threshold value and cause an action potential. The reason that there's a threshold value is this is the voltage where the voltage sensitive gated protein, at that voltage, they will either slam open or slam shut, depending upon which. So we're looking at dependant upon where they are found within the bottle. And so what we have here are two scenarios. So here we're stimulating FL, Okay? So here we have a fell. We are measuring the voltage with them, the felt, and here we're stimulating it. Here we can hyperpolarize or depolarized. So hyperpolarize, make it even more negative. Depolarize make it more positive. Okay? And so here we can see the relative strength of the stimuli and the duration that we at fence towers document. Okay. And this was, And as an aside, this is kind of what interneurons do that kind of aid in and making sure that we really want to stimulate this region of the body. Are we going to allow it to, we're going to call that inhibitory stimuli to keep it from undergoing action potential. But anyhow, so inhibitory, we've become more and more negative. We get farther away from threshold with excitatory if it's strong enough and or of a long enough duration, we reach threshold and then we have an action potential. Yet again, an action potential is a rapid change in membrane potential over the surface of the cell. Will we think of these changes, the membrane potential that can be added single fight and they are added over time and space. And if we have enough of a change in membrane potential, graded potential at the axon hillock. When we reach threshold, then we develop an action potential travels down the axon. Ok? So this trend, this transfer of an actual principal travel of an action potential down an axon is called axon propagation. And this is where an axon will travel along the length of the axon. This is impacted by a whole host of things. Speed at which this signal, this wave of current change of voltage change I'll travels through is determined by the presence or absence of myelination and the thickness of the axon of a very thick axon will have a very fast transmission rate. But myelination will also allow for very fast transmission rate because the signal basically is allowed to we amplify itself at the nodes of Ranvier, okay? At each one of these points where the signal will hop, basically, leapfrog from, from opening to opening, will allow for amplification and propagation of that thing. And tough. And there's profit who's called saltatory conduction, just like you're playing leapfrog, the change involved, weigh the voltage shifts, jumps between each one of these open get, thereby strengthening and propagating in one direction. So the really cool thing about myelination is that it allows really, really small act thumbs to have very, very high conduction velocities and fill a very, very small axon with myelination can have the same velocity as a Act thought, an unmyelinated axon that dotted 25 times thicker, meaning that this myelination allow for smaller felt. Why do we want smaller, helpful, smaller shelter, beneficial in some instances because smaller, so energetically cheaper to maintain. It uses electron energy, uses lifts material, but also think about space thing. Just the nerves that are traveling theory your arm. Okay? If we had these massive, massive, solely massive unmyelinated axons traveling through, we'd have, we are nerves will be enormous. We'd have less space within our arms for other materials, so our arms would most likely be thicker, but that's just kind of speculation. But anyhow, this myelination allows for very, very rapid transmission of signals by a very, very thin small axons. So, and just to kind of remind you of this, we're dealing when we're talking about myelination in the context of the peripheral nervous system. Remember in the central nervous system, because we're dealing with that very protected. Scenario of cerebral spinal fluid bathing everything in the central nervous system. We do have unmyelinated backlog. Yet again, those are slower than myelinated axons. But in the peripheral nervous system, all neurons all act thumb are associated with Schwann cells. It's just our myelinated axons have their own personal Schwann cell. While, while our unmyelinated axons are sharing a swamp Schwann cell with other neurons. Okay? Lemme, they've taken the bus, okay. Or you know, you're taking your own Uber ride share. Still both are fast, but this one's much, much due to that individualized myelination that allows for, for saltatory conduction that Islam is much slower, relatively speaking. And feel the way that, that, that neuron transmits information to the next step is through that thin it. And so that synapse at the junction between a neuron and another cell. We can have different types of synapses, are the most typical are chemical synapses. These are one-way transmission. So here in this synaptic space, synaptic cleft, we can, the neuron will dump neurotransmitter. Those neurotransmitters will cause some type of change in membrane potential in that cell is receiving the signal. Electrical synapses leads and non circular. The distinction between electrical synapse, the chemical synapse. An electrical synapse is a chemical synapse have vesicles that will open and pour and dump neurotransmitter into the synaptic cleft, the space between the axon terminal and other cell or tissue where the electrical finance does not, that does not use the difficult. And so these electrical synapses, these are typically only found within the central nervous system or the peripheral nervous system. These can allow for signal transduction in either direction. And these are typically found between neurons. So they have gap junctions and they're just allowing that action potential to travel from one cell to another ad ions themselves. And look, remember, I'm being charged follicle as you move ions for causing changes voltage versus what these neurotransmitters here in this chemical synapses. If we dump enough neurotransmitter, then that will cause a large enough graded potential that will cause an action potential occur. Think back to what we saw with stimulating skeletal muscle. That's what's happening. In the case of stimulating skeletal muscle, we're dealing with a chemical synapse versus an electrical synapse. Let's talk about the different ways that neurons are arranged within the body to allow for different ways of transmitting information, whether this be a fair or you fair signals. So what we have what is called our neuronal pools. So this is the groups of organized neurons. And yet again, these are classified by how they are arranged and what type of in what, and how they relate information. That's well, first of all, looking at is divergence. And so this is information to multiple neurons from a single neuron. So one example of this, to say visual information to multiple brain centers. We feel that a lot with a lot of the special senses that we, that little bit of visual information goes to one part of the brain, but then it travels to other parts of the brain. Because with that when signal and that's the important thing to think about, about stimulus, especially stimulus coming to the central nervous system. The whole, yes, we can have a stimulus reaching that that spinal cord. So think back to withdrawal reflex. When we receive that initial pain from touching something hot, that stimulus will cause the withdrawal effects, but that stimulus will also travel up to higher centers of the brain where we have learning, where we have memory so that we have where we develop the memory that out fire, hop back. Okay, we don't touch fire because at birth. And then we develop half-wave and patterns of learning to prevent that behavior from happening again, when we can prevent that accidents happen dynamically. We learn quickly at baby youngsters that if you touch something hot Berg and that's through the stimulus going to other regions of the brain. And that's where the divergence comes into play. Github stimulus will go to theta withdrawal reflex, but that stimulus will then also go to higher portions of the brain for learning about pain and to perceive that pain in general. Then we have also convergence. So this is input to one neuron from multiple sources. And so that's an example of skeletal muscle. So those things sculpt the muscles that are, that are involved with say, withdrawal reflex. We can also voluntarily move those, sculpt them up and around. So there's multiple ways, multiple pathways for emulating that, that motor unit, and that's called a motor unit as well. Pyrococcus seems fairly, fairly easy to interpret. This is just a simple relate to say pain reception works this way where it just gets sent along from one neuron to another. We have our parallel proper thing. With this. A single stimulus elicits different responses in different types of effectors. And so for example, one way to think about this and say the barrel receptors of the stretch receptors which and the, the aorta. They bat information can go to multiple parts of the brain and then have different impact. Alright. We have reverberation. Reverberation is fairly rare and it's rare because in biology, positive feedback loops are fairly rare. So what a positive feedback loop, This is a system that AV, stimulus, avid at profit happened. It will increase the magnitude of that stimulus. Ok, so will rev it up. Okay, so when we're dealing with any type of positive feedback loop within the body, we're only building up to something had happened to them. Okay, so the whole host of things that occur this way, defecation is one of these. Knee pin can be thought of as one of the, you know, the stimulus to produce the food will build up, build up, build up until you need, and then we stop. Right? Parturition is one example of a reverberation loop. And if it can be stopped by an inhibitory loop through the presence of inter neurons will, or just that profit. Culminating at one way to think about death can be thought of as a reverberation or a positive feedback loop as a whole. And that all the things happen until morbidity, flip them till you die. But we've tried to think of it in a more positive chips. Okay, and then finally, let's talk about general language of dealing with nervous system as a whole. This is a really nice diagram that you'll look at because this kind of talks about some of the distinctions between language within the central nervous system and within the peripheral nervous system. As really important to take a look at this, because this will make future chapters within this section a little easier to understand when we talk about these distinctive collections of things. And that's really that we have particular language that involves the central nervous system and particular language that involves the peripheral nervous system. And this is all just because the central nervous system, because gated community kind of thing, super, super fancy. We have one set of terminology versus the peripheral nervous system. We just have a different set of terminology just to distinguish it. Until within the central nervous system have centers which are collections of cell bodies typically having the similar function. We have a nucleus. So anatomically the food they ate center with a distinct boundary which we could either dissect out or stay easily with a whole host of different compounds. And you will see these nuclei in the brain. We've talked about these a little bit before in prior chapters as well. And so in general, within the central nervous system, we see white matter as well. And these are bundles of axons that are oriented with an crack and columns, which we'll get to when we talk about the spinal cord and the peripheral nervous system. We have our, our ganglia and so ganglia and centers are the same thing. Just a collection of cell bodies in the central nervous system is the center, where in the peripheral nervous system it's a ganglion, had to think functionality, but it's just where they're located. And then when we had our nerves, our peripheral nervous system, these are just bundles of axons. And yet again, a whole host of different terms which we'll cover as we continue through these chapters. But really take a look at this nomenclature. Cuz it'll really help you through the remaining chapters in deflection. We'll review this chapter. Think about the distinction between the central nervous system and the peripheral nervous system will go into this in a lot more details, especially when we talk about the spinal cord itself. Think about the distinction between the neurons and glial cells. Distinct roles, the glial cells and how they support neurons. Think about also how a neuron undergoes an action potential and how use those action potentials for different types of reflex arcs are, Have a good day.

spinal cord

Now listen to this chapter. We're going to talk about the spinal cord. We'll talk about its role as an integration centered reflex arcs also talk about its role and its connection to the peripheral nervous system in relaying information to and from the central nervous system are, let's get started. So when we're looking at the spinal cord, we have to remember that it's part of the central nervous system. It works in tandem with the brain. It is a lot of ways an extension of the brain where the brain can exert conscious control over a lot of somatic musculature and also gain a lot of generalized sensor information from the body's hold. But the spinal cord can act as its own Integration Center on its own. So a lot of somatic reflexes are controlled by the spinal cord as well. Growth of the spinal cord, it terminates at around age four. And we can see here that conus Mitchell Eris and that inferior tip of the spinal cord that's work terminate at L1 or L2 in an adult. Note that we have a whole host of nerves emanating from that point. And this bundle of nerves is called the cauda cleanup or horses tail. And that's just is large extensions of nerves emanating from there. From that, the inferior tip of the spinal cord traveling through the dorsal hollow nerve tube, which is formed by the people arches. And it's this negative space. It's not just completely blank space, but there's a fair amount of negative space here. This allows us to say sample cerebral spinal fluid or, or administer an education straight to the central nervous system itself as a whole, which is greater with the spinal cord. We also have some distinct enlargements. These are enlarged regions that aid in controlling and dealing with the limbs. So we have a surgical for cervical enlargement right here dealing with upper limbs and we have the lumber sacrum enlargement, right? They're dealing with the lower limbs. The control of your lower limbs is emanates right there from your lower thoracic vertebrae. And so that's why, for instance or if there's any type of spinal cord damage that occurs even as high up and the thoracic. This will greatly impact the ability to walk in and relay information to and from the lakes themselves. Let's look at the general morphology of the spinal cord itself. And so here we have the dorsal posterior side. Here we have the anterior or ventral side. Note that the anterior side of intrasite always has this median fissure. Any which way we look at the spinal cord. There is a spinal segment, PR vertebrae. This is also present in the sacrament coccyx that remember, are fused vertebrae. And so with this, with any spinal segment, we have dorsal roots emanating from either side. We have dorsal root ganglia. We have a ventral root coming out and then the dorsal ventral root coalesce into a spinal nerve. So the spinal nerve contains mixed nerves that we'll have a turn at different fiber. So sending information from the spinal cord, but also bringing information to the spinal cord. So the spinal cord itself can act as Integration Center, or this information goes to the branch when we're sending efferent pathways from the spinal cord as the spinal cord itself acting as an effector or that information going to the brain itself. Also note that the general distribution of white matter, grey matter, varies a little bit as we travel down the spinal cord as well. So remember that the spinal cord is part of the central nervous system. Being part of the central nervous system. It's part of that gated community of a, of the central nervous system where we're protecting the stare very delicate tissue. The way we protect this delicate tissue is through the meninges. These coverings or extensions of the coverings that can be found within the brain, which we'll talk about there as well. And so what these managers are, these specialized membranes that do a whole host of things. They structurally support the spinal cord, they insulated and they provide a space for cerebral spinal fluid to travel within, within this cavity, within this coating on the spinal cord. So and so with this, we have the dura mater being the exterior portion of it. And then we have the pia mater being the most intimate on the direct surface, on the direct contact with the spinal cord itself. And then between the pia mater and the dura mater, We have the space or arachnoid space where we have basically this mesh. And it's this mesh which is the arachnoid mater, which the level between the PEA and the dura mater. So let's look at each one of these managers went by one. Let's first look at the dura mater. It's very, very tough as the outermost layer, it will stabilize a spinal cord in place and by stabilizing the spinal cord, replace it. It keeps the spinal cord from resting against any of the sides of the vertebral canal itself. Remember that the vertebral canal is that dorsal hollow nerve cord formed by the vertebral arches of each individual vertebrae. We have a whole host of Crane of attachment points that keep it in place neutrally. And so with this, we have also cranial sacral attachments that stabilize longitudinal axis. And this will create an additional with say, the Cox's ligament as well. This creates space between the actual dura mater and this ball and the vertebral and the vertebrae themselves. And this is the epidural space, soft. And so yet again, we also have the constitutive ligament where the dura mater will connect with the film terminal, like to keep the spinal cord as a whole suspended in space inside of that vertebral canal. Next we have the record matter, which is the middle meningeal layer. So this is the space between the pia mater and the dura mater. And as its name suggests, it's like spider webbing. And it's through this space, this layer that we have cerebral spinal fluid traveling through here. And so we have, it's, we have a subarachnoid space which has been, which is where the arachnoid mater will interact with the pia mater. And then it will also interact and attached to the dura mater as well. So we have this mesh that, this, that the cerebral spinal fluid travels through such kind of a connection point. But yet again, this, the establishment of the arachnoid mater allows the space to, to exist for cerebral spinal fluid to travel can flow freely while also suspending, basically suspending the pia mater within the hard casing dura mater. That's really the role of, of the arachnoid matter would look at it. It allows for, for the pia mater and the spinal cord that's trapped within to, to sit in within that dura mater in a neutral space. It's not resting up against a site because if it was resting up against the sidewalls, we would be able to transfer or flows through the spinal foot pass that point and we limit the capacity for exchange. Remember when we're dealing with the central nervous system, all the exchange of materials with these cells, with these tissues occurs via cerebral spinal fluid, maximized for as much as possible and to allow it to sit within the space and allow for flow around it. That's what this arachnoid mater and establishes. Ok. And so with this. The arachnoid trabeculae, which extend from the arachnoid to the outer layer. Pm matter a lot for anchoring between these layers. So let's look at the last layer, the pia mater. This is the deepest meningeal layer. This is what is firmly attached to the spinal cord. And also when we're looking at the brain, it's firmly attached to the brand as well. This is the layer where blood vessels are found. This is the layer where the cerebral spinal fluid will interact with vasculature and have exchange materials. With this. We also have these ridiculous ligaments and these aid and establishing this neutral space between the pia mater and the arachnoid mater and the dura mater kinda keeping everything in line. Keeping basically passive tension can sit within the space and not rest up against any one of these layers, cellae for maximum flow of material. So looking at this from a superior view, Note that you booked this something goofy here. Here's our, here's our ventral side, here's our dorsal posterior side. But note here we have our, so here we have vertebrae, here we have the epidural space. Here we have actual dura mater coding everything. There. We have the arachnoid mater and we can see that negative space that's generated that allows cerebral spinal fluid to travel flu and flow freely. Enveloping that he had the pia mater, enveloping the spinal cord itself. That pia mater is intimately associated with the spinal cord, with the actual nerve, nervous tissue itself. And we can see that the Dedekind ligament here, allowing it to hang passively and place, allowing that cerebral spinal fluid to flow over and through it. And yet again, as we connect to the nerves, we have this dura mater enveloping all this area which will terminate once you get to the base of each spinal nerve. So as we look a little closer to the composition of each spinal segment, we see that that it's a mixture of grey matter and white matter. In the center of the spinal segment we see this central canal, which is just a space that cerebral spinal fluid will travel through. Same thing with this, with this anterior median fissure. Basically just ways of increasing surface area, allowing for that cerebral spinal fluid to bathe the surfaces. So we're comparing gray matter versus white matter. Remember with our white matter, it's mainly axons with our gray matter. It is mainly some as the cell bodies of neurons. We also have glial cells living within this gray matter as well. Within the white matter, we're primarily looking at axons, mostly myelinated axons to increase their transmission rates and, or a single transmission rates. And so with this, when we're looking at a grey matter, we're looking at what we call horns for the somas or the orientation. As far as your organizational things. Within the white matter, we're looking at axons that are organized in tracks called columns. And yet again, these are, these are all located with outside of the gray matter. So let's look at the organization of the gray matter within the spinal cord. Ok. So the sum is the cell bodies of the neurons are organized into functional groups, and these are called nuclei, OK. And so with this, we have sensory nuclei and we have motor nuclei. Sensory nuclei transmits sensory information. They're receiving sensory information from elsewhere in the body. The motor nuclei are transmitting orders and factors equals eventually stimulate some type of effector organ. And so when we're comparing in general, dorsal versus ventral, so or, or posterior versus anterior. From the dorsal route, we have information coming in. On the ventral route, we have orders coming out. Okay. I'm and if we look at the distinction between our different corns, what we see is when we're complete, when we split down the middle, looking at posterior versus anterior, yet again, Dorsal versus ventral. We have sensory on the dorsal motor on the ventral. And so for art. And when we look a little closer at the horns themselves and we look at the dorsal horn. What we have is our somatic and visceral nuclei. Lateral horn right here, kind of just a small bump coming off. Here we see our visceral motor nuclei. And then anteriorly or anterior or ventral horn is our somatic motor nuclei. Note that we have very large amount of space here because we're dealing with stimulating a large amount of somatic tissue. This is one where we're primarily transferring orders to control skeletal muscle. When we think of controlling skeletal muscle, yes, some of these are tied to reflex arcs, but a lot of these are just conscious control. So things that will establish posture, establish walking rhythm right here all in that somatic region. Also, when we decide to wave at somebody, play video game, played instruments, whatever, walk, run. It's all here in this schematic region dependent upon which, which area we're looking at. Okay? So that's why the somatic region is fairly large in comparison to all the others. Then the KM measures. So we have the Posterior, Anterior Commissure and this is just where we have a linking between the ranking with tasks. That's really all they do is. And remember that this is a mirror between each side. So one sites dealing with right once that's dealing with the left of what's, what's happening in the body or control the body and bringing information in, sending information out. So dorsal bring information in, ventral sending orders out. When we look at the white matter, remember that the white matter is an extension of the gray matter. So while we have the soma and glial cells, neuroglial cells living here. What we primarily have are the white matter or all the axons that are emanating. So they fall account of the same organizational pattern. And so will we see we have these large columns which are subs, which is separated into small segments called tracks. And so when we're looking at the dorsal region, here, we're looking at sensory information travelling through the dorsal region. When we're looking at our motor tracts, primarily an anterior side or interior columns. These are manly motor tracts, descending tracts, relaying orders. These tracks and columns, these are primarily sending information up and down the spinal column to other regions of the spinal column, but also to the brain itself. Because most information that is generated by the spinal cord will eventually make its way to the brain. The brain that may not act upon that immediately, but that information gets relayed through there. Remember when we talked about withdrawal reflex from from file, touching something, pop the immediate action and stimuli of moving your hand out of the way after being bird is all handled by the spinal cord in that case. But still that sensory information, that pain, that, that, that sense of pain still mixed. What are the brain? They can learn about it. Touched the hot stuff again. Okay? And so with this, we also have, so we've got our posterior by column or dorsal, why call me of our lateral column, but we haven't interior call K. And yet again here we're looking at our, our motor, motor tracks and our sensory tracks running through so that relaying information up and down the spinal cord. So remember that the peripheral nervous system are the nerves that emanate from the central nervous system. The bulk of the nerves of the peripheral nervous system emanates from the spinal cord. There are 12 nerves that emanates from the brain, but the bulk of the nerves that emanate that form the peripheral nervous system emanate from the spinal cord. Each spinal segment has its own pair of spinal nerves totaling and 31. These will branch off further it as they expand throughout the body. So let's look at the peripheral nervous system really quickly here. So here we have a cross section of the spinal nerves wrapping it on the outermost layer we have epithelium, and the epithelium is continuation of the dura mater. Next we have these bundles of axons that are wrapped it with a parent area. And in these bundles where we have a fascicle. So this is a cluster of axons. Remember that when we're dealing with the peripheral nervous system, we only have satellite cells, Schwann cells. So the satellite cells are directly interacting with vasculature alive for material to, to, to exchange. And we have vasculature traveling through within the casing of the epithelium between these bundles of paradigm. And it's important for this, for these distinct membranes to present here because this allows for bundles of ions to interact with these nerves, allowing for action potentials to take place spin. Then finally, within each fascicle, We have the endometrium, the NW room. What it'll do, it'll either wrap individual axons or it will wrap multiple axon's, really what the engineer IAM is wrapping or schwann cells. So if we're dealing with a myelinated axon has its own personal Schwann cells wrapping it, then that Indonesia and we'll just wrap that one axon if we're dealing with an un-myelinated axons that are all sharing one a Schwann cell or sharing multiple Schwann cells, then that engineering will wrap those. That it's like a smaller sub bundle of the fascicle itself. So let's look at how the spinal nerves interact with are the spinal sections themselves. Remember that from this point onward is where we have our spinal nerves emanating from that spinal segment. Note that the action or functionality of the nerves is fluid. The nerve can both be a ferret. In effect, it's these root ganglion that are either Afinitor effort. So our dorsal root ganglion is always receiving information, while a ventral root is always, is always sending out effective, effective, or is always sending out orders. From most of our spinal nerves. We have a dorsal ramus and eventual Ramis. But for many of them, for all of our thoracic. Nerves and are a small percentage of our lumbar nerves. We have two additional branches. We have the spray, my commit a Kansas with wishes buff of white RAM is in a gray redness. And so this is where they're collectively joined. These aid in relaying extra information and extra signals to the viscera within the thoracic cavity and the abdominal cavity as well. And so here we're looking at just motor commands leaving the spinal cord as a whole. Remember here with our ventral root, we're sending commands outwards. So the efferent pathway versus the dorsal roots bringing sensory information and is an efferent pathway. Yet again are, or nerve starts from this point onward. Note, Graeme, I can both relay information, relate orders are carrying sensory information. In words. When we're dealing with a RAM, I come into conscious. They're associated with a sympathetic ganglia, which is a small division of the sympathetic nervous system. And it's the ganglion that deals with information and orders coming to and from the viscerally. And where these are located, we're dealing with a larger amount of visceral, therefore, necessitating the small kind of processing spaces if you want to think of it that way to aided all this information that's coming and think about all this or that's just in the abdominal cavity above. We have the stomach, we have all those other GI organs. You have all the vasculature, it, all this information coming in and out of those areas and these ganglion help in, in, in sorting that information out, whether be sensory information going to the spinal cord and maybe ultimately to the brain, or the factors for visceral reflex arcs to aid and controlling what's happening within the thoracic cavity, but also the abdominal cavity as well. One neat thing about the spread of spinal nerves and how they can relay information to and from different regions is that we have dermatomes. And these are regions of skin that are innervated by specific spinal nerves. And so one very rapid way that we can assess if there's any type of spinal damage is by just literally using a small set of pins to regions of the skin. And if there's sensation within these distinct regions of the skin, we know that that state spinal nerve is stuff functionally, properly, which is really, really cool and fast way of determining if there's any type of spinal damaged after some type of injury. And so now that we've talked about the functionality of the spinal cord a bit, we're going to talk about just spits organization as a whole. Especially we're dealing with the nerves that are emanating from it. And so emanating from the spinal cord, we have these four large groupings of nerves, which are these plexuses. So this is an interwoven network of nerves. And these are the main networks of nerves that emanate from the spinal cord being. But the bulk of the peripheral nervous system. Remember, this does not take into consideration to cranial nerves that are emanating from the brain. This is just considering the nerves emanating from the spinal cord. Now note, it's a massive amount of nerves, but these are primarily involved with somatic reflexes are somatic control or sensory input from the body. So lot of appropriate reception also gets related to this through these nerves as well. So we have our cervical plexus are brachial, lumbar and sacral. So looking at the server cervical plexus, plexus itself. So that's just showing how we have this branching off of these peripheral nerves. Note this is the only place within the cervical plexus where we do have a little bit of cross talk with some of the cranial nerve, the hypoglossal nerve, accessory nerve that worry about that too much. Just know that some of these nerves of the cervical plexus aid and bringing information to the cranial nerves. Remember that the cranial nerves emanate from the brain directly. They bypasses spinal cord completely. And then with within the cervical plexus, we also have the cutaneous muscular branches. That cutaneous branch will innovate the head, neck, and chest. So especially upper chest itself. So here we can see the brachial plexus. The interesting thing about the brachial plexus is the bulk of it emanates from the lower cervical vertebrae. This is why if somebody has spine damage, especially say, in the middle of the thoracic cavity, they still typically retain functionality of their upper limbs because that control or that are those HER in Ethernet pathways actually originate in the lower cervical vertebrae, not in the thoracic vertebrae. So here we can just see this branching pattern of, of these nerves as they emanate from the spinal cord itself. Here you see the lumbar plexus, where we have branching from the very last dress vertebrate and all of the lumbar vertebrae. Here we can see the sacral plexus. The really interesting thing of note is all these nerves emanate from the sacral foramen, which will then coalesce into when very large cyatic nerve there will travel down the length of the lower appendage. Here we can see more detail branching of the upper nerves of the upper pendant. And here we can see a branching of the lower advantage. And so since we've talked about the spinal cord itself, let's talk again about reflex arcs. Remember the reflex arc is an immediate involuntary motor response to stimuli. The bulk of our somatic reflex arcs are housed within the spinal cord or something. And so yet again, we can see the neural wiring of it. So we have our effort and our Ethernet pathway, which starts at a sensory separate, ends at a peripheral effector. Alright? And yet again, in the case of a spinal reflex, spinal reflex or a motor somatic reflex, we have the dorsal route handling the efferent pathway in the ventral route handling the effect pathway. Okay. So dorsal, sensory ventral is effective. Throughout the semester we've talked about different types of reflex arcs, but we've primarily talked about somatic and visceral, which are both innate reflex arcs. We can kind of expand this conversation a little bit more and talk about wired reflex arcs as well. Note that we focused in on an ornate ones because this is, these are the ones that keep us alive day-to-day are acquired ones alert R and R, just a byproduct of the're ontogeny or what profession you have, or what activities you want to engage in. Alright? And so we're looking at classifying reflex based on development. We have our innate, which are the ones that we've talked about up until this point. And when we typically think of a reflux R, this is what we're truly talking about. We're really talking about these innate genetic ones that are found throughout any person in the world, assuming they are quote, unquote, anatomically normal, quote-unquote physiologically normal. Acquire. These are learn reflexes. This is muscle memory, okay? These are solely somatic in nature. And this is due to repetition, training and practice. Learning an instrument, playing a sport. They either playing a video game, any type of repetitive motion that you can undergo without much thought, or almost in some cases, no thought or very little thought. This is all the quiet where you have a pre-programmed set of, of, of activities that occur after that initial stimulus. Ok, whether it be to jump on a platform, from a platform if you're a swimmer, to how to control the muscles in your hand to shoot him. Okay, that's one thing. So when we're looking at these distinct classification of reflections, we can also look at where that information is processed, what acts as the integration sector, whether it's the spinal cord or the brain that's acting as the integration center. And yet again, we can also think of the nature of the resulting motor response being, we can either look at our somatic reflexes are visceral reflex is, yet again, we're dealing with acquired reflex is learned reflexes are all somatic. Alright? And then also we can look at the complexity of the type of neural circuit involved. So many reflexes are monosynaptic. So there's one very simple loop. Some are polysynaptic where we have multiple loops of, of neurons ellipse of nerves involved with this. So we're comparing monosynaptic first postsynaptic. It's really mainly about the effective. If we have a single neuron that's being stimulated as effective, then we have a monosynaptic reflex arc. But when they have polysynaptic, This is when multiple neurons are activated sending effectors out. So say for establishing posture, there would be an example of a monosynaptic reflex are versus our classic withdrawal reflex that we touch something hot. That in that we're, we're activating multiple bundles of muscle fibers to have on hand away. So we're comparing spinal to cranial reflex arcs. Remember that our spinal reflex arcs are overwhelmingly somatic and interests or they're controlling skeletal muscle. A lot of these reflexes deal with posture, establishing posture, mechanic posture, but also in dealing with rhythmicity of walking to some degree aiding in the establishment of that rhythmicity walking. So what are the things that are spinal reflexes controls is that the rhythm or the cadence of our walk alterations to the cables that are walk that's controlled by the brain because that tells us to slow down or speed up or say, all true footfall. But if we're just walking in a very set pace that is controlled by a spinal reflex. So the stretch reflex is how that works and where the this reflex arcs census stretching of an intended muscle group and that causes through this stretch reflex for that muscle group that sense to stretch too crowded to then immediately afterwards sensed flexion of the limb. A couple will automatically cause extension of the limb again, thereby allowing setting up for rhythmicity of walking. Alright? Yet again, these can also be used for establishing or maintaining posture as well. So the SWOT a's and keeping you from just flopping out of your seat. Since we'll review this chapter, think about the distinction between white versus gray matter. Think about the distinction between our dorsal versus eventual warrants. Then also thinking about the classifications of the different reflex arcs and also the different types of been energies are,