Nervous System
Axons________ and dendrites _______
axon sends signals and dendrites receive signals.
Dentrites are.....
- Dentrites are the processes of the neuron that receive signals from the previous neuron. - A given neuron will normally have many dendrites to receive various types of input signals from varous other neurons. - Dentrites are usually short, multiple, tapering, and highly branched.
The cerebrum....
- The cerebrum is the largest part of the brain (80% of our brain). - It has two hemispheres that are connected by a deep bridge of nerve fibers called the corpus callosum. -The cerebrum is divided into two halves: the right and left hemispheres. They are joined by a bundle of fibers called the corpus callosum that transmits messages from one side to the other. -Each hemisphere controls the opposite side of the body. If a stroke occurs on the right side of the brain, your left arm or leg may be weak or paralyzed.
The somatic nervous system controls:
- voluntary responses -responsible for relaying the sensory and motor information between the outside environment and the CNS - Innervate Outer Sections of the Body (skin and skeletal muscles) - Any muscle movement or voluntary motor output uses the somatic nervous system
The axon is.....
-The axon is the process of the neuron that sends signals to the axon terminal, where the signal is then passed onto the next neuron -The axon is a single, long, thin process from the neuron cell body with axoplasm and axolemma. Axoplasm is the cytoplasm within the axon of a neuron (nerve cell). The axolemma is the cell membrane surrounding an axon. -What the axon basically does is it conducts impulses from the cell body to another neuron, muscle fiber, or gland cell. -Axon collaterals are the side branches along the length of the axon.
The cortex.....
-The surface of the cerebrum is called the cortex. It has a folded appearance with hills and valleys. The cortex contains 16 billion neurons (the cerebellum has 70 billion = 86 billion total) that are arranged in specific layers. -The Cortex can be divided into the gray matter and the white matter.
In chemical gradient....
1) The chemical gradient, or difference in solute concentration across a membrane, When there are unequal concentrations of an ion across a permeable membrane, the ion will move across the membrane from the area of higher concentration to the area of lower concentration through simple diffusion.
Macroglial cells can be further broken down into subtypes. They are......
1. Astrocytes 2. Satellite Cells 3. Schwann Cells 4. Oligodentrocytes 5. Ependymal Cells 6. Choroid Plexus
What are the Important Types of Sensory (Afferent) Neurons....
1. Mechanoreceptors 2. Nociceptors 3. Thermoreceptors 4. Chemoreceptors 5. Electromagnetic (light) receptors
Step 1 of to create an action Potential to stimulate a neuron to send a signal to another neuron....
1. Neuron Starts at a -70 mV Resting Potential and This Resting Potential is MAINTAINED by the Na+/K+ ATPase Pump At resting membrane potential, sodium potassium pumps (Na+/K+ ATPase) use ATP to pump three Na+ ions out of the cell and two K+ ions into the cell. Thus, the inside of the cell is more negative than the outside, giving it a negative resting membrane potential. The neuron starts off at its resting potential, its unstimulated state. This resting potential for a typical neuron is around -70 mV . This resting potential is maintained by Na+/K+ ATPases, pumps along the membrane that actively transport ions so that Na+ is on the outside of the neuron and K+ is on the inside of the neuron. The Na+/K+ ATPase exchanges three Na+ out of the neuron for two K+ into the neuron, and consumes one ATP molecule. The ATP is hydrolyzed to power this exchange, as both Na+ and K+ are pumped against their concentration gradient, through the process of primary active transport. Since more positive ions are being pumped out of the neural cell than are being pumped in, this makes the inside of the neuron more negative, and this action maintains the negative resting membrane potential-it does NOT encourage an action potential.
The three classes of neurons involved in the somatic nervous system are....
1. Sensory (Afferent) 2. Interneuron 3. Motor (Efferent)
Even though the basic components between parasympathetic and sympathetic nervous systems are essentially the same, their physical structures turn out to be different in a few important ways. And those differences can help explain why they act like the foils that they are. The two competing systems differ chiefly in:
1. Sites of origin of neurons from the central nervous system 2. Location of their ganglia 3. Relative lengths of their fiber 4. Neurotransmitter used
To pack more gray matter into a small amount of space in our skulls......
1. To pack more gray matter into a small amount of space in our skulls, the cortex must be wrinkled. 6 2. The surface is marked with ridges called convolutions or gyri, which are separated by groups.
In Electrical gradient.....
2) electrical gradient, or difference in charge across a membrane. Ions also carry an electric charge that forms an electric potential across a membrane. If there is an unequal distribution of charges across the membrane, then the difference in electric potential generates a force that drives ion diffusion until the charges are balanced on both sides of the membrane.
A ganglion is
A ganglion is a cluster of nerve cell bodies in the peripheral nervous system (i.e., a cluster of the nerve bodies that are not in the spinal cord or brain). The ganglion is where the preganglionic nerve axon synapses with the cell bodies of the postganglionic nerves.
The Parasympathetic Vagus Nerve .....
A major nerve of the PNS is the vagus nerve. The parasympathetic vagus nerve extends from the medulla oblongata and innervates parts of the heart, lungs, stomach, intestines, and liver to regulate these passive actions. Here are some examples of rest and digest reactions: 1 relaxation of muscles 2 decrease in heart rate 3 maintenance of homeostasis 4 Increase in gastrointestinal activity- this hits at the "digest" part of "rest and digest". Increase in gastrointestinal activity (such as peristalsis, the concentric, wave-like contraction of the GI tract) increases digestion.
The major nerve of the parasympathetic nervous system is.....
A major nerve of the parasympathetic nervous system is the vagus nerve which comes out of the medulla oblongata
A neuron decides whether to fire an action potential or not based on........
A neuron decides whether to fire an action potential or not based on the summation (or the adding up) of graded potentials and whether the summation is higher or lower than the threshold potential (-55mV) the threshold potential is the minimum potential needed to trigger an action potential which is -55 mV
ATPase is....
ATPase is an enzyme. ATPase breaks down ATP into ADP and a free phosphate ion, releasing energy. Just like lipase breaks down lipid and lactase breaks down lactose, the same way ATPase breaks down ATP. ATP is the energy currency of the body. But without the enzyme ATPase energy cannot be extracted out of the ATP.
The Arachnoid Mater....
Arachnoid Mater: Midde layer..no blood vessels, a thin delicate layer. It's a thin, web-like membrane that covers the entire brain. The arachnoid is made of elastic tissue.
Astrocytes
Astrocytes are the most abundant type of glial cell. Astrocytes= CNS They help: 1. provide blood supply to CNS neurons 2. recycle neurotransmitters 3. Maintain proper ion levels. 4. Form the very important blood-brain-barrier.
How is the resting membrane potential maintained? How is the solute concentration maintained?
At resting membrane potential, sodium potassium pumps (Na+/K+ ATPase) use ATP to pump three Na+ ions out of the cell and two K+ ions into the cell. Thus, the inside of the cell is more negative than the outside, giving it a negative resting membrane potential. This also means that inside of the cells the concentration of sodium is lower than the outside since 3 Na+ ions are being pumped out and the concentraion of potassium is higher inside than outside since 2 K+ ions are being pumped in. This is known as the difference in solute concentration.
The Sensory (Afferent) neurons are.....
Sensory (afferent): closely associated with receptor cells; responds to external stimuli or internal conditions and relays them to the brain and spinal cord.
The three layers of the meninges are....
The three layers are the Dura mater, Arachnoid, and Pia mater. Mnemonic for the order of outermost to innermost meninges: DAP
refractory period is......
The time period in which the neuron is hyperpolarized and difficult to depolarize again to make more positive is called the refractory period. Refractory periods can be absolute or relative.
the action potential will occur when.......
the action potential will occur when Na+ gated channels are open and allows Na+ to flood into the neuron, because then it makes the membrane potential positive and allows it to depolarize the membrane and help it ultimately reach a membrane potential of around +30 mV which is when an action potential will occur and finally send a signal from one neuron down to another. .
The main function of oligodendrocytes and schwann cells is.......
the main function of oligodendrocytes is to provide support and insulation to axons in the central nervous system of some vertebrates. This is equivalent to the function performed by Schwann cells in the peripheral nervous system. Oligodendrocytes do this by creating a myelin sheath, which is 80% lipid and 20% protein.
threshold potential is......
threshold potential (the minimum potential needed to trigger an action potential).
A synapse is....
synapse....where two neurons communicate in one direction
Neurotransmitters are released when.....
Action potentials are propagated across the length of the axon until it reaches the axon terminal. The axon terminal holds neurotransmitters (chemical messengers) that are released into the synapse and received by another neuron. Remember axon sends signals and dendrites receive signals. The synapse (or synaptic cleft) is the space between the two neurons. The presynaptic neuron is the neuron that releases neurotransmitters into a given synapse. The postsynaptic neuron is the one that receives the neurotransmitters in the synapse by receptors.
When an action potential reaches the end of the presynaptic axon......
Action potentials travel down the axon and reaches the end of the presynaptic axon and reach the axon terminal, which contains voltage gated calcium channels. These voltage gated channels respond to the action potentials and open causing Ca2+ ions to flow into the presynaptic neuron. This Ca2+ inflow triggers synaptic vesicles to fuse with the membrane, and via exocytosis they release the neurotransmitters they contain into the synapse/synaptic cleft (gap between neurons). These neurotransmitters travel across the synapse and bind to receptors on the postsynaptic neuron. Here, they trigger an appropriate response depending on the type of neurotransmitter released. Each neurotransmitter has a different function, they can inhibit or excite different function throughout the whole body.
How are Sensory (Afferent) and Motor (Efferent) neurons related......
Afferent neurons are sensory neurons that carry nerve impulses from sensory stimuli towards the central nervous system and brain, while efferent neurons are motor neurons that carry neural impulses away from the central nervous system and towards muscles to cause movement.
An action potential occurs when__________
An action potential occurs when a neuron sends information down an axon, away from the cell body. Neuroscientists use other words, such as "spike" or an "impulse" for the action potential.
An electrochemical gradient is....it consists of which two parts.......
An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts: 1) The chemical gradient, or difference in solute concentration across a membrane, 2) electrical gradient, or difference in charge across a membrane.
Location of their Ganglia
Another difference between these two foils? Their ganglia. Unlike your sensory or motor neurons, where a single axon can reach all the way from your spinal cord to whatever muscle or touch receptor it works with**, both parts of your autonomic system require two neurons in order to work. And those two neurons meet in ganglia - clusters of neuron cell bodies that house millions of synapses. But where these ganglia appear relate to their function, and which division of the autonomic system they're serving**. Sympathetic ganglia are found closer to the spinal cord, because in those fight-or-flight moments of high excitement or activity, they need to be able to send a single message far and wide like the Bat Signal. This way, excitatory signals traveling into a ganglion near the spine can trigger action potentials in a whole bunch of other neurons that lead to many different effectors, like the heart, lungs, and stomach, and adrenal glands. By contrast, most parasympathetic ganglia are found way out from the spine, near or even inside their effector organs. Because this system is responsible for taking care of particular functions only when you have the time and energy to do it-like digesting food or excreting waste- it uses more specific, strategic signals.
Relative lengths of their fibers
Because the ganglia of these two divisions appear in different places in your body, it makes sense that their neurons themselves have slightly different forms, namely the length of their axons. Now ganglia can be kind of complex, it actually comes from the Greek word for "a knot in a string" - so when dealing with neurons around these structures, we look at the fibers before they run into the ganglion, as well as after they come out of it. Understandably enough, the axon lengths of the neurons before the ganglion are called the preganglionic fibers, and the ones coming out are postganglionic.
Your brain and spinal cord are made of fragile jelly-like nervous tissue that is extremely susceptible to injury....your body protects them by.....
Both your spinal cord and brain are made of fragile, jelly-like nervous tissue that is extremely susceptible to injury. So all that goo is well-protected by the bones of your vertebrae and cranium, as well as membrane layers, or meninges, before being bathed in a cushy water bed of clear cerebrospinal fluid. This fluid actually allows your brain to float somewhat in your skull, reducing its weight and letting it slosh around while you and your head are free to move.
What is the point of the nodes of ranvier?
By promoting ion exchange at the nodes of Ranvier (gaps), the action potential jumps from one node to the next- and this is much faster than having ion-exchange down the entire length of the axon. This 'jumping' is known as saltatory propagation ('saltare' means jump)
What two factors effect the speed of an action potential propogation?
By promoting ion exchange at the nodes of Ranvier (gaps), the action potential jumps from one node to the next- and this is much faster than having ion-exchange down the entire length of the axon. This 'jumping' is known as saltatory propagation ('saltare' means jump) Myelination and the diameter of the axon are both factors that affect the speed of the action potential propagation. These two variables depend on a quicker or slower propagation rate.
The parasympathetic nervous system....
CALM - rest and digest response system - restores the body to a calm and restful state
The sympathetic nervous system....
CRAZY - fight or flight response system - causes general alertness and excitement - body's way of responding to a perceived threat
The Cerebrospinal Fluid (CSF) is.....
Cerebrospinal fluid (CSF) is a clear fluid that flows in and around the hollow spaces of the brain and spinal cord, and between two of the meninges (the thin layers of tissue that cover and protect the brain and spinal cord). It helps provide a mechanical barrier against shock, supports the brain and provides lubrication between surrounding bones, the brain and spinal cord. When an individual suffers a head injury, the fluid acts as a cushion, dulling the force by distributing its impact. The fluid helps to maintain pressure within the cranium at a constant level. The CSF is created by the Choroid Plexus
The three important parts of the brain are...
Cerebrum, Cortex, and Deep Structures
Chemical neurotransmission is....
Chemical neurotransmission is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron) and bind to and react with the receptors on the dendrites of another neuron (the postsynaptic neuron).
Chemoreceptors....
Chemoreceptors respond to chemical stimuli
Chloride channels are another type of Inhibitory postsynaptic Potentials in which......
Chloride Channels— IPSP: Other IPSPs can cause chloride channels to open, allowing negatively charged Cl- influx, into the neuron, which also makes its membrane potential more negative and makes it harder to bring the membrane potential to the threshold.
Dental injection prevents action potential from occurring...how does this work?
Dental injection prevents action potentials from occurring by blocking Na+ channels. When a dentist administers an anesthetic such as Novocain, he or she essentially blocks the sodium gates in the neuronal membrane. Because the sodium gates do not open, an action potential cannot occur. Now, without an action potential, nerve impulse transmission to the pain centers in the brain does not occur.
The Dura Mater.....
Dura Mater: Outermost layer..many nerves and blood vessels..tough and fibrous
Relative Refractory Period is........
During a relative refractory period, a very strong and powerful stimulus would be needed to elicit an action potential. This is when the voltage gated sodium channels are no longer inactivated, but the neuron is still hyperpolarized.
Absolute Refractory Period is......
During an absolute refractory period, a second stimulus cannot generate another action potential no matter how powerful it is because the voltage gated sodium channels are inactivated, so Na+ ions cannot inflow into the neuron to make it pass the threshold value, hence no action potential can be fired. It is absolutely going to refuse any reaction to a stimulus until the membrane reestablishes at resting potential and the voltage gated sodium channel works again to allow Na+ influx into cell to make more positive.
EPSPs and IPSPs are referred to as _____________
EPSPs and IPSPs are referred to as graded potentials.
Electromagnetic (light) receptors....
Electromagnetic (light) receptors respond to light, electricity, and magnetic stimuli
Ependymal cells are.....
Ependymal cells: 1. Ependymal cells produce cerebrospinal fluid (CSF), which cushions the CNS. 2. Functions as a type of neuronal support cell. 3. It forms the epithelial lining of the CSF in the ventricles of the brain and the central canal of the spinal cord 4. circulate the CSF in a sweeping motion using their ciliary projections.
Excitatory postsynaptic Potentials (EPSPs) are......
Excitatory postsynaptic Potentials (EPSPs) are generated by excitatory neurotransmitters. Excitatory neurotransmitters cause Na+ ion gates to open, which results in a Na+ inflow. This causes the neuron to become more depolarized (more positive) and bring the membrane potential close to the threshold value (from -70 mV to -55 mV ultimately to +30 mV) at which the neuron will fire an action potential.
Glial cells are....
Glial cells are the non-neuronal cells in the nervous system that nourish, support, and protect the neurons by making sure the conditions are perfect for neuronal health.
Graded potentials are
Graded Potentials are Short-lived, localized changes in membrane potential Refers to synaptic or receptor potentials that can vary in amplitude and direction. Graded potentials can be depolarizing or hyperpolarizing and do not have a threshold Graded potentials can vary in magnitude (size of depolarization/hyperpolarization).
Graded potentials are generated by the.......
Graded potentials are generated by the binding of neurotransmitters to receptors on dendrites. This occurs on the postsynaptic neuron releasing the neurotransmitters
Graded potentials summate at the.....
Graded potentials summate at the axon hillock.
Sensory (Afferent) VS. Motor (Efferent)
Here is how to remember the difference between afferent and efferent neurons. A comes before E in the alphabet. The stimulus must come before the response. The afferent neuron must bring the stimulus to the CNS before the efferent neuron can bring the response from the CNS.
Step 3 to create an action Potential to stimulate a neuron to send a signal to another neuron....
If the stimulus is strong enough, the neuron will depolarize past the threshold potential (the minimum potential needed to trigger an action potential). The threshold potential in a typical neuron is around -55 mV. When the neuron is depolarized to -55 mV, the neuron will open even more Na+ gated channels to let even more Na+ to flood into the neuron, making the potential even more positive. This completely depolarizes the membrane and allows it to ultimately reach a membrane potential of around +30 mV (called an action potential).
If the sum of the EPSPs and IPSPs is higher (more positive) than the threshold potential then.....
If the sum of the EPSPs and IPSPs is higher (more positive) than the threshold potential which is -55 mV, an action potential will fire down the axon (headed towards the axon terminal).
If the sum of the EPSPs and IPSPs is lower (more negative) than the threshold potential, an action potential will .....
If the sum of the EPSPs and IPSPs is lower (more negative) than the threshold potential, an action potential will not fire. In other words, nothing will happen. A graded potential that does not result in an action potential has no refractory period.
If you increase the stimulus in order to create an action potential, will the speed along the axon change? What will increase the speed along the axon?
If you increase the stimulus, we generate more action potentials but the speed and amplitude (height) of the action potential will not change by increasing the stimulus. speed is constant along the axon When a neuron is stimulated, it depolarizes (membrane potential becomes more positive). This allows for the action potential to increase but the speed is constant, so increasing the stimulus will only allow a greater degree of depolarization. The only thing that will increase the speed of the action potential is 1) Myelination: having a myelin sheath will also allow for fast action potential generation along the axon. Myelin insulated the axon's membrane, and ion flow is restricted to the nodes of Ranvier. The impulse jumps from node to node by saltatory conduction which is faster than having the impulse flow through the full length of the axon. 2) The diameter of the axon: The larger the diameter, the faster the impulse can move along the axon. n. These two variables depend on a quicker or slower propagation rate.
In either case of refractory period, the neuron.....
In either case of refractory period, the neuron will eventually re-establish its resting potential (-70mV) by the Na+/K+ ATPases, and the cycle starts over again with another stimulus.
Inflammation of the meninges is called______ and involves the_______
Inflammation of the meninges is called Meningitis and can be bacterial or viral. It usually will involve the arachnoid and pia maters.
Inhibitory postsynaptic Potentials (IPSPs) are.......
Inhibitory postsynaptic Potentials (IPSPs) are generated by inhibitory neurotransmitters. Inhibitory neurotransmitters cause K+ ion gates to open, which results in a K+ outflow. This causes the cell to become more hyperpolarized (more negative) and makes it harder to bring the membrane potential to the threshold value (+30 mV which causes an action potential). This is done to inhibit a action potential from firing.
Interneurons are
Interneurons are association neurons They are located between sensory and motor neuron; integrates sensory input and motor output
Just because you have graded potentials does not mean ......
Just because you have graded potentials does not mean you will fire an action potential, it just means you have some kind of potential, either negative or positive and there's no clear indication it will cause a depolarization (help create action potential) or hyperpolarization (help inhibit an action potential from firing) .
Mechanoreceptors....
Mechanoreceptors respond to a mechanical stimuli (such as touch and sound)
The meninges are...
Meninges are the three membranous layers that surround the brain and spinal cord. They function to protect the central nervous system, support blood vessels and enclose a cavity filled with CSF.
There are two categories of glial cells.....
Microglia and macroglia
Microglial cells are....
Microglial cells are the defenders of the central nervous system. They are specialized macrophages which protect the central nervous system.
Most _______ have both sensory and motor fibers and are called _________
Most nerves have both sensory and motor fibers and are called mixed nerves
Motor (Efferent) neurons are...
Motor (efferent): carry impuses out from the brain or spinal cord to effectors such as muscles or glands
Myelin sheaths ___________. The action potential ion exchanges process can only occur __________
Myelin sheath insulates the axon from undergoing ion exchange, and the action potential ion exchange process can only occur where there are gaps in between myelin. These gaps (non-myelinated regions) are known as nodes of Ranvier.
Myelin sheaths on axons are....
Myelin sheath is the fatty insulation of the axon and helps the action potential to propagate faster down the neuron.
Myelin sheaths are formed by ________ in the central nervous system and by __________ are formed by the peripheral nervous sytem.
Myelin sheaths are formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.
Nerve Growth Factors....
Nerve growth factors are proteins that regulate cell behavior by binding with receptors that can cause a biochemical cascade. Nerve growth factor is a neurotrophic factor and neuropeptide primarily involved in the regulation of growth, maintenance, proliferation, and survival of certain target neurons.
How do signals pass between axons and dendrites?
Neurons are lined up head to tail or dendrite to axon The signal is passed down from the soma to the axon. From the axon, the signal goes and hits the axon terminal which connects to the dendrites of the next neuron. The dendrites hence receive the signal in this way. Axon sends signals and dendrites receive signals. A given neuron receives an input signal from the previous neuron through its dendrites, relays the signal down its axon, and then sends an output signal to the next neuron through its axon terminals.
How do neurons send signals to each other?
Neurons send signals to each other via changes in their membrane potential, a voltage determined by the different concentrations of different ions across the membrane.
Neurotransmitters are....
Neurotransmiters are chemical messengers.
Nociceptors....
Nociceptors respond to painful stimuli
Too much of a good thing can often get ugly. While your cerebral spinal fluid protects your brain and spinal cord....if too much of it exisits then..
Of course too much of a good thing can often get ugly. Usually that cerebrospinal fluid is produced and kept circulating through and around the brain at a steady rate, but if say, a tumor gets in the way, that fluid can accumulate putting dangerous pressure on the brain in a potentially deadly condition called hydrocephalus, which literally translates to "water on the brain", high intracerebral pressure. But even with all that extra protection, your brain is still vulnerable and these vulnerabilities can be incredibly specific because your brain is divided into specialized regions that may or may not interact with each other to produce a given action.
Oligodendrocytes are ......
Oligodendrocytes are cells that form the insulating myelin sheath in the central nervous system.
Step 4 to create an action Potential to stimulate a neuron to send a signal to another neuron....
Once the membrane potential reaches its max potential, the neuron will repolarize, meaning the membrane potential goes back to becoming more negative. This is because by the time the neuron reaches its max potential, K+ gated channels open up, causing K+ outflow out of the neuron. Because positive ions flow out, the membrane potential becomes less positive
The Pia Mater....
Pia mater: Innermost layer, very vascular and intimately attached to the brain and spinal cord. It hugs the surface of the brain following its folds and grooves. The pia mater has many blood vessels that reach deep into the brain.
Polarization = ____________ Depolarization = ______________ Repolarization=_________
Polarization = Inside negative Depolarization = Inside now becomes positive Repolarization= Inside negative again
Preganglionic nerves come from......and postganglionic nerves are the nerves that come after
Preganglionic nerves come from the central nervous system and synapse with the ganglion. They are the nerves that are before the ganglion; i.e., preganglionic. So, postganglionic nerves are the nerves that come after the ganglion; i.e., postganglionic.
Primary active transport vs secondary active transport.....
Primary active transport, the energy is derived directly from the breakdown of ATP, it directly uses energy to transport molecules across a membrane. In secondary active transport, the energy is derived secondarily from energy that has been stored in the form of ionic concentration differences between the two sides of a membrane.
Purkinjie cells are...
Purkinje cells are in the cerebellum and represent some of the largest neurons in the brain. These cells release neurotransmitter GABA. GABA inhibits certain neurons from transmitting impulses. Purkinje cells are the sole output neurons of the cerebellar cortex and play pivotal roles in coordination, control, and learning of movements.
The sympathetic nervous system (SNS) is associated with the phrase "fight or flight". It helps the body prepare to react to stressful situations. Here are some main effects of fight or flight stimulus:
Release of sugar into the blood - increase in sugar provides energy for muscles to contract. Increase in heart rate - increase in heart rate speeds up the rate at which blood (and therefore) oxygen can be delivered to the brain and skeletal muscles. Oxygen is needed for energy. Dilation of bronchi and bronchioles - the bronchi and bronchioles are the 'tubes' that are air passages in the lungs. Dilation of these allow more air/oxygen into the lungs, which can then be delivered to the brain and skeletal muscles. Dilation of the pupil - this allows more light to enter the eye, which provides the brain with more information about the external world.
Satellite cells are....
Satellite cells - PNS same function as astrocytes have similar functions to astrocytes, but satellite cells function in the peripheral nervous system.
Schwann cells are....
Schwann cells are the cells that form insulating myelin sheath in the peripheral nervous system
Sensory (Afferent) neurons and Motor (Efferent) neurons
Sensory (or afferent) neurons enter and innervate the spinal cord via dorsal roots. Many of these signals are then integrated in the brain, which sends out an appropriate response to the stimulus. Motor (or efferent) neurons exit and send signals back to the muscles via the ventral roots. SAME DAVE
anatomy and physiology in sympathetic vs parasympathetic nervous system
So once again, it's anatomy and physiology-the structure of each of these systems is related to its function. The sympathetic nervous system is set up in such a way that even a small stress signal sent down one path could trigger a response in many effectors at once. Which is one reason why your reaction to a sudden, stressful event can feel so all-encompassing By the same token**, the resting and digesting that's overseen by the parasympathetic system doesn't require urgent, all-hands on deck communication. If you need to process a burrito or take a nap or maybe a trip to the bathroom, it can communicate with the organs involved, one on one.**
The subarachnoid space....
Subarachnoid Space: The space between the arachnoid and pia mater is called the subarachnoid space. It is here where the cerebrospinal fluid bathes and cushions the brain.
The Subdural Space....
Subdural Space: The space between the dura mater and arachnoid membranes is called the subdural space.
The Blood-Brain-Barrier......
The Blood-Brain-Barrier is a selectively semipermeable membrane that covers the brain and regulates the passage of substances from the blood into the brain. It allows the passage of certain substances into the brain and prevents/slows the passage of others. It's barrier which helps ensure the brain's cerebrospinal fluid (CSF) has a unique, specific composition compared to composition of blood.
The PNS and SNS differ in the neurotransmitters used: in the parasympathetic nervous system the neurotransmitter used....
The PNS uses acetylcholine (Ach) for both its preganglionic and postganglionic neurotransmitter. When the long preganglionic neuron synapses with the postganglionic neuron, the preganglionic neuron releases acetylcholine as the neurotransmitter to effect the postganglionic neuron. When the short postganglionic neuron synapses on its effector organ, it also releases acetylcholine as its neurotransmitter to effect the target effector organ.
The PNS and SNS differ in the neurotransmitters used: in the sympathetic nervous system the neurotransmitter used....
The SNS uses acetylcholine only as its preganglionic neurotransmitter, but uses norepinephrine (NE) and epinephrine (E) as its postganglionic neurotransmitter (aka noradrenaline and adrenaline). When the short preganglionic neuron synapses with the postganglionic neuron, the preganglionic neuron releases acetylcholine as the neurotransmitter to effect the postganglionic neuron. When the long postganglionic neuron synapses on its effector organ, it releases norepinephrine/epinephrine as its neurotransmitter to effect the target effector organ.
Relationship between stimulus and action potential
The action potential is an explosion of electrical activity that is created by a depolarizing current. This means that some event (a stimulus) causes the resting potential to move toward 0 mV.
Ca2+ Channels are used to....
The action potential that was fired and received by the dendrites activated the voltage gated Ca2+ channels in the presynaptic neuron. They exist because when these channels open up, they allow calcium to flow into the pre-synaptic neuron. This Ca2+ inflow triggers synaptic vesicles to fuse with the membrane, and via exocytosis, they release the neurotransmitters they contain into the synapse/synaptic cleft (the gap between neurons).
The autonomic nervous system can be divided into .....
The autonomic nervous system can be divided into two groups: the sympathetic nervous system and the parasympathetic nervous system.
The autonomic nervous system.....
The autonomic nervous system controls the involuntary movement of the body, such as the activity of effector organs (the organs that the nervous system can have an effect on, like the heart, lungs, pupil, GI tract, etc.) and involuntary muscles (such as cardiac muscles and smooth muscles). - autonomic nervous system innervates our internal organs -controls vital function such as heart rate, respiration and breathing, and digestion
The axolemma is the cell membrane surrounding an axon....it's two main jobs is....
The axolemma is the cell membrane surrounding an axon. 1) It is responsible for maintaining the membrane potential of the neuron 2) it contains ion channels through which ions can flow rapidly.
Soma is the .......
The cell body of the neuron is called the soma
The cell membrane is unresponsive for a short time after an action potential has occurred. This is called the _____________
The cell membrane is unresponsive for a short time after an action potential has occurred. This is called the refractory period.
The refractory period has two parts...
The cell membrane is unresponsive for a short time after an action potential has occurred. This is called the refractory period. The refractory period has two parts: 1) Absolute refractory period: Absolutely no stimulus, no matter how strong the stimulus is, it cannot elicit an action potential. This is because the Na+ channel is inactivated, so Na+ cannot flow into the cell in order to depolarize (make the cell membrane more positive) in order to pass the threshold value (-55mV) and generate a action potential (+30 mV). 2) Relative refractory period: a very strong stimulus would be needed to elicit an action potential because the cell is hyperpolarized meaning it is extremely negative so it needs a strong stimulus in order to reach its threshold potential value (-55 mV)
Our nervous system is divided into two main networks that work in harmony....
The central nervous system consisting of your amazing brain and spinal cord and the peripheral nervous system made up of the nerves coming out of that central nervous system.
How does the central nervous system and peripheral nervous system work together...?
The central nervous system's main game is integrating the sensory information that the peripheral system collects from all over the body, and responding to it by coordinating both conscious and unconscious activity. "The sun is bright, so I'll shade my eyes, I'm hungry, so I'm calling the pizza man", "the phone is ringing, maybe I'll answer it". All these sensations, thoughts, and directions process through this two part system. Its the brain of course that sorts out all the sensory information and gives orders. It also carries out your most complex functions like thinking, and feelings, and remembering. Meanwhile your spinal cord conducts two-way signals between your brain and the rest of your body while also governing basic muscle reflexes and patterns that don't need your brain's blessing to work-this is how a chicken can still run around even if the poor thing has been decapitated.
The cerebral hemispheres have distinct fissures, which divide the brain into...
The cerebral hemispheres have distinct fissures, which divide the brain into lobes. Each hemisphere has 4 lobes: frontal, temporal, parietal, and occipital. Each lobe may be divided, once again, into areas that serve very specific functions. It's important to understand that each lobe of the brain does not function alone. There are very complex relationships between the lobes of the brain and between the right and left hemispheres.
The gray matter is the outer cerebral cortex on top of the hemisphere of the brain that consists of......
The gray matter is the outer cerebral cortex on top of the hemisphere of the brain that consists of 1. Nerve cell bodies 2. Glial cells 3. Dendrites 4. Unmyelinated portions of axons Most of the brain's neuronal cell bodies are here. The gray matter includes regions of the brain involved with seeing, hearing, memory, speech, emotion, and decision making among others.
Preganglionic fibers and postganglionic fibers in the sympathetic nervous system....
The key here is that in the sympathetic nervous system, the preganglionic fibers are much shorter than the postganglionic ones. Which makes sense when you think about it, because sympathetic ganglia are really close to the spinal cord, and the axons don't need to go very far from the central nervous system. But they do have a lot of distance to cover, on the other side of the ganglion, in order to reach their effectors. So, naturally the fibers leading out of the ganglia, the postganglionic fibers, are a lot longer.
Does the membrane potential go back to its original resting state which is -70 mV?
The membrane potential doesn't just go back into its original resting state. It actually goes lower than the resting state, a state called hyperpolarization which is much more negative. This makes it more challenging for an action potential to fire, as there has to be even more excitatory stimulus to be able to raise the membrane potential threshold potential.
The mnemonic "salty banana" helps us....
The mnemonic "salty banana" helps us remember the relative ion concentrations around the cell. Imagine salt on the outside of a banana. Salt is high on the outside. Salt is NaCl, sodium chloride. Banana on the inside. Bananas are rich in K+, potassium. So we have a higher NaCl outside, and we have a higher K+ inside.
Summary of the action potential Events in Neurons
The nerve impulse is all-or-none. A stimulus opens the voltage-gated Na+ channels which cause Na= to flow into the neuron. This brings the potential to a positive value. As this occurs, we see a large change in the membrane voltage...this is action potential. Action potentials are essentially signals carrying information along the axon. We have gone from -70 mV to +30 mV for example. This is depolarization. What is a voltage-gated channel? A class of transmembrane proteins that form channels that can open and close due to a voltage. They are usually ion specific. For example, voltage-gated channels can be noted for: a) Na+ b) K+ c) Ca++ d) Cl- Now in order to generate a action potential, a certain value called the threshold must occur. Once this voltage is achieved, the neuron generates an action potential once it "fires", the size of the action potential does NOT depend on the strength of the stimulus causing depolarization. Bottom line: If you don't reach the threshold potential, nothing happens. You MUST reach the threshold voltage....thus the action potential is all-or-nothing. (Recall we started at -70 mV....a threshold for mammalian neurons is about -55 mV) Hundreds of action potential can occur each second..the greater the stimulus, the more action potentials can be generated. The cell membrane is unresponsive for a short time after an action potential has occurred. This is called the refractory period.
The nervous system can be categorized into two specific systems:
The nervous system can be categorized into two specific systems: the central nervous system and the peripheral nervous system.
The parasympathetic nervous system (PNS) is associated with the phrase _____ and controls_____
The parasympathetic nervous system (PNS) is associated with the phrase "rest and digest". It controls the body's functions when the body is resting and relaxing. It brings the body to a calm and restful state. A tip is to remember that the parasympathetic nervous system controls passive actions (both parasympathetic and passive start with the letter P).
The peripheral nervous system can be further divided into two groups....
The peripheral nervous system can be further divided into two groups: the somatic nervous system and the autonomic nervous system:
The peripheral nervous system and the central nervous work together by......
The peripheral nervous system takes inputs from the external world (sensory). Sensory inputs are relayed from the peripheral nervous system to the spinal cord, and to the relevant part of the brain. After the sensory information has been integrated, the CNS outputs command that travels back to the PNS and ultimately to effector organs.
The peripheral system has two separate divisions based on.....
The peripheral system has two separate divisions based on voluntary and involuntary responses Voluntary=somatic nervous system Involuntary = autonomic nervous system
The postsynaptic neuron is....
The postsynaptic neuron is the one that receives the neurotransmitters in the synapse by receptors.
ok...now what? We have just seen depolarization has occurred, a voltage has been generated and is moving down the axon...now what?
The presynaptic neuron has vesicles that are filled with neurotransmitters. Gated channels for Ca2+ are also present. As the action potential arrives, Ca2+ voltage-gated channels open...allowing Ca2+ to diffuse into the neuron. This ca2+ influx causes the synaptic vesicle to fuse with the presynaptic membrane. These vesicles dump their neurotransmitters into the synaptic cleft. The neurotransmitter then travels to the postsynaptic cleft right across from them and bind to the bind to the receptor located on the postsynaptic cell membrane. Each neurotransmitter has a different function. The binding will change the shape of the receptor...This allows a "passage" or entry area for ions to now cross. For example, the passage can allow Na+ and K+ ions to cross. Neurotransmitters are eventually released from the receptors and can: 1) Diffuse away 2) Be broken down by enzymes 3) Be taken up by the synaptic terminal
presynaptic neuron is........
The presynaptic neuron is the neuron that releases neurotransmitters into a given synapse.
Preganglionic fibers and postganglionic fibers in parasympathetic nervous system....
The reverse is of course true for the parasympathetic system. Since parasympathetic ganglia are so close to, or even inside of, their effector organs, the preganglionic fibers are a lot longer. They extend from the cranium and sacrum where they start, out to the lungs or liver or bladder, wherever their effector is, where they reach their ganglion. From there, the post ganglionic fibers are super short-just long enough to communicate with their effector.
The soma contains the______
The soma contain the nucleus of the neuron
The somatic nervous system controls the voluntary movement of the body, specifically the activity of______
The somatic nervous system controls the voluntary movement of the body, specifically the activity of skeletal muscles
The somatic nervous system is most related to the release of which neurotransmitter?
The somatic nervous system is the voluntary part of the nervous system that controls our skeletal muscles. The neurotransmitter that controls the contraction of our skeletal muscles is acetylcholine. Acetylcholine is the primary neurotransmitter released by lower motor neurons at the neuro-muscular junction. This produces voluntary movement, which is the goal of the somatic nervous system.
The somatic system is made up of two different types of neurons, which are also called nerve cells. The two types of neurons are....
The somatic system is made up of two different types of neurons, which are also called nerve cells. The two types of neurons are 1. sensory neurons, or afferent neurons, which transmit messages to the central nervous system 2. Motor neurons, also called efferent neurons, which relay information from the central nervous system to other areas of the body. SAME DAVE
Resting membrane potential....
The voltage or resting potential is about -70 mV There is more negative inside the cell than outside the cell. These gradients are maintained by the Na+/K+ pumps located in the plasma membrane and use ATP to actively transport Na+ out of the cell and K+ into the cell. This pump helps to maintain the resting potential (3 Na+ out; 2 K+ in). This allows for an excess of + charge outside the cell. Ion channels will allow ions to go back and forth, which could generate voltage or potential. The resting potential is also maintained by the presence of large, negatively charged molecules such as proteins which are more abundant inside the neurons. Cl- also reside more on the interior to help maintain the negative resting potential.
There are ______ pairs of cranial nerves that contain _____
There are 12 pairs of cranial nerves that are sensory, motor, and mixed
There are two (main) effects the neurotransmitters can have:
There are two (main) effects the neurotransmitters can have: excitatory and inhibitory.
Thermoreceptors....
Thermoreceptors respond to temperature-related stimuli
What would happen if a neuron was mutated such that the voltage-gated Na+ channels always remained open?
To answer this question, we need to realize that voltage-gated Na+ channels are unique channels, and are separate from the Na+/K+ ATPase. Now if voltage-gated Na+ channels always remained open, then that means sodium would be moving INTO the cell constantly and making the cell constantly positive and hence more and more depolarized (more positive) So If voltage-gated Na+ channels always remained open to let sodium into the cell (more positive coming into the cell), the sodium potassium pumps would need to work harder to maintain its negative resting membrane potential. As the Na+/K+ ATPase is powered by ATP, there would be an increased consumption of ATP. This pump is seperate from the sodium gated ion channel, this pumps job is to independently restore the negative resting membrane potential (-70mv)
IMPORTANT Na+ gated ion-channel opens up to allow Na+ inflow into cell to cause depolarization (to make more positive)... K+ gated ion-channel open up to allow K+ outflow into cell to cause repolarization (to make more negative)... The Na+ gated ion-channels and K+ gated ion-channels are separate channels from the Na+/K+ ATPase Pump. Na+/K+ ATPase Pump is only used to maintain the negative resting potential. But when it comes to getting an action potential, Na+ or K+ gated ion-channels open and close to allow Na+ in solely or K+ out solely in order to either depolarize or repolarize.
To depolarize (make more positive), Na+ gated channels are used, they open up and allow Na+ into the cell so that the cell can become more positive and hit a threshold value (-55mV), and when it does hit -55mV, more Na+ gated ion channels are encouraged to open up and it become even more positive going all the way to +30 mV which finally hits a action potential. To Repolarize (make more negative), K+ gated ion channels open up and allow K+ to exit out of the cell, making the inside of the cell more negative, this makes the cell come all the way down to hit hyperpolarization which is even below the negative -70mV resting potential.
Underneath the gray matter lies the myelinated white matter.......
Underneath the gray matter lies the myelinated white matter. The white matter consists of: 1. long nerve fibers (axons) that connect brain areas to each other This is how white matter connects various areas of the gray matter to each other and carry impulses between neurons. The white matter is the relay and communication region of the brain.
Choroid Plexus is.....
Ventricles of the brain: Ventricles (4 of them) are cavities deep in the brain interior that contain the cerebrospinal fluid. The cerebrospinal fluid is produced by specialized capillaries called the choroid plexus which consists of ependymal-like cells. The modified ependymal cells of the choroid plexus produces 500 ml of cerebrospinal fluid each day!
Step 2 to create an action potential in order to stimulate a neuron to send a signal to another neuron...
When a neuron is stimulated, it depolarizes (membrane potential becomes more positive) This occurs because the stimulus opens up gated ion channels, causing Na+ inflow into the neuron. Because positive ions flow in, the membrane potential becomes more positive.
When the neurotransmitters attach to the receptors at the post-synaptic neuron dendrites, these neurotransmitter chemical messengers can affect the neuron to act in two different ways________
When the neurotransmitters attach to the receptors at the post-synaptic neuron dendrites, these neurotransmitter chemical messengers can affect the neuron to act in two different ways: EPSP and IPSP.
Whether or not the postsynaptic neuron fires action potentials is determined by.....
Whether or not the postsynaptic neuron fires action potentials is determined by graded potential summation.
Your brain is divided into specialized regions that.....
Your brain is divided into specialized regions that may or may not interact with each other to produce a given action. We can better understand this division of labor by looking at how the brain first develops into its main component parts. Inside a developing embryo, the central nervous system starts off as a humble little neural tube, that is made from the notochord! Soon the caudal, or lower, end of the tube stretches out, forming the spinal cord, while the cranial end begins to expand, divide, and enlarge into three primary brain vesicles or interconnected chambers. This is kind of your proto-brain. We call these chambers the prosencephalon (forebrain), the mesencephalon (midbrain), and the rhombencephalon (hindbrain). By an embryo's fifth week of development, these three main chambers start morphing into 5 secondary vesicles that essentially form the roots of what will become your grown-up structures: LOOK AT CHART!!!!
1. Sites of origin of neurons from the central nervous system
Your sympathetic fibers are in the middle of your spine. Early anatomists saw how a network of nerves radiating from the middle of the spine like this could quickly coordinate the functions of many major organs at once, so it was called the sympathetic system, from the Greek words for "feeling together". But the nerve fibers of your parasympathetic system begin both above and below where the sympathetic ones do. They are craniosacral meaning they sprout from the base of your brain and just superior to your tailbone. Because the roots of these nerve fibers basically frame the starting points of the sympathetic nerves, they're called parasympathetic-literally "beside the sympathetic".
_____ is the basic functional unit of the nervous system....
neuron is the basic functional unit of the nervous system
Are the voltage-gated Na+ channels and K+ channels together or seperate from the Na+/K+ ATPase?
that voltage-gated Na+ channels and voltage gated K+ channels are unique channels, and are separate from the Na+/K+ ATPase.
the sympathetic nervous system preganglionic neurons also directly stimulate the......
the sympathetic nervous system preganglionic neurons also directly stimulate the adrenal medulla to release norepinephrine/epinephrine into the blood. These hormones help generate the fight or flight response.
