A&P 1 Nervous system
Do spinal rami carry sensory or motor info?
Both.
What necessary body function is regulated by the pons (with assistance from the medulla oblongata)?
Breathing
Which functional areas are unilateral? Which hemisphere is each unilateral function area found in?
Broca's area and Wernicke's area are both unilaterally located in the left hemisphere.
From which above-listed area is cerebrospinal fluid usually obtained for analytic purposes?
Btwn L3/L4 or L4/L5
There is one pair of spinal nerves which do not have a dermatome, which pair is it?
C1 nerves.
Cervical spinal cord
C1-C7
CEREBROSPINAL FLUID SYSTEM OF THE BRAIN AND SPINAL CORD
CEREBROSPINAL FLUID SYSTEM OF THE BRAIN AND SPINAL CORD
1. Identify the main functions of the nervous system.
COLLECT INFO. (Ex. Receptors in the skin detect stimuli associated with touch and relay it along nerves to the spinal cord and brain) PROCESS AND EVALUATE INFO. The brain and spinal cord determine what response, if any, is required. INITIATE RESPONSE TO INFO. The brain and spinal cord initiate a response as motor output via nerves to effectors (all three muscle tissue types and glands). The result is muscle contraction or change in gland secretion.
What is in the central canal?
CSF
What is the path of a drop of CSF from its source to its entrance back into the blood stream?
CSF is produced by the choroid plexus in the ventricles (in lateral and 4th ventricles). CSF flows from the lateral ventricles, through the interventricular foramen to the third ventricle, and then through the cerebral aquaduct into the 4th ventricle CSF in the fourth ventricle flows into the subarachnoid space by passing through the paired lateral apertures or the single median aperture, and into the central canal of the spinal cord As the CSF flows through the subarachnoid space, it removes waste products and additional fluid from the brain, and provides buoyancy to support the brain Excess CSF flows into the arachnoid villi, then drains into the dural venous sinuses. The greater pressure on the CSF in the subarachnoid space ensures that CSF moves into the venous sinuses without permitting venous blood to enter the subarachnoid space
What fluid bathes the cauda equina?
CSF.
Function of funiculi
Carry info up to or away from brain
Gray matter (spinal cord)
Centrally located; shape resembles a letter H or a butterfly. Darker because a contains a lot less myelin.
Identify which spinal cord nerve group (cervical, thoracic, lumbar, sacral or coccygeal) will receive SENSORY info from which area of the skin.
Cervical: head and neck (but not face - CN V the trigeminal nerve innervates the face), back of arms and front of arms except middle of anterior arm (T1 and T2 innervate this), hands dorsal and palmar. Thoracic: Chest, stomach, underarm and middle of anterior arm Lumbar: hips, upper and lower legs except posterior of legs, tops and bottoms of feet Sacral: genitalia, most of butt, middle of posterior legs and sides of distal legs and lateral sides of feet.
16. Understand the difference between a chemical gradient and an electrical gradient and provide an example of each as it relates to a neuron.
Chemical gradient: more of a chemical on one side of the membrane than the other. Ex. There is more K+ inside the neuron than out, and more Na+ outside the neuron than in. Electrical gradient: more of a positive or negative charge on one side of the membrane than the other. At RMP, there is a negative charge inside the neuron and a more positive charge outside the neuron.
Ependymal cells
Ciliated CNS neuroglia that play an active role in moving the cerebrospinal fluid; line ventricles; contribute to BBB.
Spinal cord dura mater is continuous with what structure at the inferior terminus of the vertebral canal?
Coccygeal ligament. (Filum terminale)
Conus medullaris
Cone shaped inferior tapering of spinal cord, ending at approximately L1.
Brain stem
Connection to spinal cord. Filters information flow between peripheral nervous system and the rest of the brain.
33. What is the difference between continuous and saltatory conduction? Why is saltatory conduction faster than continuous conduction?
Continuous conduction (2 meters/second) occurs in unmyelinated axons and involves the sequential opening of voltage-gated Na+ channels located within the axon plasma membrane (axolemma). Saltatory conduction (120 meters/second) occurs in myelinated axons. Here, action potentials do not occur in regions that are myelinated - rather they are propagated only at neurofibril nodes (nodes of Ranvier). Myelinated regions of an axon contain limited numbers of voltage-gated Na+ channels and K+ channels, and myelin is a great insulator that prevents ion movement even if additional channels are present. -An action potential occurs at neurofibril nodes/nodes of Ranvier. Depolarization occurs and Na+ diffuses into the axon. (This is followed by repolarization ans v-gated K+ channels open and K+ diffuses out.) -In myelinated regions, the Na+ diffuses through the axoplasm of the axon under the axolemma (which is insulated by myelin). Two critical aspects to note: It is relatively fast, faster than events at the nodes of Ranvier and as Na+ diffuses through the axoplasm it experiences resistance and the local current becomes weaker with distance. -Then that relatively weak An+ current is still sufficient to cause the opening of the c-gated Na+ channels at the next node of Ranvier, producing a new action potential. This process repeats until it reaches the synaptic knobs. It's called saltatory conduction because the action potential occurs only at neurofibril nodes/nodes of Ranvier; thus it seems to "jump" from node to node. Saltatory conduction is faster and more efficient (less E required by Na+/K+ pumps to maintain RMP).
Cranial vs spinal nerves
Cranial nerves (12 pairs) extend from the brain and spinal nerves (31 pairs) extend from the spinal cord.
DERMATOMES
DERMATOMES
Longitudinal fissure
Deep groove running from the front to the back of the brain, separating the two different hemispheres
Subarachnoid space
Deep to arachnoid mater; filled with cerebrospinal fluid which provides buoyancy and protection
Where is the subarachnoid space?
Deep to the arachnoid mater and filled with CSF.
Diencephalon
Deep/internal part of the brain that contains thalamus and hypothalamus
Pia mater
Deepest layer; very thin, shrink wrapped around spinal cord; supports some of the blood vessels supplying the spinal cord.
The pathways (tracts) that carry motor info are called:
Descending tracts
Cerebral peduncles
"little foot"; motor tracts located on the anterolateral surfaces of the midbrain. Descending axon bundles project through the cerebral peduncles and carry voluntary motor commands from the primary motor cortex of each cerebral hemisphere.
Cauda equina
"tail of horse"; nerve roots (groups of axons) project inferiorly from the spinal cord.
29. Know the difference between an excitatory post synaptic potential (EPSP) and Inhibitory post synaptic potential (IPSP)
(Two types of graded potentials aka postsynaptic potentials) EPSP (Excitatory Post Synaptic Potential) 1. Excitatory neurotransmitter crosses synaptic cleft and binds to receptor that is a chemically gated cation channel, causing it to open. 2. More Na+ moves doen its concentration gradient into the neuron than K+ moves out. 3. The inside becomes slightly more positive/less negative because of the influx of positively charged ions. This temporary less negative state is called an EPSP. 4. The local current of Na+ becomes weaker as it moves along the neuron plasma membrane toward the axon hillock and decreases in intensity with the distance traveled. IPSP (Inhibitory Post Synaptic Potential) 1. Inhibitory neurotransmitter crosses synaptic cleft and binds to either a chemically gated K+ channel or a chemically gated Cl- channel, depending upon the neurotransmitter and channels present. 2. If neurotransmitter binds to receptor that is K+ channel, it opens and K+ moves out of the neuron down its concentration gradient, causing loss of + ions. If neurotransmitter binds to Cl- chemically gated channel, Cl- flows down it concentration gradient into the neuron, causing a gain in - charge. The amount of neurotransmitter determines the number of channels that open. 3. The inside of the cell becomes slightly more negative either way. This temporary, more negative, state is called an IPSP. 4. The local current of ions becomes weaker as it moves along the neuron plasma membrane toward the axon hillock and decreases in intensity with the distance traveled.
Cerebral nuclei
(basal nuclei, basal ganglia) Clusters of gray matter that contain neuron cell bodies and lie within masses of white matter *Involved in the control of motor functions
Cerebral functional areas...
... see below
Diencephalon...
... see below
Midbrain...
... see below
Brain stem...
... see below Connects the brain and spinal cord
Central white matter of cerebrum
.... see below
Internal anatomical areas of the cerebrum: give approx. internal locations and general functions
.... see below
7. What are the functional classes of neurons? Identify the three basic types, their function, and location.
1. Sensory (afferent) neurons conduct signals from receptors in the PNS to CNS. (Ex. skin) Their purpose is to detect stimuli and pass it on to the CNS. Usually unipolar neurons. 2. Interneurons (association neurons) are confined to the CNS. They integrate and process stimuli and choose appropriate responses. They are multipolar neurons. 3. Motor (efferent) neurons conduct signals from the CNS to PNS and effectors such as muscles and glands. Cell body is usually in CNS and these neurons are mulitpolar as well.
Why are the 12 pairs of nerves that exit the brain (the cranial nerves) considered part of the PNS?
12 cranial nerve paris are the peripheral nerves exiting from the various regions of the lower brain and skull. Although they are located within the skull, cranial nerves are considered part of the peripheral nervous system because they convey messages to and from the body's muscles and glands.
Rami communicantes
2 branches off anterior ramus
19. Ions tend to want to move to dispel electric potentials. A major way neurons maintain or reestablish a resting membrane potential is to use the Na/K pump. Describe and know the steps of the Na/K pump in detail. a. Is the Na/K pump an active or passive process? b. Does the Na/K pump require energy? If so, where does it come from? c. Do Na and K move against or along chemical and/or electrical gradients?
3 sodium ions and ATP bind to sites on the cytoplasmic surface of the sodium-potassium pump. ATP is split into ADP and a phosphate group, resulting in both the binding of the P to the pump, and the release of energy that causes the sodium-potassium pump to change conformation (shape) and release the Na+ into the ECF. Two K+ ions from the interstitial fluid (part of the ECF directly around the cell) then bind to sites on the outer cellular surface of the sodium-K+ pump. At the same time, the P produced earlier by ATP hydrolysis is released into the cytosol. The transport protein reverts back to its original shape, resulting in the release of the K+ ions into the cytosol. The Na+/K+ pump is now ready to being the process again. It is active, requires energy in the form of ATP, and Na and K move against their concentration gradients.
How many pair of CERVICAL nerves are there? How many cervical vertebrae are there?
8 pairs of nerves but only 7 vertebra.
Pons...
A brain structure that relays information from the cerebellum to the rest of the brain
What is a nerve?
A cablelike bundle of parallel axons that are components of the PNS. A single axon typically must be viewed with a microscope, but a nerve can be seen without.
Cerebrospinal fluid
A clear, colorless body fluid found in the brain and spine. It is produced in the choroid plexuses of the ventricles of the brain.
Limbic system
A doughnut-shaped system of neural structures at the border of the brainstem and cerebral hemispheres; associated with emotions such as fear and aggression and drives such as those for food and sex. Includes the hippocampus, amygdala, and hypothalamus.
Arachnoid mater
A fine, delicate membrane, situated between the dura mater and the pia mater and deep to the subdural space. It is fibrous (webby).
Consider the posterior root ganglion. What is a ganglion? Why is it bigger in diameter than the rest of the posterior root? What special cells are in the ganglia?
A ganglion is a structure containing a number of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fiber.
What is a subdural hematoma?
A hemorrhage that occurs int he subdural space between the dura mater and arachnoid mater. Result from ruptured veins caused by fast/violent rotational motion of the head. Blood pools in space and compresses the brain.
Choroid plexus
A highly vascular portion of the lining of the ventricles that secretes cerebrospinal fluid.
Cerebellum...
A large structure of the hindbrain that controls fine motor skills.
Cerebral aquaduct/Aquaduct of Sylvius
A narrow canal passes through the midbrain and connects the third ventricle with the sickle-shaped fourth ventricle.
Hypothalamus
A neural structure lying below (and sort of anterior to) the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.
Frontal lobe
A region of the cerebral cortex that has specialized areas for movement, abstract thinking, planning, memory, and judgement
Occipital lobe
A region of the cerebral cortex that processes visual information
Parietal lobe
A region of the cerebral cortex whose functions include processing information about touch.
22. Describe and graph the action potential series of events during the opening and closing of voltage gated channels. Use the terms threshold, depolarization, repolarization, hyperpolarization, and resting membrane potential.
A resting potential is -70 mV. A stimulus opens chemically gated Na+ channels to open in the receptive area of the neuron. Na+ ions start to flood in, and they flow along the inside of the membrane, parallel to it. If the stimulus is large enough, Na+ ions will flood in to the point that the voltage along the dendrites and soma will make a more positive charge inside the cell. If the voltage reaches its threshold (-55 mV), then that will be enough to stimulate the Na+ voltage gated channels in the axon hillock, where an action potential will then be propagated throughout the entire axon as Na+ channels open consecutively along its length. K+ chemical (in the receptive segment) and K+ voltage gated channels also open shortly after the Na+ chemical and voltage gated channels open, and they repolarize the cell by flowing out of the cell, creating a more negative charge. Because K+ channels are open longer than Na+ channels, hyperpolarization may occur, leading to a mV of less than -70. Na+ and K+ pumps return the cell to its RMP of -70 mV, and now the whole thing can happen again.
30. Does the opening of one post synaptic channel opening cause an action potential? Explain.
A single EPSP is incapable of causing the postsynaptic neuron to reach threshold and so it cannot create an action potential by itself. Graded postsynaptic potentials are added together in the initial segment in a process called summation. So a single channel opening would not cause an action potential.
Mid brain (part of brain stem)
A small structure between the hindbrain and forebrain that relays information from the eyes, ears, and skin and that controls certain types of automatic behaviors
What is a dermatome?
A specific segment of skin supplied by a single spinal nerve. All spinal nerves except for C1 innervate a segment of skin, and so each of these nerves is associated with a dermatome.
Central canal
A tiny channel found within the spinal cord and inferior medulla oblongata
ANATOMY
ANATOMY
AREAS OF CEREBRUM
AREAS OF CEREBRUM
AREAS OF THE SPINAL CORD
AREAS OF THE SPINAL CORD
34. Identify the four main types of neurotransmitters.
Acetylcholine - excites skeletal muscle, inhibits cardiac muscle, can do both to smooth muscle and glands Amino acids - learning and memory... Monoamines - sleep, memory, mood, behavior... Neuropeptides - pain info, feelings of well being...
26. Explain an action potential, where it typically occurs in the neuron, what gated channels are involved, what minimum voltage is required, its intensity over time/distance, and if it can cause depolarization and/or hyperpolarization?
An action potential happens in the initial segment (axon hillock) and is propagated along the axon. A change in voltage from RMP (-70 mV) to -55 mV opens Na+ voltage gated channels , allowing Na+ to flow in and creating a more positive charge (depolarization) down along the axon, opening more Na+ channels, and having more Na+ flowing in. Once the voltage reaches +35 mV, K+ voltage gated channels open, and K+ flows out of the cell, leading to a more negative charge back again inside the cell (repolarization). K+ voltage gated channels stay open longer than Na+ voltage gated channels and so a hyperpolarization can occur, where the voltage is below the RMP (-70 mV). Na+ and K+ then restore the membrane back to RMP.
When anesthetic is injected for epidural anesthesia, where does the anesthetic go to cause numbness? How does it cause numbness? What part of the body is numbed?
An epidural goes into the epidural space (the space superficial to the dura mater. It numbs the nerves of whichever nerves are associated with that particular vertebra.
Motor info leaving the spinal cord to reach spinal nerves will be found in which horns?
Anterior gray horns
Which of the 2 nerve roots contains sensory info only?
Anterior root
Consider the peripheral nerves that innervate the arms and legs. Do they originate from the posterior rami or the anterior rami?
Anterior.
Cervical enlargement
Around approx. C4-C7/T1 because more tissue in/out of this are for arms (pectoral appendages).
The pathways (tracts) that carry sensory info are called:
Ascending tracts
5. Describe axonal transport, where it occurs, how it occurs and its general purpose. Know the difference between retrograde and anterograde transport.
Axons depend on cell body to provide them with newly synthesized materials, and to break down or recycle their used materials. To accomplish this, substances are moved in both directions through an axon. Anterograde is from cell body to synaptic knobs. Retrograde is from knobs to body. Fast axonal transport (400 mL/day) -via microtubules -antero or retro -substances in cell body moved toward knobs (antero) -Used vesicles to be broken down and recycled and potentially harmful agents are moved from knob to body (retro). Slow Axonal transport (.1-3 mm/day) -results from flow of axoplasm (axoplasmic flow is another name) -antero only -substances are enzymes, cytoskeletal components, new axoplasm for axon regeneration
BE ABLE TO DRAW A TYPICAL NEURON WITH ALL ABOVE STRUCTURES
BE ABLE TO DRAW A TYPICAL NEURON WITH ALL ABOVE STRUCTURES
Why are the spinal enlargements enlarged?
Because more nerves exit/enter for appendages.
Will motor info be traveling up the spinal cord or down it?
Down.
Which two menignes are essentially bound together to form one?
Dura mater and arachnoid mater.
Which of the meninges is outermost? Middle? Innermost?
Dura mater, arachnoid mater, pia mater.
Which is toughest and most durable?
Dura mater.
The epineurium is continuous with what wrapping of the spinal cord?
Dura mater. (M)
************Spinal cord dura mater is continuous with what structure wrapping the brain?
Dura mater?????????
17. Describe the ECF and ICF environment during a resting membrane potential of -70mV in a neuron. How is that RMP maintained?
During a RMP of -70 mV, there is more Na+ and a positive charge in the ECF. There is more K+ and a negative charge in the ICF. The RMP is maintained via Na+/K+ pumps and leak channels within the plasma membrane. There are more K+ leak channels and K+ moves through more easily than does Na+ through its leak channels.
Interventricular foramina
Each lateral ventricle communicates with the third ventrical through this opening. It connects the lateral ventricles to the third ventricle.
Posterior root ganglion
Enlarged because it holds collections of cell bodies of neurons. (sensory nerves enter)
Spinal cord dura mater is continuous with what structure wrapping the spinal nerves?
Epineurium.
8. Where do you find the endoneurium, perineurium and epineurium? What are they composed of and what's their function?
Epineurium: (Dense irregular connective tissue - DICT) Encloses entire nerve (bundle of axons wrapped in connective tissue), and provides protection and support. Perineurium: (DICT) wraps around fascicles (bundles of axons); supports blood vessels. Endoneurium: (loose areolar CT) electrically insulates and separates axons; surrounds myelin of myelinated axons; within are capillaries that supply each axon.
What are effectors? Which division of the PNS will relay info from the CNS to effectors?
Examples of effectors are skeletal muscle (somatic) or cardiac and smooth muscle as well as glands (autonomic). The MOTOR nervous system will relay info from the CNS to these effectors.
What is the function of the arachnoid villi?
Excess CSF moves across the arachnoid villi to return to the blood within the dural venous sinuses.
3. What are the properties or characteristics unique to neurons? Which of these properties are shared with muscle tissue? Which is/are only unique to nerve tissue?
Excitability - responsiveness to stimulation Conductivity - electrical changes quickly propagated along plasma membrane following stimulation Secretion - neurons release neurotransmitters in response to conductive activity Extreme longevity - most neurons formed during fetal development are still functional in old age Amitotic - during fetal development of neurons, mitotic activity is lost in most neurons, except those in the olfactory epithelium of the nose and in certain areas of the brain. Excitability and conductivity are properties shared with muscle tissue, but secretion, extreme longevity and being amitotic is unique to nerve tissue.
Falx cerebelli
Extends into the midsagittal line inferior to the tentorium cerebelli; a sickle-shaped vertical partitiion that divides the left and right cerebellar hemispheres.
White matter (spinal cord)
External to the gray matter. White because contains myelinated axons.
Arachnoid villi/Arachnoid granulations
Fingerlike extensions of the arachnoid mater project through the dura mater (the meningeal layer of the dura mater) into the dural venous sinuses to form arachnoid villi. Excess CSF moves across the arachnoid villi to return to the blood within the dural venous sinuses.
Neurolemmocyte (PNS)
Flattened cell wrapped around a portion of an axon in the PNS Myelinates and insulates PNS axons; allows for faster action potential conduction along an axon in the PNS
Satellite cell (PNS)
Flattened cell; groups of these cells cluster around neuronal cell bodies in a ganglion Protects and regulates nutrient and waste exchange for cell bodies in ganglia
Cerebrospinal fluid
Fluid in the space between the meninges that acts as a shock absorber that protects the central nervous system.
Lateral gray horn
Found in the thoracic area (T1-L1) only. They contain the cell bodies of autonomic motor neurons, which innervate cardiac + smooth muscle and glands.
9. What are the types of glial cells? What are the functions and where are they found?
Glial cells are found in the CNS and PNS and hold nervous tissue together. They don't transmit signals, but they protect, support, and nourish neurons. They vastly outnumber neurons and are much smaller than neurons. They are also capable of mitosis.
Posterior ramus/dorsal ramus
Goes posteriorly
27. Compare/contrast local potentials and action potentials
Graded potential vs. Action potential Neuron segment: Dendrites and cell body vs Axon Channels: chemically gated vs voltage gated Direction of voltage change: Pos. or neg. vs positive and then negative Amount of volt. change: relatively small vs relatively large (causing temporary change in polarity) Degree of volt. change: depends on magnitude of stimulus vs. generally does not vary Duration: 1 msec to a few msec vs travels length of axon Change in intensity: decreases with distance vs same intensity because voltage gated channels continue to open in sequence.
Are cell bodies and synapses more likely to be in white or gray matter?
Gray matter
Will short interneurons that communicate across (anterior/posterior not up down) the spinal cord be in white matter or gray matter?
Gray matter.
Median aperture
H
Posterior root (dorsal root)
Has enlarged bulb called posterior root ganglion (sensory nerves enter)
Temporal lobe
Hearing
Intervertebral foramen
Hole formed between 2 vertebrae where the nerves exit.
Tentorum cerebelli
Horizontally oriented fold of dura mater that separates both the occipital and temporal lobes of the cerebrum from the cerebellum.
INTERNAL ANATOMY OF THE SPINAL CORD
INTERNAL ANATOMY OF THE SPINAL CORD
Insula
In each hemisphere of the mammalian brain the insular cortex (often called insula, insulary cortex or insular lobe) is a portion of the cerebral cortex folded deep within the lateral sulcus (the fissure separating the temporal lobe from the parietal and frontal lobes). Memory and taste.
Motor association area/premotor cortex
In frontal lobe
Primary somatosensory area
In postcentral gyrus Receives sensory info
Primary motor area
In precentral gyrus
Decussation of the pyramids
In the caudal region of the medulla, most of these axons cross to the opposite side of the brain at a point called decussation (to cross over in the form of an X) of the pyramids. As a result of the crossover, each cerebral hemisphere controls the voluntary movement of the opposite side of the body.
Pia mater
Inner layer of meninges; intimately attached to brain following contours; carries small blood vessels to nourish underlying nervous tissue;
Through which bony aperture in the vertebrae to spinal nerves leave the protection of the spinal column?
Intervertebral foramina.
Define the term autonomic.
Involuntary or unconscious; relating to the autonomic nervous system.
What is a nerve plexus?
It is a netowrk of interweaving anterior rami of spinal nerves. The anterior rami of most spinal nerves form nerve plexuses on both the right and left sides of the body. They then split into multiple "named" nerves that innervate various body structures. Each anterior ramus extends to body structures through several different branches. In this way, damage to a single segment of the spinal cord or to a single spinal nerve generally does not result in complete loss of innervation to a particular muscle or region of skin. (pl. plexuses)
What is a nerve fiber?
It is synonymous with the axon of a neuron. A nerve is formed of a bundle of many such fibers.
Medulla oblongata
It is the most caudal (inferior) portion of the brainstem and is continuous with the spinal cord inferiorly. The caudal portion of the medulla has a flattened, rounded shape and narrow central canal. As the central canal extends rostrally toward the pons, it enlarges and becomes the 4th ventricle. All communication between the brain and spinal cord involves tracts that ascend or descend through the medulla oblongata.
Wernicke's area
L hemisphere; multiassociation area; integrates all areas; language comprehension
At what vertebra does the actual true spinal cord end?
L1/L2
Sacral plexus
L4-S4: Innervates legs/distal legs, the sciatic nerve is one such named nerve in this plexus.
What is gray matter gray?
Lack of/less myelinated axons
Astrocyte (CNS)
Large cell with numerous processes; in contact with neurons and capillaries; most common type of glial cell Help form the blood-brain barrier with their perivascular feet (controls movement of substances from exiting the blood and entering the nervous tissue in the brain; protects the delicate neurons of the brain from toxins but allows needed nutrients to pass); regulates tissue fluid composition; replicates to occupy space of dying neurons; assists with neuronal development; provides structural support and organization to the CNS
Denticulate ligaments
Lateral extensions of pia mater that help anchor spinal cord and link to dura mater. Denticulate = teeth. The shape is triangular, so sort of like shark teeth. :)
15. Review the difference between leakage channels, chemical gated channels and voltage gated channels. In which part of the neuron are you more likely to find chemical gated channels? Voltage gated channels?
Leakage channels: always open Chemical gated channels: open due to chemical changes -Found in receptive area of neuron (dendrites) Voltage gated channels: open due to changes in voltage -Found in initial, conductive, and transmissive areas of neuron
Epidural space
Lies between dura mater and the inner walls of the vertebra, and houses areolar connective tissue, blood vessels, and adipose connective tissue.
Subarachnoid space
Light blue area in image with CSF
Projection tracts
Link the cerebral cortex to both the inferior brain regions and the spinal cord.
Fourth ventricle
Located between the pons and the cerebellum; sickle shaped; opens to subarachnoid space via a single median aperture and paired lateral apertures; narrows at its inferior end before it merges with the slender central canal in the spinal cord.
MENINGES OF THE BRAIN
MENINGES OF THE BRAIN
MENINGES (membranes) OF THE SPINAL CORD
MENINGES OF THE SPINAL CORD
************What attaches the spinal cord to the skull at the foramen magnum?
Medulla oblongata????
What is the singular form of the word meninges?
Meninx
Are microglia really nervous tissue or are they actually another type of tissue? Explain.
Microglia nuclei are typically oval-shaped, and projecting out from their cell bodies are slender elongated processes that enable the cells to move via chemotaxis (movement along a chemical gradient). These cells mediate immune responses in the central nervous system by acting as macrophages, clearing cellular debris and dead neurons from nervous tissue through the process of phagocytosis (cell eating). The embryonic origin of microglia is distinct from other types of neuroglia. Whereas other neuroglia are derived from an embryonic layer of tissue known as neuroectoderm, which gives rise to nervous tissue, microglia are derived from embryonic mesoderm, which gives rise to cells of the blood and immune system. In developmentally mature organisms microglia also can be generated from white blood cells known as monocytes that circulate in the blood and move into the central nervous system. Microglia are activated by inflammation in the central nervous system, which may be triggered by neurological degenerative disorders
Dura mater
Most superficial; really rough; deep to epidural space; provides stability to the spinal cord; fuses to the epineurium of nerves.
Anterior root (ventral root)
Motor axons leaving spinal cord
6a. Multipolar neurons
Multiple nerve processes extend directly from the cell body; typically many dendrites and one axon. This is the most common type. They are located in the central nervous system (brain and spinal cord) and in autonomic ganglia. All motor neurons are multipolar. And some are interneurons.
18. What would happen if only non-gated, continuously open (leakage) ion channels existed. How would the ions listed in #17 above want to move if left on their own?
Na+ and K+ would equalize on both sides of the membrane, leading to a complete lack of membrane potential for signal conduction. There would be a neutral charge on either side of the membrane, as well.
Cervical nerves and cervical plexus
Nerves C1-C8 are the 8 pairs of cervical nerves. C1 nerve is located just above the atlas (C1 vertebra), and C8 nerve is just above T1 vertebra. [Remember there are only 7 cervical vertebra] Of these 8 pairs, the cervical plexus consists of nerves C1-C4.
Brachial plexus
Nerves C5-T1: innervates the arms
Lumbar plexus
Nerves L1-L4: innervate the hips/thighs/legs
11. What is the difference between Schwann cell or Neurolemmocyte and neurilemma?
Neurilemma is a part of a neurolemmocyte/Schwann cell. It is the part of the cell that contains the cytoplasm and nucleus of the Schwann cell. A neurolemmocyte wraps around an axon and begins to form consecutive layers. The inner layers form the myelin sheath, and the outer layer is the neurilemma.
28. Can we perceive or feel graded potentials?
No, we will only feel them if they reach threshold at the axon hillock and initiate an action potential.
Is the cauda equina actually part of the true spinal cord? What is it?
No. It is a collection of nerve roots.
13. Describe an unmyelinated neuron in the PNS?
Not all axons are myelinated. Unmyelinated axons in the PNS are also associated with neurolemmocytes, however no myelin sheath covers them. The axon merely rests in a depressed portion of the neurolemmocyte, but its plasma membrane does not form repeated layers around the axon. In the CNS, unmyelinated axons are not associated with oligodendroctyes.
CNIII
Oculomotor; movement of eyes; MOTOR/efferent
CNI
Olfactory; smelling; SENSORY/afferent; cribriform plate in ethmoid bone; bipolar nerves
White commissure
On either side of the gray commissure
Where are the mammillary bodies? Why are they named as such?
One of a pair of small round bodies, located on the undersurface of the human brain, that act as a relay for impulses coming from the amygdalae and hippocampi to the thalamus, and (as part of the diencephalon) form part of the limbic system. Mammillary means "resembling a breast or nipple"
6d. Anaxonic neurons
Only dendrites and no axons. Different from others because produce local electrical changes called graded potentials, but do not produce action potentials. They are found in the brain and retina.
Broca's speech area/motor speech area
Only in L hemisphere; frontal lobe Breathing and speech
CNII
Optic nerve; services eyes, optic foramen; SENSORY/afferent
Anterior ramus/ventral ramus
Outside the CNS + largest branch
PHYSIOLOGY
PHYSIOLOGY
Medulla oblongata
Part of the brainstem that controls vital life-sustaining functions such as heartbeat, breathing, blood pressure, and digestion.
Epithalamus *Pineal gland
Partially forms the posterior roof of the diencephalon and covers the third ventricle. The posterior portion houses the pineal gland and habenular nuclei Pineal gland - endocrine gland that secretes hormone melatonin (circadian rhythm)
Which two meninges re-join the filium terminale in order to form the coccygeal ligament? To what does this ligament attach?
Pia and dura mater; the ligament attaches to the coccyx.
The filum terminale is an extension of which of the meninges?
Pia mater
Which of meninges is very thin and delicate?
Pia mater
What is an epidural hematoma?
Pool of blood forming in the epidural space due to severe blow to head. Adjacent brain tissue becomes distorted and compressed as result. Death may occur if bleeding not stopped.
Spinal nerve (mixed nerve)
Posterior and anterior root (mixed because contains both sensory and motor nerves).
Sensory information entering the spinal cord from spinal nerves will be found in which horn?
Posterior gray horn.
Which of the 2 nerve roots contains sensory information only?
Posterior root
Precentral gyrus
Primary motor control area; part of frontal lobe E
Postcentral gyrus
Primary somatosensory area; part of pareital lobe D
Auditory association area
Process auditory info; temporal lobe
Primary auditory area
Receive auditory info; temporal lobe B
Primary gustatory area
Receives impulses for taste; in insula
Primary visual area
Receives visual info 12; occipital lobe
What are receptors? Which division of the PNS will relay info from receptors to the CNS?
Receptors are like the eyes, skin, ears (somatic) or blood vessels and internal organs (visceral). The SENSORY nervous system will relay info from these receptors to the CNS.
Somatosensory association area
Recognition, interpretation, make sense of info from post central gyrus; parietal lobe
Define the term somatic.
Relating to or involving skeletal (voluntary) muscle and the innervation of the latter, as distinct from the viscera or visceral (involuntary) muscle and its (autonomic) innervation. Conscious and purposeful reactions to stimuli.
What is the difference between the spinal roots and the spinal rami?
Roots are in the CNS, rami are in the PNS.
Oligodendrocyte (CNS)
Rounded, bulbous cell with slender cytoplasmic extensions; extensions wrap around CNS axons Myelinates and insulates CNS axons; allows faster action potential conduction along axons in the CNS.
SPINAL CORD NERVES (name locate and identify)
SPINAL CORD NERVES (name locate and identify)
SPINAL NERVE STRUCTURES AS THEY LEAVE THE SPINAL CORD
SPINAL NERVE STRUCTURES AS THEY LEAVE THE SPINAL CORD
2. Understand the organization of the nervous system. It may be helpful to make an organizational chart showing the anatomical and functional divisions and their subdivisions.
STRUCTURAL ORGANIZATION: CENTRAL NERVOUS SYSTEM (brain and spinal cord) PERIPHERAL NERVOUS SYSTEMS (nerves and ganglia [clusters of neuron cell bodies located along nerves]) FUNCTIONAL ORGANIZATION: SENSORY NERVOUS SYSTEM - detects stimuli and transmits info from receptors to the CNS SOMATIC SENSORY - sensory input that is consciously perceived from receptors (eyes, skin, ears) VISCERAL SENSORY - not consciously perceived from blood vessels and internal organs (heart) MOTOR NERVOUS SYSTEM - initiates and transmits info from the CNS to effectors SOMATIC MOTOR - motor output that is consciously controlled; effector is skeletal muscle AUTONOMIC MOTOR - motor output that is not consciously or voluntarily controlled; effectors are cardiac muscle, smooth muscle, and glands
6. Identify and/or diagram the different neurons based on processes extending from the soma. (This is also described as classifying neurons based on shape or structure.)
See below.
Central sulcus
Separates frontal lobe from parietal lobe
Lateral sulcus
Separates temporal lobe from parietal and frontal lobes
Ependymal cell (CNS)
Simple cuboidal or columnar epithelial cells that line cavities in brain and spinal cord; cilia on apical surface Lines ventricles of brain and central canal of spinal cord; assists in production and circulation of CSF.
6c. Unipolar neurons
Single short cell process extends directly from the cell and looks like a T as a result of the fusion of two processes into one long axon. Combined peripheral process (from dendrites to cell body) and central process (from cell body into CNS) Unipolar (pseudo-unipolar) neurons are SENSORY neurons with cell bodies in spinal and cranial nerve ganglia.
Microglial cell (CNS)
Small cell with slender branches from cell body; least common type of glial cell Defends against infectious agents and engulfs debris from dead or dying neurons
What space contains the CSF?
Subarachnoid space
Where is the epidural space?
Superficial to the dura mater and deep to the walls of the vertebrae.
Thoracic spinal cord
T1-T12
Thoracic nerves
T1-T12. T1 nerve is just below T1 vertebra, and T12 is just below T12 vertebra (and above L1).
Lumbar spinal cord
T12-L2
Lumbar enlargement
T7 or 8 to T12/L1 because of more tissue in pelvic appendages (legs)
23. Explain the "all or none" law regarding action potentials and why they are irreversible and nondecremental.
The all or none law applies to action potentials proagated along plasma membranes of neurons. If the threshold is reached, an action potential is propagated along the axon without decreasing in intensity (ALL). If only a subthreshold value is reached, it is not propagated (NONE). Additionally values greater than the threshold result in the same intensity of response as the threshold.
Pyramids of the medulla
The anterior surface of the medulla oblongata exhibits two longitudinal ridges called the pyramids, which house the motor projection tracts called the corticospinal (pyramidal) tracts.
What areas of the body do the anterior rami innervate?
The anterior/ventral and lateral (arms/legs).
12. What is a Node of Ranvier? What is an Internode?
The axons in many nerves in the body have hundreds or thousands of neurolemmocytes along their entire length. The gaps between them are neurofibril nodes, or nodes of Ranvier. An internode is actually a stretch of a nerve cell axon sheathed in myelin, between two nodes of Ranvier.
Central canal
The central canal, also known as ependymal canal, is the cerebrospinal fluid-filled space that runs longitudinally through the length of the entire spinal cord. The central canal is continuous with the ventricular system of the brain.
What sulcus separates the precentral and postcentral gyrus?
The central sulcus.
Cerebellum
The cerebellum receives information from the sensory systems, the spinal cord, and other parts of the brain and then regulates motor movements. The cerebellum coordinates voluntary movements such as posture, balance, coordination, and speech, resulting in smooth and balanced muscular activity.
There is one dermatome which is not served by spinal nerves. Instead a pair of cranial nerves receive this sensory info to relay to the CNS. Which one is it?
The dermatome of the face slightly above the chin and up to the forehead, and between the ears is innervated by the Trigeminal nerve (CN V).
Pituitary gland
The endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.
************What is the relationship between ependymal cells and the blood-brain barrier?
The ependymal cells lining the choroid plexus of the ventricles help actively in the formation of cerebrospinal fluid by providing higher concentration of sodium and chloride ions and lower concentration of other substances in CSF than that of plasma.Ependymal cells make up the blood-CSF barrier.
What space separates the dura mater of the spinal cord from the periosteum of the vertebrae?
The epidural space.
Dura mater
The external, tough, dense irregular connective tissue layer composed of two fibrous layers (within the cranium). The meningeal layer is immediately superficial to the arachnoid mater. The periosteal layer (the more superficial layer) forms the periosteum on the internal surface of the cranial bones. The meningeal layer is usually fused to the periosteal layer, except in specific areas where these two layers separate to form large, blood filled spaces called dural venous sinuses (sinus is modified vein).
What attaches the spinal cord to the coccyx?
The filum terminale.
Through which bony aperture of the skull does the spinal cord ascend into the brain?
The foramen magnum.
Sympathetic chain ganglia
The ganglia of the sympathetic nervous system. They deliver information to the body about stress and impending danger, and are responsible for the familiar fight-or-flight response. They contain approximately 20,000-30,000 nerve cell bodies and are located close to and on either side of the spinal cord in long chains.
Gray commissure
The horizontal bar of the "H" that surrounds the central canal. The left and right communicate via the gray commissure.
Arbor vitae
The inner area of white matter in the Cerebellum that is organized into narrow branches that resemble those of a tree.
10. What is myelin?
The insulating covering around the axon that consists of repeating concentric layers of plasma membrane of glial cells. 80% fat, 20% protein
Through which bony apertures of each vertebra do the spinal nerves exit the spinal cord?
The intervertebral foramina.
Anterior (vental) median fissure
The inward crease on the anterior portion of the spinal cord (which coincides with the anterior portion of the vertebra).
Posterior (dorsal) median sulcus
The inward crease/gap on the posterior of the spinal cord, directly across from the anterior median fissure.
Falx cerebri
The largest of the four dural septa (membranous partitions that separate specific parts of the brain and provide additional stailization and support to the brain). Other three are the tentorium cerbelli, falx cerebelli, and diaphragma sellae.
Anterior gray horn
The left and right anterior masses of gray matter. The anterior horns pirmarily house the cell bodies of somatic motor neurons, which innervate skeletal muscle.
Posterior gray horn
The left and right posterior masses of gray matter. The axons of sensory neurons and the cell bodies of interneurons are located in these horns. *Note that the cell bodies of these sensory neurons are not found in the posterior horns; rather, they are located int he posterior root ganglia.
Right and left hemispheres
The left side of the brain is responsible for controlling the right side of the body. It also performs tasks that have to do with logic, such as in science and mathematics. On the other hand, the right hemisphere coordinates the left side of the body, and performs tasks that have do with creativity and the arts. Both hemispheres are connected by the corpus callosum and serve the body in different ways.
Lumbar nerves
The lumbar part of the spinal CORD starts above L1 vertebra and ends just above L1. Extensions of the lumbar part (nerves L1-L5) travel down from there. L1 nerve comes out just below L1 and L5 nerve comes out just below L5 - but the CORD stops above L1. The portion of the spinal cord that extends below is called the cauda equina. (horse tail).
Why is the BBB more permeable in the hypothalamus and pituitary gland?
The median eminence of the hypothalamus connects the hypothalamus to the pituitary gland. The pituitary gland releases the hormones oxytocin, which controls milk release, and vasopressin, which regulates water balance. The pituitary gland is not covered by the blood-brain barrier because the hormones it secretes need to go into circulation and pass through the rest of the body.
Filum terminale
The middle root; within the cauda equina; a thin strand of pia mater that helps anchor the conus medullaris to the coccyx.
21. What is threshold depolarization? How is it achieved? What is the significance of threshold depolarization in terms of an action potential?
The minimum voltage change to open voltage-gated channels in called the threshold value. Depolarization occurs when the charge along the inside of the membrane becomes more positive, due to the influx of Na+ ions through their Na+ voltage-gated channels. A nerve impulse arrives at synaptic end bulbs of one neuron, allowing Ca2+ gates to open, causing the vesicles to migrate toward the synapse, release their neurotransmitters, and then open the Na+ chemically gated channels in the dendrites of the next neuron, (and K+ opens after to repolarize the cell) and the influx of Na+ changes the voltage inside the cell to -55 mV (the threshold value). It reaches the axon hillock, then stimulates the voltage gated Na+ channels to open. The action potential then propagates along the entire axon, opening Na+ and K+ voltage gated channels as it goes, depolarizing and repolarizing the inside of the membrane of the neuron. When it gets to the
Large nerves have thier own blood, lymph, and nerve (VANL) supply. Through which of the connective tissue layers listed above does the VANL travel through?
The perineurium.
Pons (part of brain stem)
The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.
What areas of the body do the posterior rami innervate?
The posterior.
What makes white matter white in color?
The presence of myelinated axons
Generally where is the reticular formation located? What is the function of the reticular formation?
The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. The reticular formation is not anatomically well defined because it includes neurons located in diverse parts of the brain. The neurons of the reticular formation all play a crucial role in maintaining behavioral arousal and consciousness.
The medulla oblongata is continuous with what structure inferiorly? What marks the margin between these two structures?
The spinal cord, with which it merges at the opening (foramen magnum) at the base of the skull.
In what space is the CSF found?
The subarachnoid space. To extract CSF, needle inserted into subarachnoid space.
************What structure of the CSF circulation system travels through the midbrain?
The third ventricle?
Through which bony aperture of each vertebra does the spinal cord travel along its length?
The vertebral foramen.
Sacral nerves
There are five sacral nerves, S1-S5. The sacral part of the spinal cord coincides with the area of L1 vertebra. The nerves swing down from there, to come out just below S1 fused vertebra. S5 nerve comes out just below S5 vertebra.
Septum pellucidum
There are two lateral ventricles in the cerebgrum, separated by a thin medial partition called the septum pellucidum.
6e. Interneurons
These lie entirely within the CNS. They receive stimulation from many other neurons and carry out the integrative function of the nervous system - that is they receive, process, and store info and decide how the body responds to the stimuli. They facilitate communication between sensory and motor neurons. It is estimated that 99% of our neurons are interneurons; most are multipolar.
What are the rami communicantes? How do they differ from the anterior and posterior rami?
These rami contain axons associated with the autonomic nervous system. Each set of rami communicantes extends between the spinal nerve and a ball like structure called the sympathetic trunk ganglion. They are interconnected and form a beaded necklacelike structure called the sympathetic trunk.
Coccygeal nerves
This is the most inferior tip of the spinal cord. Only 1 pair of coccygeal spinal nerves arise from this part. Co1 appears to come all the way from the sacral part of the spinal cord, and extends down into the coccyx. It gives sensory innervation of the skin in the coccygeal region.
CNV
Trigeminal (maxilla, mandible, forehead); MIXED!!
CNIV
Trochlear nerve; MOTOR/efferent; involved in balance
6b. Bipolar neurons
Two nerve cell processes extend directly from the cell body; one dendrite and one axon. Bipolar neurons are relatively rare. They are SENSORY neurons found in olfactory epithelium, and the retina of the eye.
14. Describe a functional disadvantage of unmyelinated nerve? What is an anatomical advantage?
Unmyelinated nerves can't conduct action potentials as quickly and aren't insulated. However they are "cheaper" to make because they don't cost as much in resources. It costs a significant amount in metabolic energy to produce the many layers of lipid-rich membrane that comprise myelin. They also help decrease the bulk and weight of the nervous system.
Will sensory info be traveling up the spinal cord or down?
Up - going to brain!
CNX
Vagus; vagrant/wanders all over body; lungs, heart, gastro, pelvic; MIXED
Lateral ventricles of brain
Ventricles are cavities of expansions within the brain that are derived from the neural canal. All are lined with ependymal cells and contain CSF. There are 4 in the brain. There are two lateral ventricles in the cerebrum, separated by a thin medial partition called the septum pellucidum.
25. Explain a graded potential, describe how it is local, where it typically occurs in the neuron, what gated channels are involved, its intensity over time/distance, and if it can cause depolarization and/or hyperpolarization?
Voltage changes occur either as a graded/local potential or as an action potential. Graded/local potentials occur in the receptive segment of a neuron (dendrites and cell body) in response to stimuli, they can create a positive (depolarization) or a negative (hyperpolarization) voltage change but either way it is relatively small. They involve CHEMICALLY gated channels and last a very short time, and the distance traveled by ions and thus the change in polarity is very small. The intensity of the change decreases with distance due to the ions meeting with resistance experienced because of moving against the contents of the cytosol.
Arachnoid mater
Weblike middle layer of the three meninges
24. What is a refractory period and when does it occur?
When depolarization and repolarization are happening, this is a period called the absolute refractory period, and the neuron cannot respond to a new stimulus. A relative refractory period is during hyperpolarization. The neuron can be stimulated, but it takes a stronger stimulus to reach the threshold voltage, because the starting voltage is a lot more negative.
Are axons more likely to be in white matter or gray matter?
White matter.
Will sensory and motor info in the tracts be traveling in gray or white matter?
White matter.
Third ventricle
Within the diencephalon is a smaller, thinner ventricle called the third ventricle; between the two lobes of the thalamus gland; CSF is made here too and drains into the 4th vent. via the cerebral aquaduct.
Subarachnoid space
a space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid
4. Diagram the basic structure of a neuron include or show the following a) Cell body/soma b) Nucleus nucleolus c) Mitochondria d) Nissl bodies (What are these?) e) Neurofibrils (What are these?) f) Lipofuscin g) Dendrites h) Axons i) Axon hillock j) Trigger zone k) Axon collaterals l) Axolemma m) Axoplasm n) Synaptic end bulb or synaptic knobs o) Synaptic vesicles p) Synapse q) Schwann cell or Neurolemmocyte or Internode r) Node of Ranvier or Neurofibril node
a) Cell body/soma - the portion of the neuron that dendrites and axons extend from; this is enclosed by a plasma membrane and contains cytoplasm and a nucleus; it serves as the neuron's control center; conducts electrical signals to the axon which is initiated within the cell body or received by dendrites. b) Nucleus nucleolus - nucleus contains genetic info, nucleolus is a small dense spherical structure in the nucleus of a cell during interphase. c) Mitochondria - processes of respiration and energy production occur here; double membrane; inner layer folded inward to form cristae. d) Nissl bodies/chromatophilic substance - Free and bound ribosomes go by this name because they stain darkly with basic dyes and were first described by Franz Nissl. Gray matter is colored so because of chromatophilic substance and the absense of myelin. Nissl bodies are producers of neurotransmitters. e) Neurofibrils - Part of the cytoskeleton; nuerofilaments aggregate to form bundles called neurofibrils and extend as a complex network through the neuron, where their tensile strength provides support. f) Lipfuscin - a yellow to brown, granular, iron-negative lipid pigment found particularly in muscle, heart, liver, and nerve cells; it is the product of cellular wear and tear, accumulating in lysosomes with age. g) Dendrites - tend to be relatively short, small processes that branch of the cell body; some have 1, others have many; dendrites conduct electrical signals toward the cell body (receivers); more dendrites = more input. h) Axons - aka nerve fiber; typically longer process from cell body to make contact with other neurons, muscle cells or gland cells. i) Axon hillock- First part of axon is triangular region called axon hillock. j) Trigger zone - rich in voltage-gated Na-channels; located near or in the axon hillock; once the trigger zone is 'triggered' to threshold (from -70mV to -55mv), then an action potential occurs... The initial segment is sometimes called the trigger zone because what occurs there is similar to what happens with a gun. Sufficient pressure is applied to the trigger of a gun and the bullet is fired from the chamber, or insufficient pressure is placed on the trigger and the gun is not fired. Likewise, the bullet travels at the same velocity regardless of whether the pressure placed on the trigger is greater than needed. k) Axon collaterals - Axons give rise to a few side branches called axon collaterals; most axons and their collaterals branch extensively at their distal ends into fine terminal extensions (axon terminals) l) Axolemma - Plasma membrane of an axon m) Axoplasm - cytoplasm of axon n) Synaptic end bulb or synaptic knobs - The extreme tips of axon terminals; slightly expanded regions o) Synaptic vesicles - found in synaptic end bulbs and contain neurotransmitter p) Synapse - A synaptic knob meets another neuron or a myofiber at a functional junction called a synapse. q) Schwann cell or Neurolemmocyte or Internode - flattened cells that ensheath PNS axons to form a myelin sheath which allows for faster action potential propagation within the PNS. r) Node of Ranvier or Neurofibril node - gaps between neurolemmocytes
20. When considering the propagation of nerve impulses there are three "potentials" to think about. a. What is a potential? b. What is a resting membrane potential? c. What is a local/graded potential? d. What is an action potential?
a. A potential, such as a membrane potential is a difference in charge across a cell membrane. It can be altered to create electrical currents, and the electrical currents can be propagated down an axon. b. RMP is the voltage (charge) difference across the cell membrane when the cell is at rest. RMP is a product of the distribution of charged particles (ions). Graded potential vs. Action potential Neuron segment: Dendrites and cell body vs Axon Channels: chemically gated vs voltage gated Direction of voltage change: Pos. or neg. vs positive and then negative Amount of volt. change: relatively small vs relatively large (causing temporary change in polarity) Degree of volt. change: depends on magnitude of stimulus vs. generally does not vary Duration: 1 msec to a few msec vs travels length of axon Change in intensity: decreases with distance vs same intensity because voltage gated channels continue to open in sequence.
Association tracts
connect different regions of the cerebral cortex within the same hemisphere. Pinkish red lines in image
Corpus callosum
large; c-shaped commissural tract (extensions between the cerebral hemispheres through axonal bridges called commissures)
Subdural space
located between the dura mater and the arachnoid membrane in the skull and vertebral column (imaginary/potential)
Superior sagittal sinus
one of the six venous channels in the posterior of the dura mater that drains blood from the brain into the internal jugular vein
Thalamus
paired oval masses of gray matter that lie on either side of the third ventricle. interthalamic adhesion is small midline mass of gray matter connecting right and left thalamic bodies... like a little button.
Visual association area
process visual info; occipital lobe
In what bony depression does the pituitary gland lie?
sella turcica
Transverse fissure
separates the cerebrum from the cerebellum
Medulla oblongata (part of brain stem)
the medulla oblongata is a major structure located in the lower half of the brainstem. It is responsible for the regulation of your heart rate, breathing, and blood pressure as well as reflexes such as vomiting, sneezing, and coughing.
Cerebral cortex
the outer layer of the cerebrum (the cerebral cortex ), composed of folded gray matter and playing an important role in consciousness.
Cerebrum
the principal and most anterior part of the brain in vertebrates, located in the front area of the skull and consisting of two hemispheres, left and right, separated by a fissure. It is responsible for the integration of complex sensory and neural functions and the initiation and coordination of voluntary activity in the body.