Term
what are neuroglia/glial cells?
what do i need to remember for the test about these cells!? |
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Definition
-support cells (5 types)
1) astrocytes
2) microglia
3) ependymal cells
4) oligodendrocytes
5) schwann cells
*THEY DO NOT PRODUCE ACTION POTENTIALS* |
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Term
what are astrocytes?
functions? |
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Definition
-most abundant of neuroglia
-ANCHOR neurons in blood vessels, facilitating gas & nutrient exchange
-SOAK up excess extracellular potassium (help maintain rmp in neurons
-RECYCLE released neurotransmitters |
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Term
how do neuroglia help maintain RMP in neurons?
how do they facilitate gas/nutrient exchange?
which type? |
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Definition
-by soaking up excess extracellular potassium
-by anchoring neurons to blood vessels
-astrocytes |
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Term
| what is the most abundant type of neuroglia? |
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Definition
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Term
what are microglia?
-functions? |
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Definition
| -PROTECT central nervous system by differentiating into microphages that participate in phagocytosis |
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Term
| how do neuroglia protect the central nervous system? what type does this? |
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Definition
-by differentiating into microphages that participate in phagocytosis
-microglia |
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Term
what are ependymal cells?
-functions? |
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Definition
-type of neuroglia that line cavities in the brain & spinal cord that contain cerebral spinal fluid (CSF)
-most ependymal cells have cilia to help in cerebral spinal fluid circulation |
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Term
| what purpose does cilia have in ependymal cells? |
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Definition
| -helps in cerebral spinal fluid circulation |
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Term
| what are oligodendrocytes? |
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Definition
| -produce a lipid-like myelin sheath around axons in central nervous system |
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Term
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Definition
| -produce myelin sheath around axons in peripheral nervous system |
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Term
which neuroglial cells produce a myelin sheath around axons in central nervous system? peripheral?
what is the purpose of the myelin sheath, or myelin? |
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Definition
-central=oligodendrocytes
-peripheral=schwann cells
-purpose of myelin: helps in conduction of action potentials |
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Term
what are neurons/nerve cells?
-what do they lose?
-what do they need? |
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Definition
-specialized to conduct action potentials throughout body
-lose ability to divide and reproduce at maturity, so have extreme longevity
-have high metabolic rate, so need constant supply of oxygen & glucose to prevent irreversible damage |
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Term
| what kind of metabolic rate do neurons have? |
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Definition
| -ver high, so need a constant supply of oxygen and glucose |
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Term
| what are the 3 types of neurons? (structurally) |
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Definition
1) multipolar neurons (most interneurons & ALL motor/efferent neurons)
2) bipolar neurons (sensory/afferent)
3) unipolar (or pseudounipolar) neurons (sensory/afferent) |
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Term
| what do multipolar neurons have? |
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Definition
-3 or more processes
-most common type
-ALL multipolar neurons are somatic efferent neurons (carry action potential to skeletal muscle neurons only) |
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Term
| what is most common type of neuron? |
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Definition
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Term
| what do bipolar neurons have? |
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Definition
-1 axon & 1 dendrite extending from cell body, though dendrite may branch
-rare and specialized
-serve as receptors in the retina & olfactory mucosa |
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Term
| what serves as receptors in olfactory mucosa and retina? |
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Definition
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Term
| what are unipolar (pseudounipolar neurons)? |
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Definition
| -have 1 process coming from the cell body that divides into 2 branches: peripheral process (PP) & central process (CP) |
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Term
| what is the peripheral process? (PP)? |
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Definition
-1 of 2 branches of the single process that comes from the cell body in a unipolar neuron
-associated with sensory nerve endings (receptors) in periphery |
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Term
| what is the central process? (CP)? |
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Definition
-one of 2 branches that come from a single process off the cell body of a unipolar neuron
-enters the central nervous system |
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Term
how are neurons functionally classified?
3 types? |
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Definition
-based on the direction that the nerve impulse travels relative to the central nervous system
1) sensory/afferent
2) interneurons
3) motor/efferent |
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Term
how are sensory/afferent neurons structurally classified?
-what do they do? |
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Definition
-mostly bipolar & unipolar neurons
-transmit action potentials from sensory receptors in skin or viscera to the central nervous system |
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Term
how are interneurons classified structurally?
-what do they do? |
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Definition
-mostly multipolar neurons
-lie entirely within central nervous system
-shuttle signals through central nervous system pathways where integration takes place |
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Term
| how are ALL motor/efferent neurons structurally classified? |
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Definition
-ALL multipolar neurons
-transmit impulses (signals, messages ap) from central nervous system to effector organs (muscles or glands) |
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Term
| what factors influence the rate of action potential conduction? |
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Definition
1) axon diameter
2) degree of myelination |
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Term
| how does axon diameter influence the rate of action potential conduction? |
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Definition
-the LARGER the axon diameter, the FASTER the conduction
-a larger diameter has less resistance to electrical flow |
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Term
| how does the degree of myelination influence the rate of action potential conduction? |
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Definition
-myelinated axons exhibit saltatory (faster) conduction, which means myelinated areas are "skipped."
-unmyelinated axons exhibit continuous (slower) conduction, which means no axonal areas are skipped |
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Term
| what does continous conduction mean? saltatory conduction? |
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Definition
-continuous = slower (unmyelinated axons)
-saltatory = faster (myelinated axons) |
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Term
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Definition
cell body
-contains nucleus & all other organelles
-grouped by function in the central n.s. = nuclei
-grouped by function in peripheral n.s. = ganglia |
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Term
| what are somas called in the peripheral nervous system? central nervous system? |
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Definition
-ganglia (ganglion) = peripheral
-nuclei = central |
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Term
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Definition
"input zone"
-receives signals & sends them toward the soma
-part of soma, but have own special function |
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Term
| what part of the soma sends signals toward the soma? |
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Definition
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Term
| what is the axon hillock? |
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Definition
"trigger zone"
-sums incoming signals (inhibitory & excitatory)
-generates an action potential IF summation = threshold |
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Term
| when does the axon hillock generate action potential? |
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Definition
| -if the summation equals threshold |
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Term
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Definition
"conducting zone"
-conducts, or propagates, the action potential
-propagate = to reproduce & to spread |
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Term
| what part of a neuron propagates the action potential? |
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Definition
| -axon (means reproduce and to spread) |
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Term
| what are the axonal/terminal branches? |
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Definition
-carries signals or action potential to several extensions
-the action potential is the same strength in all branches |
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Term
| what are axonal terminals? |
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Definition
"secretory zone"
-release neurotransmitters or neurohormones to communicate with another neuron, muscle, or gland |
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Term
| what do neurotransmitters/neurohormones communicate with? |
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Definition
-neuron, muscle, or gland
-happens through axonal terminals "secretory zone" |
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Term
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Definition
-fatty protein coating axon in discrete areas
-functions to speed the conduction of action potential
-gaps b/w myelin are called nodes of ranvier, which create bare, axonal spaces |
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Term
| what are nodes of ranvier? how does action potential travel through them? |
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Definition
-gaps b/w myelin which create "bare axonal spaces"
-action potential "jumps" from node to node via saltatory conduction |
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Term
| what are the classes of neurons based on diameter, degree of myelination, and speed of action potential conduction? |
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Definition
1) group A fibers
2) group B fibers
3) group C fibers |
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Term
| how are group A,B,C fibers classified? |
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Definition
-based on:
1) diameter
2) degree of myelination
3) speed of action potential conduction |
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Term
group A fibers:
-speed?
-type of motor neuron?
-innervate where?
-size? |
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Definition
-fastest
-somatic fibers
-innervate skin, skeletal muscle, & joints
-largest in diameter
-heavily myelinated |
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Term
| what type of neuron has largest diameter and are most heavily myelinated? |
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Definition
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Term
| which class of neurons are the fastest in speed of action potential conduction? |
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Definition
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Term
group B fibers:
-speed?
-size?
-myelinated?
-type of motor neuron? |
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Definition
-moderate speed of action potential conduction
-autonomic (visceral)
-intermediate in diameter
-lightly myelinated |
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Term
| which type of neuron are autonomic (visceral) with light myelination? |
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Definition
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Term
group c fibers:
-speed?
-type of motor neuron?
-myelination?
-size? |
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Definition
-slowest speed of action potential conduction
-autonomic (visceral) fibers
-unmyelinated
-small diameter |
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