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Anatomy & Physiology Exam 3
Histology of Nervous Tissue
50
Anatomy
Undergraduate 2
04/12/2010

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Term
what are neuroglia/glial cells?
what do i need to remember for the test about these cells!?
Definition
-support cells (5 types)
1) astrocytes
2) microglia
3) ependymal cells
4) oligodendrocytes
5) schwann cells
*THEY DO NOT PRODUCE ACTION POTENTIALS*
Term
what are astrocytes?
functions?
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
Term
how do neuroglia help maintain RMP in neurons?
how do they facilitate gas/nutrient exchange?
which type?
Definition
-by soaking up excess extracellular potassium
-by anchoring neurons to blood vessels
-astrocytes
Term
what is the most abundant type of neuroglia?
Definition
-astrocytes
Term
what are microglia?
-functions?
Definition
-PROTECT central nervous system by differentiating into microphages that participate in phagocytosis
Term
how do neuroglia protect the central nervous system? what type does this?
Definition
-by differentiating into microphages that participate in phagocytosis
-microglia
Term
what are ependymal cells?
-functions?
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
Term
what purpose does cilia have in ependymal cells?
Definition
-helps in cerebral spinal fluid circulation
Term
what are oligodendrocytes?
Definition
-produce a lipid-like myelin sheath around axons in central nervous system
Term
what are schwann cells?
Definition
-produce myelin sheath around axons in peripheral nervous system
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?
Definition
-central=oligodendrocytes
-peripheral=schwann cells
-purpose of myelin: helps in conduction of action potentials
Term
what are neurons/nerve cells?
-what do they lose?
-what do they need?
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
Term
what kind of metabolic rate do neurons have?
Definition
-ver high, so need a constant supply of oxygen and glucose
Term
what are the 3 types of neurons? (structurally)
Definition
1) multipolar neurons (most interneurons & ALL motor/efferent neurons)
2) bipolar neurons (sensory/afferent)
3) unipolar (or pseudounipolar) neurons (sensory/afferent)
Term
what do multipolar neurons have?
Definition
-3 or more processes
-most common type
-ALL multipolar neurons are somatic efferent neurons (carry action potential to skeletal muscle neurons only)
Term
what is most common type of neuron?
Definition
-multipolar neuron
Term
what do bipolar neurons have?
Definition
-1 axon & 1 dendrite extending from cell body, though dendrite may branch
-rare and specialized
-serve as receptors in the retina & olfactory mucosa
Term
what serves as receptors in olfactory mucosa and retina?
Definition
-bipolar neurons
Term
what are unipolar (pseudounipolar neurons)?
Definition
-have 1 process coming from the cell body that divides into 2 branches: peripheral process (PP) & central process (CP)
Term
what is the peripheral process? (PP)?
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
Term
what is the central process? (CP)?
Definition
-one of 2 branches that come from a single process off the cell body of a unipolar neuron
-enters the central nervous system
Term
how are neurons functionally classified?
3 types?
Definition
-based on the direction that the nerve impulse travels relative to the central nervous system
1) sensory/afferent
2) interneurons
3) motor/efferent
Term
how are sensory/afferent neurons structurally classified?
-what do they do?
Definition
-mostly bipolar & unipolar neurons
-transmit action potentials from sensory receptors in skin or viscera to the central nervous system
Term
how are interneurons classified structurally?
-what do they do?
Definition
-mostly multipolar neurons
-lie entirely within central nervous system
-shuttle signals through central nervous system pathways where integration takes place
Term
how are ALL motor/efferent neurons structurally classified?
Definition
-ALL multipolar neurons
-transmit impulses (signals, messages ap) from central nervous system to effector organs (muscles or glands)
Term
what factors influence the rate of action potential conduction?
Definition
1) axon diameter
2) degree of myelination
Term
how does axon diameter influence the rate of action potential conduction?
Definition
-the LARGER the axon diameter, the FASTER the conduction
-a larger diameter has less resistance to electrical flow
Term
how does the degree of myelination influence the rate of action potential conduction?
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
Term
what does continous conduction mean? saltatory conduction?
Definition
-continuous = slower (unmyelinated axons)
-saltatory = faster (myelinated axons)
Term
what is the soma?
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
Term
what are somas called in the peripheral nervous system? central nervous system?
Definition
-ganglia (ganglion) = peripheral
-nuclei = central
Term
what are dendrites?
Definition
"input zone"
-receives signals & sends them toward the soma
-part of soma, but have own special function
Term
what part of the soma sends signals toward the soma?
Definition
-dendrites
Term
what is the axon hillock?
Definition
"trigger zone"
-sums incoming signals (inhibitory & excitatory)
-generates an action potential IF summation = threshold
Term
when does the axon hillock generate action potential?
Definition
-if the summation equals threshold
Term
what is the axon?
Definition
"conducting zone"
-conducts, or propagates, the action potential
-propagate = to reproduce & to spread
Term
what part of a neuron propagates the action potential?
Definition
-axon (means reproduce and to spread)
Term
what are the axonal/terminal branches?
Definition
-carries signals or action potential to several extensions
-the action potential is the same strength in all branches
Term
what are axonal terminals?
Definition
"secretory zone"
-release neurotransmitters or neurohormones to communicate with another neuron, muscle, or gland
Term
what do neurotransmitters/neurohormones communicate with?
Definition
-neuron, muscle, or gland
-happens through axonal terminals "secretory zone"
Term
what is myelin?
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
Term
what are nodes of ranvier? how does action potential travel through them?
Definition
-gaps b/w myelin which create "bare axonal spaces"
-action potential "jumps" from node to node via saltatory conduction
Term
what are the classes of neurons based on diameter, degree of myelination, and speed of action potential conduction?
Definition
1) group A fibers
2) group B fibers
3) group C fibers
Term
how are group A,B,C fibers classified?
Definition
-based on:
1) diameter
2) degree of myelination
3) speed of action potential conduction
Term
group A fibers:
-speed?
-type of motor neuron?
-innervate where?
-size?
Definition
-fastest
-somatic fibers
-innervate skin, skeletal muscle, & joints
-largest in diameter
-heavily myelinated
Term
what type of neuron has largest diameter and are most heavily myelinated?
Definition
-group A fibers
Term
which class of neurons are the fastest in speed of action potential conduction?
Definition
-group A fibers
Term
group B fibers:
-speed?
-size?
-myelinated?
-type of motor neuron?
Definition
-moderate speed of action potential conduction
-autonomic (visceral)
-intermediate in diameter
-lightly myelinated
Term
which type of neuron are autonomic (visceral) with light myelination?
Definition
-group B fibers
Term
group c fibers:
-speed?
-type of motor neuron?
-myelination?
-size?
Definition
-slowest speed of action potential conduction
-autonomic (visceral) fibers
-unmyelinated
-small diameter
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