Class 1 - Overview/Signal Transmission Flashcards by Tempo Sabatier

Give examples of white matter found in the PNS

nerves, which are bundles of myelinated axons or dendrites

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What is a nerve?

a bundle of myelinated axons plus its associated connective tissue and blood vessels in the PNS

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Where can grey matter be found in the PNS?

ganglia

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Compare/contrast nerves vs. tracts

nerves are found in the PNS

tracts are found in the CNS and connect nuclei or areas of the cortex

both are white matter, bundles of myelinated axons

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True or false: all of the following are grey matter
Neuron cell bodies
Unmyelinated axons
Dendrites
Nuclei
Axon terminals
Neuroglia

True

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The enteric plexus is composed of ___ and ___. What layer of the digestive tract wall is each of these found?

Myenteric (Auerbach) plexus (within the muscularis)

Submucosal (Meissner’s) plexus (within the submucosa)

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What are the three types of sensory receptors?

free nerve endings (bare dendrites)
encapsulated free endings
separate cells

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What are the effectors of the somatic nervous system?

skeletal muscles

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What is the most abundant structural type of neuron?

multipolar

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The myelin sheath is formed by who in the PNS and who in the CNS?

PNS - Schwann cells

CNS - oligodendrocytes

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Most sensory neurons are of what structure?

unipolar

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Motor neurons are of what structure?

multipolar

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Most interneurons are of what structure?

multipolar

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Describe multipolar neurons

several dendrites

one axon

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Describe bipolar neurons

one main dendrite, one axon, with the cell body interrupting the path between them

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Where are bipolar neurons found?

retina of the eye, inner ear, olfactory area of the brain

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Describe unipolar neurons

dendrites and one axon that are fused together - the cell body stems off from this long process, without interrupting it

they begin in the embryo as bipolar neurons

The dendrites of most unipolar neurons function as…

sensory receptors

What is a Purkinje cell, where is it found?

a neuron with an expansive pattern of dendrite dispersion, found in the cerebellum

What is a pyramidal cell, where is it found?

a neuron found in the cerebral cortex, which as a pyramid-shaped cell body

What cells of the nervous system are capable of cell division?

neuroglial cells

Which neuroglial cells are only found in the CNS?

astrocytes
microglia
oligodendrocytes
ependymal cells

What are the functions of astrocytes?

create the BBB
regulate growth, migration, and interconnection of embryonic neurons
influence formation of neural synapses
maintain chemical environment for generation of nerve impulses

What role do oligodendrocytes play?

make and maintain myelin sheaths in the CNS

Which neuroglial cell is most numerous?

astrocytes

Describe the structure of microglia, astrocytes, oligodendrocytes, and ependymal cells

Microglia - small cells with spine-like projections Oligodendrocytes - similar to astrocytes but smaller and fewer processes Astrocytes - star-shaped with many processes Ependymal cells - have cilia and microvilli

What is the function of microglia?

phagocytosis of debris and bacteria in damaged tissue

What is the function of ependymal cells?

arranged in a single layer to line the ventricles, forming part of the blood-CSF barrier

What is the function of satellite cells?

regulate exchange of material between neuronal cell bodies and ISF

Which part of the neuron membrane is more negatively charged?

the inside surface

A cell with a membrane potential is said to be...

polarized

What is the average resting membrane potential of: neurons RBC's heart/skeletal muscle

neurons -70mV RBC's -10mV heart/skeletal muscle -90mV

Graded potentials are useful for ___ while action potentials are useful for ____

GP: short distance communication AP: long distance communication

What is 'decremental conduction'?

refers to the gradual decrease in the stimuli and resultant response along the pathway of conduction (GP decreases as it spreads)

What is 'summation'?

stacking of GP's (adding together to result in a stronger or longer stimulus) --> can be temporal summation (repeated input) or spatial summation (multiple at same time)

Graded potentials mainly occur where?

dendrites + neuron cell bodies

What is the action potential 'threshold'?

-55mV

What occurs in the depolarization phase of an action potential?

1. stimulus causes Na+ channels to open 2. Na+ ions rush into the cell 3. K+ moves out at a slower rate 4. inside of cell becomes much more positively charged, reversing the polarity

What occurs in the repolarization phase of an action potential?

1. Na+ channels close, extra K+ channels open 2. K+ moves out very quickly, resulting in the membrane potential being even more negative than originally until K+ channels close 3. Sodium-potassium pumps re-establish the required Na/K concentrations

Why does an absolute refractory period occur?

Na+ channels cannot reopen before the cell returns to its resting state

What two conditions are required in the relative refractory period to generate a second AP?

1. a larger than normal stimulus | 2. K+ channels are still open, inactivated Na+ channels have already returned to their resting state