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Physiology I > Nerve Conduction > Flashcards

Nerve Conduction Flashcards

1
Q

Draw a diagram of a myelinated nerve and action potential

A

pg 3

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2
Q

What are the two different types of nerve conduction?

A

electronic conduction

saltatory conduction

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3
Q

Where are the nodes of ranvier

A

in b/w the myelin sheathes on a nerve cell

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4
Q

electronic conduction is through a ______ neuron

A

non-myelinated

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5
Q

saltatory conduction is through a ______ neuron

A

myelinated

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6
Q

describe how action potential travels vis electronic vs saltatory conduction

A

much faster via saltatory b/c the myelin sheaths help it travel faster

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7
Q

“conduction velocity” is another way of saying

A

propagation: a AP traveling down a cell

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8
Q

what are the two passive properties of axonal membranes

A

time & space

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9
Q

time and space constants are refelctions of what

A

the physical properties of the neuronal memrane

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10
Q

describe what the time constant tells you

A

how rapidly a membrane will respond to a stimulus.

the time it takes for the membrane potential change to reach 63% of its final value.

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11
Q

RmCm represents

A

time constant

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12
Q

what variables represent time constant

A

RmCm

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13
Q

the time constant represents the amount of time it will take for the membrane potential to reach what percent of its final value

A

63%

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14
Q

the smaller the time constant, the greater

A

the propagation velocity

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15
Q

what does Rm stand for

A

Resistive properties of the membrane

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16
Q

Rm is inversely related to what

A

permeability

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17
Q

if there is high membrane resistance, there will be

A

low permeability

increased time constant

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18
Q

What does Cm stand for?

A

Membrane Capacitance

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19
Q

really generally, membrane capacitance is a fancy way for saying

A

cell size

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20
Q

the larger the membrane capacitance, the

A

the greater the amount of charge that must flow to depolarize the membrane, the longer the time constant will be.

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21
Q

What is the equation for the length (space) constant?

A

√Rmd/Ri4

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22
Q

define the length constant

A

the distance it takes for the depolarization to decay by 63%

23
Q

the greater the space constant, the

A

greater the propagation velocity

24
Q 
What does 
Rm
d
Ri
stand for in the length constant equation
A 
Rm = membrane resistance
d = diameter of axon
Ri = internal resistance
25
Q

Using the length constant, describe why humans have myelinated axons

A

In order to increase propagation velocity by a factor of 2, the axon diameter has to quadruple because of the square root relationship in the length constant formula. Not practical in humans.
√Rmd/Ri4

26
Q

another name for length constant

A

space constant

27
Q

the propagation veloctiy is directly proportional to what? inversely proportional to what?

A

directly proportional to the space constant

inversely proportional to the time constant

28
Q

what has to be done in electronic conduction in order for AP to be propegated along the entire length of the axon?

A

each adj. region has to be depolarized

29
Q

what forms myelin

A

axon wrapped in sheath of schwann cells

30
Q

what cells surround the axon in the CNS

A

Oligodendroglial cells

31
Q

what cells surround the axon in the PNS

A

schwann cells

32
Q

where is AP generated in myelnated axon

A

nodes of ranvier

33
Q

myelin does what to the membrane resistance & the membrane capitance

A

increases membrane resistane

decreases membrane capitance

34
Q

what does myelin do to Cm and Rm

A

The myelin effectively reduces the Cm and increases Rm to decrease time constant and increase length constant

35
Q

myelinated axon has greater conduction velocity than an unmyelinated axon fiber that is how much larger in diameter

A

100x

36
Q

in unmyelinated axons, what determines the conduction velocity

A

the diameter of the axon

the larger the diameter of the axon, the greater the speed of propagation

37
Q

in myelinated axons, what determmines the conduction velociy

A

the distance b/w the nodes of ranvier

the greater the distance b/w the nodes of ranvier, the greater the velocity of the AP propagation

38
Q

the larger the membrane capacitance, what happens to time constant

A

increases time it takes to make depolarization change

longer time constant

39
Q

large diameter axon compared to small diameter, resistance to flow smaller in which one

A

the large diameter axon

40
Q

a lot of resistance what happens to time constant

A

increases time constant

41
Q

low resistance to membrane (no myelin) what happens to time constant
what happens regarding capacitance

A

decrease in time constant
high capacitance

overall take more time for time constant

42
Q

the more cell membrane needed to charge up, the longer its going to take to

A

make depolarization change

43
Q

the shorter the time constant the

A

faster the velocity propagation

44
Q

if it has high resistance it likely is a

A

myelinated neuron

45
Q

why do you want resistance to be high

A

so the AP doesn’t leave

think of it as insulation

46
Q

longer length constant means what

A

it will move farther before it decays

47
Q

when you get to node of ranvier you will always trigger a

A

action potential

48
Q

capacitance goes way what with myelination

A

down

49
Q

in MS what happens

A

start loosing myelin

50
Q

what happens to conduction velocity in MS and why

A

it decreases

b/c resistance of membrane has gone down but capacitance has gone up. so the neurons will act like un-myelinated neuron

51
Q

what happens to length constant in MS

A

goes down

52
Q

what happens to time constant in MS

A

goes up

53
Q

for unmyelinated nerve conduction velocity is proprotional to

A

diameter of axon

54
Q

myelinated nerve velocity of propagation is determed by

A

distance b/w nodes of ranvier

Physiology I (9 decks)

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