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[OS 202] A > Trans - Neuronal Excitability II > Flashcards

Trans - Neuronal Excitability II Flashcards

1
Q

transient shift of membrane potential in a localized cell area

A

local potential

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2
Q

characteristics of local potential

A
  1. localized
  2. graded
  3. decrementally transmitted
  4. may be summated
  5. very rapid
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3
Q

[T/F] local potential is faster than AP

A

T

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4
Q

types of local potential

A
  1. synaptic - IPSP or EPSP
  2. generator potential - sensory organs
  3. electronic potential - associated with AP
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5
Q

potential that occurs in sensory organs

A

generator potential

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6
Q

local potential that occurs along the axon as the action potential travels along it

A

electronic potential

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7
Q

time required for a membrane potential to change after a stimulus is applied

A

time constant

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8
Q

high resistance - ______ time constant

A

greater

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9
Q

high capacitance - _______ time constant

A

greater

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10
Q

ability to store charges of opposite signs on two opposing surfaces

A

capacitance

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11
Q

less leakage of ions across the membrane means that local potential will _________

A

travel farther from the source

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12
Q

distance at which the initial transmembrane volume change has fallen to 37% of its peak value

A

space constant

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13
Q

relationship of space constant to transmembrane resistance

A

directly related

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14
Q

relationship of space constant and internal axoplasmic resistance

A

inversely related

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15
Q

the larger the space constant, the ______ along the membrane a voltage change is observed after a stimulus is applied

A

farther

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16
Q

transmembrane resistance

A

how well a membrane blocks ions from leaving

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17
Q

the higher the transmembrane resistance, the _____ the space constant

A

higher

18
Q

internal axoplasmic resistance

A

resistance to ion flow within the axon

19
Q

how does internal axoplasmic resistance affect space constant

A

when the resistance is high, ions cannot mvove away from the source quickly –> lesser space constant

20
Q

action potential - define

A

fleeting, self-renewing wave of depolarization (positive wave) that propagates without decrement along the entire length of the nerve axon at high speed

21
Q

orthodromic conduction

A

conduction in one direction ( in axon away from soma)

22
Q

antidromic conduction

A

conduction from axon toward soma

23
Q

conformations of Na gate, and components

A
  1. resting - activation gate closed, inactivation gate open
  2. open - activation gate open, inactivation gate open
  3. inactive - activation gate open, inactivation gate closed
24
Q

effect of reaching threshold potential

A

opening of Na and K gates, action potential starts

25
Q

spike potential

A

rapid rise and fall of membrane potential due to fast sodium gates

26
Q

absolute refractory period - define

A

no new AP is produced no matter how strong the stimuli

27
Q

absolute refractory period - mechanism

A

all Na gates are already open, no new change in Na gradient can be created

28
Q

relative refractory period - define

A

stronger than normal stimulus can cause AP

29
Q

relative refractory period - mechanism

A

some Na channels are closed again - may be reopened to generate new AP

30
Q

prevents AP from reversing direction

A

relative refractory period

31
Q

supranormal refractory period - define

A

easier to reach threshold and create AP because the electrical charge inside the membrane is nearer the threshold

32
Q

supranormal refractory period - mechanism

A

continued efflux of K due to slow K channels - causes membrane potential to be relatively more negative

33
Q

subnormal period

A

overshooting of membrane repolarization due to slow K gates

34
Q

subnormal period is corrected by:

A

Na-K pump

35
Q

AP has constant ____ and _______

A

amplitude and form

36
Q

an increase in the axon diameter will (1)_______ the space constant, (2)_______ the time constant, and (3)_______ the conduction speed

A
  1. increase
  2. decrease
  3. increase
37
Q

myelinated axon conduction velocity

A

3-120 m/sec

38
Q

unmyelinated axon conduction velocity

A

0.5-2 m/sec

39
Q

presence of myelin leads to (1)_______ in effective resistance of axonal membrane. why?

A
  1. increase, because ions must flow through myelin before reaching ECF
40
Q

presence of myelin leads to (1)________ in effective capacitance. why?

A
  1. decrease, because of the greater distance between ECF and ICF
41
Q

saltatory conduction

A

electrical signal jumping from one node of ranvier to the next

[OS 202] A (18 decks)

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