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Physiology I > Generation of Nerve Action Potential > Flashcards

Generation of Nerve Action Potential Flashcards

1
Q

what is an action potential?

A

electrical impulse transmitted by nerve or muscle cell

change in voltage that causes cell to go from negative resting state to pos. state for brief time

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2
Q

at rest the cell membrane is highly permeable to what ion

A

K+

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3
Q

at peak of action potential the cell membrane is highly permeable to what ion

A

Na+

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4
Q

resting membrane potential is close to the equilibrium potential for

A

K+

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5
Q

when is threshold reached?

A

membrane depolarized by some electrical, mechanical, or chemical stimulus that causes influx of + charged ions

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6
Q

what happens at threshold?

A

voltage gated Na+ are opened which leads to further depolarization of the membrane (more positive)

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7
Q

describe the rising phase

A

so the threshold is reached, which means voltage gated sodium channels are opened, as the cell lets in more sodium it gets more positively charged leading to more sodium voltage gated channels to open. positive feedback, and the cell continues to get more pos. charged from all the sodium entering

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8
Q

draw a graph of the resting level, threshold, rising phase, overshoot, peak, repolarization, hyperpolarization

A

pg 8

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9
Q

what is the overshoot phase

A

membrane potential is so depolarized it reverses (that is, if resting membrane potential is around -70, at overshoot phase it will be above 0 so MUCH more + charged)

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10
Q

at the overshoot phase the membrane is most permeable to

A

Na+

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11
Q

at the overshoot phase the cell approaches equilibrium potential for

A

Na+

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12
Q

what happens at the peak phase

A

Na+ permeability starts to decrease, voltage gated K+ have been opened and the permeability of K+ increases

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13
Q

what happens at repolarization phase

A

due to the K+ being opened the membrane gets more negative

K+ ions are leaving the cell

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14
Q

what happens at afterhyperpolarization phase

A

K+ channels stay open long enough for the membrane potential to go more negative than the resting membrane potential

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15
Q

gNa means

A

conductance of sodium

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16
Q

depolarization and rising phase of action potential can be attributed to what conductance

A

gNa

increase in Na+ conductance

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17
Q

repolarization phase can be attributed to what conductance

A

gNa and gK
decrease in Na conductance
increase in K conductance

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18
Q

the return to the resting membrane potential can be contributed to what conductace

A

gK

decrease in K conductance

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19
Q

draw a graph of membrane potential, Na+ conductance and K+ conductance

A

pg 18

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20
Q

what technique was used to measure the action potential conductances

A

voltage-clamp technique

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21
Q

what does the voltage clamp technique allow

A

can hold the membrane potential constant in muscle or nerve cell and measure the ionic current flowing across the membrane

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22
Q

What does TTX stand for

A

Tetrodotoxin

23
Q

What does TEA stand for

A

tetraethylammonium

24
Q

What is function of TTX (Tetrodotoxin) and why is this helpful regarding measuring conductance

A

blocks voltage dependent Na+ conductance (permeability)

If you block the Na+ conductance you remove that variable and can see the affect of K+ without Na+

25
Q

What is the function of TEA (tetraethylammonium) and why is this helpful regarding measuring conductance?

A

blocks voltage- dependent K+ conductance (permeability).

if you block K+ conductance you remove that variable and can see the affect of Na+ without K+

26
Q

draw the Na+ current if TEA is used

A

pg 21

27
Q

draw the K+ current if TTX is used

A

pg 21

28
Q

draw the sodium voltage gate at resting, activation, and inactivation state

A

pg 22

29
Q

draw the potassium voltage gate at resting, activation, and inactivation state

A

pg 23

30
Q

elecrotonic potential vs action potential

A

pg 3

31
Q

Describe what is happening with the K+ and Na+ during resting, rising, peak, repolarization, hyperpolarization, and resting state

A

pg 24

32
Q

name four properties of action potentials

A

o Propagated without decrement
o All-or-none response
o Voltage inactivation of the action potential
o Refractory periods

33
Q

Describe the absolute refractory period

A

if another stimulus is given to the neuron during this period it will not lead to a second action potential
sodium channels cannot reopen

34
Q

what is the benefit of the absolute refractory period

A

prevents AP from traveling backward along axon

limits rate of firing of AP

35
Q

Draw on graph where the absolute and relative refactory periods are in relationship to the AP

A

pg 28

36
Q

describe the relative refractory period

A

only some of the voltage gated sodium channels are available to open, if there is a very strong stimulus the n some of the sodium voltage gated channels will open and generate another action potential

37
Q

what is accomodation

A

An increase in the threshold for an action potential that occurs in some neurons during a slowly developing or prolonged depolarization. The result is that only a few action potentials are generated during prolonged depolarization above the normal threshold level

38
Q

the more negative you are the more polar you are - that is an increase in

A

membrane potential

39
Q

hyperpolarization is an increase in

A

membrane potential

40
Q

what does ttx do

A

voltage gated sodium channels blocked by the toxin

41
Q

if pt has ttx will they get action potential

A

no

42
Q

if just voltage gated postassium channels are on will there be action potential

A

no

just hyperpolarization

43
Q

in the presence of TEA

A

prolonged action potential

b/c K+ voltage gated channels are blocked

44
Q

what does TEA do

A

blocks K+ current

45
Q

downward deflection ( when it goes downard on a current graph) what does that mean

A

downward current - Na enters cell during AP

46
Q

hyperkaleima

A

chronic elevated potassium outside cell - so say it’s at 10.

extended period of time

47
Q

what happens in hyperkalemia

A

gradietn for potassium to leave is reduced, takes longer to repolarize the membrane
voltage gated sodium channel gets stuck in activated state so you can’t recruit another AP
get depolarization and get AP and then you won’t be able to generate another AP. this is why you have muscle weakness

48
Q

succinylcholine

A

acts like or mimics hyperkalemia. potassium channel will stay open WHAT

49
Q

what does refractory mean

A

can’t do anything

50
Q

absolute refractory period ends in what phase

A

repolarization phase

51
Q

what is happening that there can be strong signal and you can get AP during relative refractory period

A

sodium channels go back to rest

52
Q

can there be AP when sodium channels are in inactivation state

A

no that is during absolute refractory period

53
Q

the farther you are from the initial AP, what happens regarding refractory period and sodium voltage gated channels

A

the farther you are from initial AP, the more sodium will be at resting (instead of in inactivation phase), and the mores sodium that are at resting the lower the threshold and the bigger the AP you can get, because then more Na channels will respond, so it’s easier to get them to respond (threshold) and they can respond greater making a bigger depolarization

Physiology I (9 decks)

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