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M2M Unit III > Action Potential I: Generation > Flashcards

Action Potential I: Generation Flashcards

1
Q

Threshold is the point at which _____ and ______ currents are exactly equal and opposite.

A

sodium; potassium

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1
Q

At rest, the activation gate (m) is shut and the _____ is open.

A

inactivation gate (h)

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2
Q

The K+ channel gates are _____ at rest.

A

closed

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3
Q

At rest, the _______ is shut and the inactivation gate (h) is open.

A

activation gate (m)

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3
Q

Without the _____, the membrane would repolarize very slowly.

A

voltage-gated K+ channels

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4
Q

Repolarization occurs for two reasons: 1) _____, and 2) _____.

A

P(Na) declines back to its resting level; P(K) undergoes a transient increase

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4
Q

When the membrane is depolarized, the activation gate _____ and the inactivation gate closes.

A

opens

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4
Q

The ____ channel behavior is an example of negative feedback.

A

K+

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4
Q

What is the refractory period?

A

after generating an AP, the axon cannot produce another one for a few milliseconds

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5
Q

The membrane potential must be _____ to the same level before each action potential occurs.

A

depolarized

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6
Q

When the membrane is _____, the activation gate opens and the inactivation gate closes.

A

depolarized

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7
Q

The action potential is always the same size and shape in that neuron, regardless of _______.

A

how big the stimulus is

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7
Q

What is the absolute refractory period?

A

during this time, no stimulus, no matter how strong, can evoke another AP

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9
Q

What is an action potential?

A

when the membrane undergoes a large, rapid, transient depolarization

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9
Q

The threshold is not the point at which all of the ____ open.

A

Na+ channels

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11
Q

Within each square micrometer of typical axonal membrane are about 100 ____ channels which, at rest, do not permit any ____ to cross the membrane.

A

sodium; Na+

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12
Q

The K+ channel gates open in response to ______.

A

depolarization

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13
Q

The action potential depends on the ______.

A

voltage-gated sodium channels

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13
Q

The _______ depends on the voltage-gated sodium channels.

A

action potential

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14
Q

The ‘passive’ electrical properties of axons are not sufficient to conduct an action potential ______.

A

over long distances

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15
Q

What is the relative refractory period?

A

time during which a stronger-than-normal stimulus is required to evoke another AP

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16
Q

The _____ open in response to depolarization.

A

K+ channel gates

16
Q

K+ channels close with _____.

A

a delay

17
Q

What controls the behavior of the K+ channel gate?

A

membrane potential

17
Q

Why is there a refractory period?

A

the sodium channel inactivation (h) gates require time to reopen after repolarization

18
Q

The ______ gate swings faster.

A

activation

18
Q

After _____, an axon cannot generate another one for a few milliseconds.

A

producing an action potential

19
Q

______ occurs for two reasons: 1) P(Na) declines back to its resting level and 2) P(K) undergoes a transient increase.

A

Repolarization

21
Q

Without the sodium channels, electrical signals can’t spread more than _____ from the site of the stimulus.

A

a few millimeters

22
Q

____ channels close with a delay.

A

K+

23
Q

The action potential is always the same _____ in that neuron, regardless of how big the stimulus is.

A

size and shape

24
Q

The K+ channel behavior is an example of ____ feedback.

A

negative

26
Q

At the beginning of depolarization, the membrane permeability is drastically altered from one that is largely permeable to _____ to one that is much, much more permeable to ____.

A

potassium; sodium

27
Q

The K+ channel gates ____ in response to depolarization.

A

open

29
Q

Without the _____, electrical signals can’t spread more than a few millimeters from the site of the stimulus.

A

sodium channels

30
Q

The ____ channels start conducting when the cell is depolarized a little bit.

A

Na+

32
Q

What does it mean that action potentials are all or none events?

A

the AP is always the same size and shape regardless of the stimulus

34
Q

The _____ open as the Na+ channel inactivation gates are closing.

A

K+ channels

36
Q

_______ is the point at which sodium and potassium currents are exactly equal and opposite.

A

Threshold

37
Q

The _____ is not the point at which all of the Na+ channels open.

A

threshold

39
Q

As ______ ions rush into the cell, the inside becomes more positive.

A

sodium

41
Q

What does threshold mean?

A

a certain amount of depolarization is required to initiate an AP

42
Q

As sodium ions rush into the cell, the inside becomes more _____.

A

positive

43
Q

The ____ channel gates are closed at rest.

A

K+

44
Q

When the membrane is depolarized, the activation gate opens and the ____.

A

inactivation gate closes

45
Q

After producing an action potential, an axon cannot generate another one _____.

A

for a few milliseconds

46
Q

The _______ is always the same size and shape in that neuron, regardless of how big the stimulus is.

A

action potential

47
Q

_____, the activation gate (m) is shut and the inactivation gate (h) is open.

A

At rest

49
Q

What does it mean that there is a threshold for excitation?

A

the membrane potential must be depolarized to the same level before each action potential occurs

50
Q

The Na+ opening is an example of ____ feedback.

A

positive

51
Q

Without the voltage-gated K+ channels, the membrane would _____.

A

repolarize very slowly

52
Q

The membrane potential must be depolarized to the same level before each _____ occurs.

A

action potential

53
Q

Why do K+ channels close with a delay?

A

to allow both maximum height of the AP and rapid repolarization

M2M Unit III (30 decks)

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