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NEU211 Intro to Neuro > Action Potential > Flashcards

Action Potential Flashcards

Exam 1

1
Q

What do we use to measure Action Potential?

A

Microelectrode inside the axon

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2
Q

Graded potentials

A

SHORT distances; does not reach threshold

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3
Q

Action potentials

A

LONG distances; reach the threshold

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4
Q

Depolarization

A

Membrane potential becomes more (+); Away from RMP

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5
Q

Repolarization

A

Membrane potential becomes more (-); Towards RMP

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6
Q

Hyperpolarization

A

Membrane potential becomes even more (-) than normal resting potential because

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7
Q

What causes action potentials? (2)

A
  1. Incoming signals from another neuron
  2. Sensory signals from environment
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8
Q

What is the value of threshold?

A

-55mV

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9
Q

What is the value of RMP?

A

-70mV

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10
Q

What is the value of peak AP?

A

+30mv

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11
Q

What is happening during resting state of AP?

A

All gated Na+ and K+ channels are closed; only leak channels are open

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12
Q

Voltage-Gated channels

A

Open at a certain voltage specific to the subtype

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13
Q

What maintains RMP? (2)

A

The Na+/K+ ATPase pump and leak channels

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14
Q

What is happening at threshold of AP?

A

The membrane has been depolarized by 15-20mV; Na+ permeability increases

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15
Q

For an axon to fire, _________________________

A

depolarization must reach threshold

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16
Q

If a depolarization event does not produce an AP, it produces a

A

graded potential

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17
Q

Conformational change

A

Membrane repels positive amino acids in the NA+ Voltage channels

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18
Q

Voltage sensor

A

Part of the channel that is sensitive to membrane voltage changes

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19
Q

What is happening at the depolarization phase of AP?

A

At threshold, all Na+ channels open; voltage reaches +30 mV; SIGNAL IS PROPOGATED

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20
Q

Why does the peak value top off at +30mV?

A
  1. Kinetics (timing) of the VG Na+ channels
  2. At +30mv, VG K+ channels open
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21
Q

How do the Na+ channels temporarily close?

A

The ball and chain that plugs the Na+ pore

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22
Q

Does K+ flow in or out of the membrane?

A

Out

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23
Q

What happens at the repolarization phase of AP?

A

VG K+ channels open up; positive K leaves the cell, making it more negative; Internal negativity is restored

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24
Q

What happens during hyperpolarization in AP

A

K+ keeps leaving because of a slow gate, so the cell becomes extra negative

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25
Q

What is the refractory period?

A

The period during/right after AP that the neuron cannot fire again

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26
Q

Are there more VG channels or leak channels in the membrane?

A

Voltage-gated channels

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27
Q

During the refractory period, the Na+ channels are ____________ and the K+ channels are _________

A

Closed; open

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28
Q

Repolarization restores ________ conditions

A

electrical

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29
Q

Na+/K+ pumps restore _____________ conditions

A

Ionic

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30
Q

What are the four principles of action potential?

A

All-or-none principle, refractory period, forward propagation, and rate code

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31
Q

What is the All-or-None principle?

A

An AP either happens completely, or it does not happen at all

32
Q

All APs are the same __________

A

Height, shape, and size

33
Q

What is the Refractory Period Principle?

A

Cause by K+ continuing to leave and Na+ VGs not being able to open

34
Q

Absolute Refractory

A

Starts at peak and lasts until returned to RMP

35
Q

Relative Refractory

A

A period of time when a neuron is less likely to send another AP

36
Q

What can make a neuron fire during a Relative Refractory period?

A

A strong stimulus

37
Q

Forward movement principle

A

Action potentials can only move forward on an axon; period behind them in refractory

38
Q

What is the Rate Code Principle?

A

There are no strong or weak APs; APs remain constant

39
Q

What increases when the stimuli increase?

A

Stronger stimuli causes AP to happen more frequently

40
Q

Where does AP propagation start?

A

The Axon Hillock

41
Q

+ charges move ________ the axon

42
Q

The role of myelin

A

Increases the speed of action potential propogation

43
Q

What two things does the rate of AP propagation depend on?

A
  1. Axon diameter
  2. Degree of myelination 3
44
Q

How does axon diameter change speed?

A

Larger diameter fibers have faster impulse conductions

45
Q

How does the degree of myelination change speed

A

Electrotonic conduction in nonmyelinated axons is slower than saltatory conduction in myelinated axon

46
Q

Action potential in nonmyelinated axons propagates by ________________

A

Passive Depolarization (electronic conduction)

47
Q

Myelin sheaths ________ and prevent __________ of charge

A

insulate; leakage

48
Q

Saltatory conduction occurs only in

A

myelinated axons

49
Q

Nodes of Ranvier

A

gaps in the myelin

50
Q

What is concentrated at Nodes of Ranvier

A

Vg Na+ channels

51
Q

Electrical signals appear to ________ rapidly from gap to gap

52
Q

What factors affect AP propagation?

A
  1. Decay
  2. Resistance to the flow of ions
  3. Capacitance
53
Q

What is Decay? What causes decay? How can we fix decay?

A

Loss of signal
Number of leak channels
Add myelin to block

54
Q

What is resistance to the flow of ions?

A

How difficult it is for ions to move

55
Q

More decay =

A

more loss of signal

56
Q

More channels open =

A

less membrane resistance

57
Q

Membrane resistance is

A

the number of open channels

58
Q

Inter resistance relies on

A

the diameter of the axon

59
Q

larger axons have (less/more) internal resistance

60
Q

Faster velocity is from

A

higher membrane resistance, lower internal resistance, and lower membrane capacitance

61
Q

Myelin (increases/lowers) capacitance

62
Q

Larger diameters have a ______ internal resistance and smaller diameters have a _______ internal resistance

A

lower; higher

63
Q

Capacitance

A

Build up of - charges on the inside membrane due to the close proximity of + and - charges

64
Q

Myelin increases/decreases capacitance

65
Q

How does myelin affect AP conduction velocity and how does this occur?

A

Speeds up conduction velocity; insulates the axon and reduces leakage.

66
Q

AP propagation in myelinated axon is ____________ than unmyelinated axons

A

100x faster

67
Q

At -70, Na+ VG are _______ and K+ VG are ________

A

closed; closed

68
Q

At -55mv, Na+ VG are ______ and K+ VG are _____

A

open; closed

69
Q

At +30mv, Na+ VG are ______ and K+ are ______

A

plugged by the ball and chain; open

70
Q

Hyperpolarization occurs because

A

K+ VG channels are slow closing so more K+ flows out making it more negative than RMP

71
Q

Simple diffusion is of

A

gasses and lipids

72
Q

Facilitated diffusion is through

A

ion channels

73
Q

The only factor that the Nernst equation focuses on is

A

concentration

74
Q

The factors that the GHK focuses on are

A

concentration and permeability

75
Q

Membrane resistance is how easy it is to (enter/leave) the axon

NEU211 Intro to Neuro (13 decks)

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