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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
What is the refractory period?
The period during/right after AP that the neuron cannot fire again
26
Are there more VG channels or leak channels in the membrane?
Voltage-gated channels
27
During the refractory period, the Na+ channels are ____________ and the K+ channels are _________
Closed; open
28
Repolarization restores ________ conditions
electrical
29
Na+/K+ pumps restore _____________ conditions
Ionic
30
What are the four principles of action potential?
All-or-none principle, refractory period, forward propagation, and rate code
31
What is the All-or-None principle?
An AP either happens completely, or it does not happen at all
32
All APs are the same __________
Height, shape, and size
33
What is the Refractory Period Principle?
Cause by K+ continuing to leave and Na+ VGs not being able to open
34
Absolute Refractory
Starts at peak and lasts until returned to RMP
35
Relative Refractory
A period of time when a neuron is less likely to send another AP
36
What can make a neuron fire during a Relative Refractory period?
A strong stimulus
37
Forward movement principle
Action potentials can only move forward on an axon; period behind them in refractory
38
What is the Rate Code Principle?
There are no strong or weak APs; APs remain constant
39
What increases when the stimuli increase?
Stronger stimuli causes AP to happen more frequently
40
Where does AP propagation start?
The Axon Hillock
41
+ charges move ________ the axon
Down
42
The role of myelin
Increases the speed of action potential propogation
43
What two things does the rate of AP propagation depend on?
1. Axon diameter 2. Degree of myelination 3
44
How does axon diameter change speed?
Larger diameter fibers have faster impulse conductions
45
How does the degree of myelination change speed
Electrotonic conduction in nonmyelinated axons is slower than saltatory conduction in myelinated axon
46
Action potential in nonmyelinated axons propagates by ________________
Passive Depolarization (electronic conduction)
47
Myelin sheaths ________ and prevent __________ of charge
insulate; leakage
48
Saltatory conduction occurs only in
myelinated axons
49
Nodes of Ranvier
gaps in the myelin
50
What is concentrated at Nodes of Ranvier
Vg Na+ channels
51
Electrical signals appear to ________ rapidly from gap to gap
jump
52
What factors affect AP propagation?
1. Decay 2. Resistance to the flow of ions 3. Capacitance
53
What is Decay? What causes decay? How can we fix decay?
Loss of signal Number of leak channels Add myelin to block
54
What is resistance to the flow of ions?
How difficult it is for ions to move
55
More decay =
more loss of signal
56
More channels open =
less membrane resistance
57
Membrane resistance is
the number of open channels
58
Inter resistance relies on
the diameter of the axon
59
larger axons have (less/more) internal resistance
less
60
Faster velocity is from
higher membrane resistance, lower internal resistance, and lower membrane capacitance
61
Myelin (increases/lowers) capacitance
lowers
62
Larger diameters have a ______ internal resistance and smaller diameters have a _______ internal resistance
lower; higher
63
Capacitance
Build up of - charges on the inside membrane due to the close proximity of + and - charges
64
Myelin increases/decreases capacitance
decreases
65
How does myelin affect AP conduction velocity and how does this occur?
Speeds up conduction velocity; insulates the axon and reduces leakage.
66
AP propagation in myelinated axon is ____________ than unmyelinated axons
100x faster
67
At -70, Na+ VG are _______ and K+ VG are ________
closed; closed
68
At -55mv, Na+ VG are ______ and K+ VG are _____
open; closed
69
At +30mv, Na+ VG are ______ and K+ are ______
plugged by the ball and chain; open
70
Hyperpolarization occurs because
K+ VG channels are slow closing so more K+ flows out making it more negative than RMP
71
Simple diffusion is of
gasses and lipids
72
Facilitated diffusion is through
ion channels
73
The only factor that the Nernst equation focuses on is
concentration
74
The factors that the GHK focuses on are
concentration and permeability
75
Membrane resistance is how easy it is to (enter/leave) the axon
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NEU211 Intro to Neuro (13 decks)

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