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MSKI Final Exam material > Dr. Karius' Action Potential lecture > Flashcards

Dr. Karius' Action Potential lecture Flashcards

1
Q

Why do cells expand a huge amount of energy maintaining the membrane potential?

A

to store energy

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2
Q

What characteristics of the pore channel allow it to control flow?

A

charge of its amino acids
size of the pore
can open/close

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3
Q

pore channels can be controlled by

A

voltage changes
chemical binding
mechanical deformation

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4
Q

a “closed” channel has done what?

A

undergone a conformational change

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5
Q

inactivation and closure

A

inactivation is also a conformational change that cuts off pore movement but it’s not the same thing as closure because its not able to directly open from the inactivated state

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6
Q

The usual order for channels is

A

Open –> Inactivation —> Closed

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7
Q

What controls the direction in which ions flow?

A

the gradient

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8
Q

Voltage gated channels are used by

A

Na and K

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9
Q

ClC1 channels are used by

A

Cl- open at rest, closes with depolarization

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10
Q

K-leak channels are active when?

A

at rest

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11
Q

What happens to chlorine channels during depolarization?

A

they close

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12
Q

What channels are open at rest? What channels are closed at rest?

A

Na/K symporters, K leaky, and Cl- are all operational at rest

Na+ and K voltage gated channels are closed at rest

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13
Q 
K+ leaky channel
When open?
What opens/closes?
Ion?
Inactivation?
A

open at rest/always
constitutive
K
No inactivation

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14
Q

ClC1 channels

When open?
What opens/closes?
Ion?
Inactivation?

A

open at rest
depolarization closes
Cl
Maybe inactivation?

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15
Q

Voltage gated Na

When open?
What opens/closes?
Ion?
Inactivation?

A

closed at rest, open during action potentiall
Opens during depolarization
Yes can be inactivated

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16
Q

voltage gated K channel

When open?
What opens/closes?
Ion?
Inactivation?

A

Closed at rest, opens during action potential
Opens during depolarization
K
Yes can be inactivated

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17
Q

The single highest user of ATP in the body is

A

the 3Na/2K pump, huge amounts of energy are

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18
Q

A local response is the

A

subthreshold

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19
Q

what is a subthreshold response?

A

a membrane depolarization that doesn’t achieve threshold

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20
Q

a sub-threshold is graded

A

they get larger with each new stimuli

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21
Q

what happens to local potentials after the stimulus is achieved?

A

they die away

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22
Q

Local responses have what kind of characteristic the further away they get from the site of stimulation?

A

they decay

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23
Q

Definition of excitable cells =

A

cells in which an action potential can be induced

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24
Q

there are ____ changes responsible for closing/opening a pore channel

A

2: both sides have to undergo a conformational change

25
Q

“excitable cells”: definition is restricted to

A

neurons
skeletal muscle
cardiac muscle
smooth muscle

26
Q

parts of an action potential:

A

subthreshold–> action potential (Depolarization) –> Repolarization–> hyperpolarization

27
Q

After voltage gated ion channels are fully open, what two events occur?

A

sodium enters the cell and will make the Vm positive, overshooting the nernst potential

28
Q

what happens during repolarization?

A

Na gates become inactivated and K gates are opening

they open slowly
K leaves cell
the cell repolarizes

29
Q

how does the Na channel close?

A

repolarization has to achieve -90mV

30
Q

What are the ionic events that produce the rapid unsweep of the action potential, repolarization, and the re-establishment of the resting Vm?

rapid upsweep

A

this is depolarization

opening of voltage gated sodium channels allowing sodium influx

31
Q

What are the ionic events that produce the rapid unsweep of the action potential, repolarization, and the re-establishment of the resting Vm?

repolarization

A

opening of voltage gated sodium channels and K-efflux/inactivation of sodium channels

32
Q

What are the ionic events that produce the rapid unsweep of the action potential, repolarization, and the re-establishment of the resting Vm?

resting

A

Na/K ATPase re-establishes resting concentrations

33
Q

Threshold =

A

the Vm at which ALL the Na channels have opened

34
Q

How does an action potential’s “shape” change during stimulus?

A

it doesnt. it’s just all or nothing

35
Q

how can you increase or decrease the amount of Na going into a cell during an action potential?

A

you cant: you have to make new channels or change the Na concentration

36
Q

Refractory period….
ABSOLUTE refractory period
Relative Refractory period

A

the period after an action potential in which it is impossible or more difficult to elicit a second action potential

AR: impossible to get a 2nd AP. Na channels open but inactivated

RR: more difficult to get a 2nd ap, some Na channels back to closer state

37
Q

What is the role of the Na/K ATPase?

A

restablishes the resting gradient

38
Q

the absolute refractory period makes up what “chunk” of the action potential?

A

the subthreshold, the depolarizaation, and a large portion of the repolarization

39
Q

the relative refractory period makes up what portion of the action potential?

A

a chunk of the repolarization and the hyperpolarization period

40
Q

Why don’t sodium channels close immediately after depolarization?

A

because the Vm is +

41
Q

Voltage inactivation =

A

depolarization block

something is maintaining the Vm in (+) and it doesn’t get a chance to return to resting Vm

it’s more or less stuck in the AR stage

42
Q

Subthresholds versus action potential propagation

A

Subthresholds die away the further they get from the origin of stimulus

action potentials do NOT die away

43
Q

Propagation of the action potential (4 parts)

A

1) action potential goes along axon allowing Na influx
2) Na diffuses to other regions
3) those regions of the membrane are brought to threshold
4) action potential propagated

44
Q

bigger/more myelinated axons —->

A

faster the conduction

45
Q

Node of Ranvier

A

points where myelination are missing

46
Q

Where are the Na/K channels located on a myelinated axon?

A

at the nodes

47
Q

Myelin does what

A

it doesn’t allow the sodium to diffuse away, so it maintains the signal

48
Q

What happens to sodium in an axon without myelination?

A

the sodium can leak out

49
Q

subthreshold versus action potential: which is graded?

A

subthreshold, not AP

AP is All or None

50
Q

how do ST and AP change with time?

A

ST die away, AP do not have a change in amplitude

51
Q

how do ST and AP change with distance?

A

ST die away, APs do not have a change in amplitude

52
Q

Define the following:

Saltatory conduction

A

in myelinated neurons, the action potential appears to hop from node of ranvier to node with little loss of Sodium in between: VERY FAST

53
Q

Define the following:

Propagation

A

an action potential in one part of the membrane is sufficient to depolarize the neighboring membrane to threshold

54
Q

Define the following:

Depolarization block

A

External force causes membrane potential to remain depolarized for longer periods of time: voltage gated sodium channels “stuck” in the inactive state

55
Q

Define the time of the AR in an AP

A

beginning of AP to middle of repolarization

56
Q

Define the time of the RR in an AP

A

End of ARP to some time after end of AP

57
Q

RR and AR periods differ when they occur but also how they can be induced

A

during a AR a second AP cannot be induced no matter what

during a RR a second one can be induced with increasing stimulus

58
Q

Mechanism of AR versus RR

A

in AR, all votage gated Na channels are either open or inactive

in RR, enough voltage gated Na channels have moved from inactive to closed state for a second potential to be induced

MSKI Final Exam material (15 decks)

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