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MSS - MSK Exam 2 > Membrane Electrophysiology: Action Potentials > Flashcards

Membrane Electrophysiology: Action Potentials Flashcards

1
Q

action potential

A

rapid change in membrane potential away from normal, negative resting voltage to positive voltate

followed by a return back to negative RMP

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2
Q

what is required of excitable cells?

A

ability to alter permeability

-gated channels exist in different activation states

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3
Q

leak channels

A

always open

unregulated ion flow

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4
Q

gated channels

A

typically ion specific

can be:
1 closed (but can be activated)
2 open
3 closed and inactivated

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5
Q

voltage-gated channels

A

respond to changes in membrane potential

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6
Q

depolarization

A

flow of + ions into cells

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7
Q

hyperpolarization

A

flow of + ions out of cell

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8
Q

polarization

A

either positive or negative (other than 0mV)

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9
Q

hypopolarization

A

less negative than resting

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10
Q

depolarization

A

loses negative polarity

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11
Q

repolarization

A

return to RMP

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12
Q

hyperpolarization

A

membrane more polarized than RMP

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13
Q

threshold

A

action potential only occurs if threshold is reached

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14
Q

ungated potassium channel

A

always open

K+ efflux

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15
Q

voltage-gated sodium channels

A

generation of action potential in n. and skeletal muscles

closed at RMP
open quickly then close and inactive

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16
Q

voltage gated potassium channels

A

closed at RMP

open slowly and slowly close

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17
Q

three phases of voltage-gated sodium channel

A

closed but capable of activation
-at RMP

open
-threshold to peak

closed and inactivated
-peak to resting

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18
Q

phases of voltage gated potassium channels?

A

closed or open

act slowly**

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19
Q

what generates action potential?

A

rapid opening of sodium followed by inactivation

slow opening of potassium

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20
Q

depolarization?

A

sodium into cell

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21
Q

repolarization?

A

potassium out of cell

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22
Q

hyperpolarization?

A

caused by the slow delayed potassium channels

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23
Q

threshold depends on what?

A

strength and duration of stimulus

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24
Q

initial depolarization

A

stimulus reaches threshold

  • sodium channels open
  • sodium influx, depolarized membrane
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25
Q

peak Na+ conductance

A

reached right before action potential peak
-at peak, many Na+ are open

however, Na+ influx is actually minimal as Vm becomes closer to ENa+

26
Q

early repolarization

A

voltage-gated potassium still opening and sodium are locking

potassium efflux repolarizes membrane

27
Q

peak K+ conductance

A

mid-repolarization

-force on K+ is lower as voltage is approaching EK+

however, efflux greater due to greater conductance

28
Q

Na/K ATPase

A

always gradually restoring RMP

29
Q

refractory period

A

key for ensuring unidirectional propagation***

time period after AP when subsequent AP cannot, or likely will not, be generated

30
Q

absolute refractory period

A

no AP, regardless of stimulus can trigger

result of sodium channnel h gates (inactivation)

31
Q

relative refractory period

A

AP can be produced if large stimulus

result of slow-closing K+ channels - hyperpolarization

32
Q

two implications for refractory periods?

A

prevents rebound effect

sets upper limit to AP firing frequency

33
Q

characteristics of action potential?

A

undiminished propagation that regenerates an identical AP

**all or none law

34
Q

nervous system interpretation of AP?

A

frequency and number of APs

35
Q

graded potentials

A

sub-threshold**

can be summed
-duration and strength depend on stimulus

decremental - spread but die out

ex/ EPSP, IPSP, receptor, end-plate at NMJ

no refractory

36
Q

axon hillock

A

where the action potentials are initiated (lowest threshold)

37
Q

contiguous conduction

A

local event opening adjacent channels down entire membrane

38
Q

saltatory conduction

A

**with myelinated axons

allows for impulse “jumping” - faster

39
Q

nodes or ranvier

A

where AP is generated in myelinated axon during saltatory conduction

40
Q

schwann cells

A

myelinate PNS

41
Q

oligodendrocytes

A

myelinate CNS

42
Q

myein

A

insulating resistance

43
Q

diameter and conduction velocity?

A

increased diameter causes increased velocity

**decreased internal resistance to flow (ohms law)

44
Q

synaptic cleft

A

where info transmitted cell to cell

45
Q

subsynaptic membrane

A

receptors

46
Q

two categories of synaptic communication

A

electrical and chemical

47
Q

electrical synapse

A

connexon channels of gap junctions

low resistance

reciprocal - both direction
rectifying - unidirectional

48
Q

chemical synapse

A

unidirectional

49
Q

ionotropic

A

rapid activation of receptor

-nicotinic ACh, NMJ

50
Q

metabotropic

A

slower activation of receptor

-G-protein liked receptor

51
Q

voltage gated calcium channels

A

responsible for an AP generating the influx of calcium

**calcium INFLUX

52
Q

calcium influx?

A

causes the neurotransmitter release

53
Q

convergence

A

single cell may be influenced by thousands of presynaptic cells (sensory)

54
Q

diverence

A

single axon terminal affects thousands of postsynaptic cells (motor)

55
Q

postsynaptic potential

A

get graded potential convergent at soma

56
Q

EPSP

A

excitatory postsynaptic potential

  • depolarizes/hypopolarizes membrane
  • always excitatory
57
Q

IPSP

A

inhibitory postsynaptic potential
hyperpolarizes membrane

always inhibitory

58
Q

excitatory signal?

A

sodium influx

potassium efflux

59
Q

inhibitory signal?

A

chloride influx

potassium efflux

60
Q

temporal summation

A

signals at same TIME

-frequency important

61
Q

spatial summation

A

signals in same SPACE (DISTANCE)

-multiple inputs combine to reach threshold

62
Q

cancellation

A

EPSPs and IPSPs cancel each other out

MSS - MSK Exam 2 (13 decks)

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