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MSK 2 > Membrane Potentials and Action Potentials > Flashcards

Membrane Potentials and Action Potentials Flashcards

1
Q

[K+] is higher inside or outside nerve cell?

A

inside

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2
Q

Is the outside or inside of the nerve membrane more negative?

A

inside

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3
Q

What does the Nernst equation calculate?

A

equilibrium membrane potential for ion

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4
Q

What is the Nernst equation?

A

61.5/z * log(concentration out/concentration in)

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5
Q

What does the Goldman-Katz equation examine?

A

membrane potential taking into accound multiple ions that are permeable to the plasma membrane using the concentration gradient, polarity, and permeability of multiple ions

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6
Q

K+ leak channels

A

allow K+ ions to “leak” outside of the cell

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7
Q

Na+/K+ ATPase (pump)

A

exchanges 3 Na+ outside ions for 2 K+ ions inside resulting more positive charge to the exterior of the cell

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8
Q

resting membrane potential

A

“polarized”

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9
Q

depolarization

A

membrane potential becomes more positive even reaching positive values

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10
Q

What is it called when membrane potential reaches positive values?

A

overshoot

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11
Q

hyperpolarization

A

membrane potential becomes more negative than RMP

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12
Q

afterhyperpolarization

A

where membrane becomes more negative than RMP following an action potential

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13
Q

threshold

A

the membrane potential required to initiate an action potential that is self-propagating and usually only approximately 15 mV more positive than RMP

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14
Q

self-propagating

A

once the action potential is initiated, it will travel throughout the entire plasma membrane without losing strength as it travels

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15
Q

subthreshold potentials

A

changes in membrane potential that do not reach threshold and decay in a predictable distance from the stimulus

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16
Q

graded potential

A

deflection in membrane potential is proportional to the strength of the stimulus as long as threshold is not reached

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17
Q

What phase are voltage gated Na+ channels important?

A

important in depolarization

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18
Q

voltage gated Na+ channels activation gate

A

closed at RMP but rapidly opens upon depolarization events that reach threshold (-70 to -50 mV) to activate channel allowing Na+ to enter cell

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19
Q

voltage gated Na+ channels inactivation gate

A

gate on interior of the cell that starts to slowly close upon a depolarization event that reaches threshold after a short delay, blocking Na+ entry to the cell. Will not open again until membrane potential reaches near or equal RMP.

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20
Q

What do high or low levels of Ca2+ extracellularly lead to in regard to membrane potential?

A

hypocalcemia leads to hyperexcitability (greater probability that voltage-gated Na+ channels will open)

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21
Q

tetrodotoxin (TTX)

A

inhibit voltage-gated Na+ channels

22
Q

saxitoxin (STX)

A

inhibit voltage-gated Na+ channels

23
Q

voltage-gated K+ channels

A

gate is closed at RMP but opens slowly upon activation during depolarization and aids in repolarization of membrane back to RMP along with the K+ “leak” channels

24
Q

voltage-gated Ca2+ channels

A

allow positive charge and Ca2+ ions to enter the cell

open slowly for a more sustained depolarization

25
Q

absolute refractory period

A

last from the initiation of the action potential to when the repolarization is generally complete, a second action potential cannot be initiated

26
Q

refractory periods

A

periods of time when an action potential cannot be generated or requires a greater stimulus to initiate a second action potential

27
Q

relative refractory period

A

occur following the absolute refractory period and require a stronger or longer minimal stimulus to initiate an action potential

28
Q

muscle (cardiac/skeletal) resting membrane potential

A

-80 to -90 mV

29
Q

smooth muscle resting membrane potential

A

-60 mV

30
Q

neuron resting membrane potential

A

-60 to -70 mV

31
Q

diffusion forces

A

chemical gradient based on concentration

32
Q

electrostatic forces

A

electrical gradient based on charge

33
Q

electrochemical forces

A

diffusion forces + electrical forces

34
Q

equilibrium potential

A

membrane potential when electrical and chemical forces are equal, no further movement occurs

35
Q

equilibrium potential of Na

A

+66 mV

36
Q

equilibrium potential of potassium

A

-91 mV

37
Q

driving force

A

resting membrane potential - [Eion]

38
Q

positive driving force

A

efflux of ions

39
Q

negative driving force

A

influx of ions

40
Q

Eion for K+

A

-91 mV

41
Q

Eion for Na+

A

+61.5 mV

42
Q

Eion for Ca2+

A

+123 mV

43
Q

Eion for Cl-

A

-66.4 mV

44
Q

What is the main contributor to resting membrane potential?

A

K+ leak channels

45
Q

What is the contribution of Na+ diffusion to membrane resting potential?

A

minimal due to low permeability at rest, 5mV positive contribution

46
Q

What is the contribution of Na+/K+ ATP pump to resting membrane potential?

A

minimal, 4 mV negative contribution

maintains ion concentration gradients

47
Q

gates of voltage gated Na+ channels at rest

A

activation gate closed

inactivation gate open

48
Q

gates of voltage gated Na+ channels during activation

A

activation gate opens during depolarization

49
Q

gates of voltage gated Na+ channels during inactivation

A

inactivation gate closes between 0 and +30 mV

50
Q

hypokalemic periodic paralysis (HypoPP)

A

periodic dips in blood K+ levels
drop triggers event, membrane hyperpolarized, harder to reach threshold
repolarization occurs more quickly

51
Q

hyperkalemic period paralysis

A

excessive levels of K+ in blood, unable to compensate
prolonged depolarization and absolute refractory periods
treatment: mild exercise, potassium wasting diuretics, glucose consumption

MSK 2 (15 decks)

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