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MSK 2 > Membrane Potential > Flashcards

Membrane Potential Flashcards

1
Q

muscle (cardiac skeletal)

A

-80 to -90 mv

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2
Q

smooth muscle

A

-60 mv

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3
Q

neurons

A

-60 to -70 mv

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4
Q

astroglia

A

-80 to -90 mv

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5
Q

erythrocytes

A

-9 mv

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6
Q

types of gated channels

A
  • voltage-gated
  • ligand-gated
  • signal-gated
  • mechanically-gated
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7
Q

electrochemical forces

A
  • diffusion forces
  • electrostatic forces
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8
Q

equilibrium potentil (Eion)

A
  • membrane potential when electrical and chemical forces are equal
  • no further movement occurs
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9
Q

equlibrium potential for Na+

A

+66 mv

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10
Q

equalibrium potential for K+

A

-91 mv

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11
Q

Nernst equation

A
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12
Q

Potassium (K+)

A

In: 150 mM

Out: 5 mM

E: -91 mv

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13
Q

Sodium (Na+)

A

In: 15 mM

Out: 150 mM

E: 61.5 mv

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14
Q

Calcium (Ca2+)

A

In: 0.0002

Out: 2

E: +123 mv

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15
Q

Chloride (Cl-)

A

In: 10 mM

Out: 120 mM

E: -66.4 mv

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16
Q

effect of increased extracellular K+ concentration

A

more positive RMP = easier to depolarize

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17
Q

effect of decreased extracellular K+

A

more negative RMP = more difficult to depolarize cell (cell is hyperpolarized and further from threshold)

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18
Q

insulin (effect on K+)

[Na-K-ATPase]

A

enhanced cell uptake

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19
Q

beta-catecholamines (effect on K+)

[Na-K-ATPase via + cAMP]

A

enhanced cell uptake

20
Q

alpha-catecholamines (effect on K+)

[opposite of beta]

A

impaired cell uptake

21
Q

acidosis (effect on K+)

[Donnan effect; inhibition of Na-K-ATPase]

A

impaired cell uptake

22
Q

alkalosis (effect on K+)

A

enhanced cell uptake

[“k is lo”]

23
Q

external potassium balance (effect on K+)

A

loose correlation

[ratio vs. total body K+ until severe states]

24
Q

cell damage (effect on K+)

A

impaired cell uptake

[release of intracellular contents]

25
Q

hyperosmolality (effect on K+)

A

enhanced cell efflux

[due to conctraction of ICF volume and increased K+]

26
Q

strenuous exercise (effect on K+)

A

enhanced cell efflux

[+ alpha-catecholamines]

27
Q

main contributor to resting m embrane potential

A

K+ diffusion potential

28
Q

minimal contribution to the RMP due to low permeability at rest (~5 mv positive)

A

Na+ diffusion

29
Q

minimal direct contribution to the RMP (~4 mv) with indirect contribution to maintain ion concentration gradients

A

Na+-K+ ATP pump

30
Q
  • permit mosty unregulated passage of ions (open always)
  • why K+ is more likely to passively leave the cell than Na+
  • main component in permeability of K+ to the plasma membrane
A

K+ leak channels

31
Q

are channels involved in membrane potential active or passive?

A

passive

32
Q

deviation from 0 mv

A

polarization

33
Q

when membrane potential becomes less negative

A

depolarization

34
Q

when membrane potential becomes more negaive

A

hyperpolarization

35
Q

when membrane potential is returning towards resting membrane potential

A

repolarization

36
Q
A

A. Resting - phase 4

B. Depolarization - phase 0

D. Repolarization - phase 3

E Hyperpolarization - refractor period)

37
Q

key players in action potential

A
  • Na+ ions
  • K+ ions
  • voltage-gated Na+ channels
  • voltage-gated K+ channels
  • K+ leak channels

* Ca2+ in certain cell types, such as cardiac

38
Q

identify the phases of opening for the activation & inactivation gates

A
  • resting: activation closed, inactivation open
  • activation: activation open during depolarizaton
  • inactivation: inactivation gate closed rapidly after activation phase
39
Q

when can the inactivation gate be opened?

A

when membrane potential returns to near resting

40
Q

2 things that contribute to repolarization

A
  1. potassium leaks out via K+ “leak” channels
  2. voltage-gated K+ channels slowly open to assist leak channels to increase membrane permeability to K+

(voltage gated Na+-channels are closed)

41
Q

what contributes to hyperpolarization/refractory period?

A

voltage-gated K+ close slowly and stay open too long causing too much K+ to leave (more difficult to stimulate subsequent AP)

42
Q

types of refractory periods

A
  • absolute refractory period
  • relative refractory period
43
Q
  • phase when Na+ channels are either open OR inactivation gate is closed/cannot reopen
    • no other AP can be generated
A

absolute refractory period

44
Q
  • phase when inactivation gate is now open and activation gate is closed
  • K+ permeablity fairly high and overshootsK+ leaving cell so membrane becomes slightly more negative than RMP
    • not all voltage-gated Na+-channels are in same state at same time yet varying the potential response
  • AP may be initiated but requires stronger stimulus
A

relative refractory period

45
Q

events of membrane permeability

A

A. Na+ permeability increased rapidly

B. K+ permeability increases slowly

C. Na+ permeability decreases rapidly

D. K+ permeability decreases slowly

46
Q
A

MSK 2 (12 decks)

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