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MSK2 > Action Potentials > Flashcards

Action Potentials Flashcards

1
Q

Which ion channel has the greatest influence on resting membrane potential?

A

Potassium (K+) leak channels

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2
Q

What are electrochemical forces made of?

A

Diffusion and Electrical forces

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3
Q

Equilibrium potential

A

membrane potential when electrical and chemical forces are equal and there is no movement
DOES NOT EQUAL RESTING MEMBRANE POTENTIAL

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4
Q

Driving force

A

predicts the movement of ions (efflux or influx)

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5
Q

What channels influence resting membrane potentials but less than K+ leak channels?

A

NA+/K+ ATPase channels

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6
Q

Resting membrane potential is primarily caused by what?

A

From membrane permeability to K+ (very permeable to K+)

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7
Q

Ratio of Na+ to K+ pumped

A

3NA+ OUT and 2K+ IN (PUMP K IN)

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8
Q

Normal resting potential of skeletal/cardiac muscle?

A

-80 to -90 mV (about -85 mV average)

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9
Q

Normal resting potential of smooth muscle?

A

-60 mV

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10
Q

Normal resting potential for neurons?

A

-60 to -70 mV (about -65 mV average)

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11
Q

How do you calculate driving force?

A

Resting potential minus equilibrium potential of ion.
Positive value = Eflux
Negative value = Influx

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12
Q

Eq potential of K+

A

-91 mV (potassium Pit)

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13
Q

Eq potential of Na+

A

+61.5 mV (sodium shuttle)

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14
Q

Eq potential of Ca+?

A

+123 (Calcium denim)

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15
Q

Eq potential of chlorine?

A

-61.5 mV (Chlorine Cheshire)

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16
Q

When calculating the driving force of Na+ in skeletal muscle, you find the force to be negative indicating Influx. However, no influx occurs. Why?

A

The membrane is mostly impermeable to Na+!!

17
Q

Goldman Eq

A

accounts for different ion concentrations all at once… permiability

18
Q

Permiability of K+?

A

80-85%

19
Q

Permiability of Cl-?

A

10-12%

20
Q

Permiability of Na+?

A

1-2%

21
Q

Permiability of Ca++?

A

1%

22
Q

Cardiac glycoside drugs target what part of the membrane?

A

Na+/K+ ATP Pumps
minimal direct contribution to resting potential
4mV negative contribution
Indirectly contributes to maintain ion concentration gradients

23
Q

An increase of potassium (Hyperkalemia) outside of the cell causes what?

A

Depolarize…. resting membrane potential moves to the right and is more positive. Cell depolarizes and repolarizes more quickly with shorter refractory.

24
Q

A decrease of potassium (hypokalemia) outside of the cell causes what?

A

Hyperpolarization, resting membrane potential becomes more negative and moves to the left on the graph.

25
Q

What is the threshold for action potentials?

A

-55 mV

26
Q

Polarization

A

deviation from 0 mV

27
Q

All-or-none

A

the signal travels everywhere with the same intensity of threshold is met

28
Q

Propagation or self-reinforcing signal

A

Dissipation of signals… stronger near site of stimulus then decreases… ONLY OCCURS IF THRESHOLD IS NOT MET

29
Q

Action potential graph: Phase 4, Phase 3, Phase 0

A 
Resting = Phase 4
Depolarize = Phase 0
Repolarize = Phase 3
Hyperpolarize = refractory
30
Q

Describe what happens to voltage-gated Na+ ion channels when stimulated

A
  1. Resting: activation gate closed, inactivation gate open
  2. Activation: activation gate opens (these gates close at some point near threshold)
  3. Inactivation: inactivation gate closes quickly and does not re-open until membrane potential is nearly back to resting
31
Q

Which channels open slowly during activation?

A

Voltage-gated K+ channels slowly open and increase the permeability of K+. This allows the membrane to repolarize quickly.

32
Q

What causes hyperpolarization?

A

Voltage-gated K+ ion channels stay open a little too long which leads to hyperpolarization (absolute refractory period)

33
Q

Relative refractory period occurs when __?

A

Na+ channels have reset but K+ channels are still open. Another action potential can occur doing this time.

34
Q

How are hypERkalemic attacks managed?

A

Mild exerise, administer potassium-wasting diuretics, glucose consumption

MSK2 (4 decks)

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