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MSK Exam II > Resting Membrane Potentials and Action Potentials > Flashcards

Resting Membrane Potentials and Action Potentials Flashcards

1
Q

Excitatory cells start in a non-excited state with a __________ voltage on the interior of the cell relative to the exterior

A

Negative

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2
Q

Excitatory cells such as muscles and neurons transmit electrochemical impulses at their ______

A

Membrane

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3
Q

What are the major players in the excitation of an excitatory cell?

A 
Intracellular space
Extracellular space
Sodium (Na+)
Potassium (K+)
Na+/K+ ATPase pump
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4
Q

Describe the relative concentrations of K+ and Na+ inside vs. outside the cell

A

Inside the cell: High K+, Low Na+

Outside the cell: Low K+, High Na+

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5
Q

What maintains the following ion concentrations?

Inside the cell: High K+, Low Na+

Outside the cell: Low K+, High Na+

A

Sodium/Potassium ATPase pump

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6
Q

What are the 2 forces acting at the cell membrane to maintain ion concentrations?

A

Electrical force

Diffusion force

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7
Q

What is primarily responsible for the resting membrane potential?

A

Permeability of the plasma membrane to potassium ions

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8
Q

In what 2 primary ways does potassium move across the membrane?

A

Na/K ATP pump

K+ leak channels

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9
Q

How many Na+ and K+ are exchanged, and in what direction, for each molecule of ATP at the Na/K ATPase pump?

A

3 Na+ OUT

2 K+ IN

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10
Q

T/F: potassium leak channels are often open at ALL times, and they permit mostly unregulated passage

A

True

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11
Q

Which are more abundant in the cell membrane: K+ leak channels or Na+ leak channels?

A

K+ leak channels are present at 100:1 ratio to Na+ channels

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12
Q

Overall, passively ___ is more likely to leave the cell than ____ to enter

A

K+; Na+

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13
Q

Resting membrane potential is typically between _____ and _____

A

-80 to -90 mV

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14
Q

Diffusion forces operate on a __________ gradient

A

Concentration

Ions will travel down this concentration gradient

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15
Q

Electrostatic forces are _______-based, and opposites attract

A

Charge

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16
Q

Diffusion force + electrostatic force = ___________ force

A

Electrochemical

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17
Q

During movement of cations/anions across the membrane, charge will change on either side and ___________ (slow down/speed up) the movement of cations/anions

A

Slow down

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18
Q

____________ _____________ opposes diffusion based on charge; this is th epoint that net flow of ioins = 0

A

Equilibrium potential

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19
Q

___________ _________ is when electrical and chemical forces are equal and no net movement occurs

A

Electrochemical equilibrium

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20
Q

The equilibrium potential of a system can be calculated in several ways. How would you calculate the equilibrium potential for a single ion?

A

Nernst Equation

Movement of Na alone = +66 mV

Movement of K alone = -91 mV

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21
Q

A change in resting potential of +6 mV represents a net ion ________

A

Efflux

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22
Q

A change in resting potential of -29 mV will result in a net ______ of ions

A

Influx

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23
Q

The equilibrium potential of a system can be calculated in several ways. How would you calculate the equilibrium potential for multiple ions?

A

Goldman Equation - takes into account different ion concentrations and permeability

This equation is also known as the Goldman-Hodgkin-Katz (GHK) Equation

24
Q

Removing which of the following ion channels from the plasma membrane of a neuron will have the greatest influence on disrupting resting membrane potential?

A. Sodium-Potassium ATPase
B. Potassium leak channels
C. Sodium leak channels
D. Voltage-gated sodium channels

A

B. Potassium leak channels

25
Q

Lowering resting membrane potential below the equilibrium potential for potassium will result in which of the following to occur?

A. More potassium will exit the cell
B. More potassium will enter the cell
C. There will be no change on potassium
D. More sodium will enter the cell

A

B. More potassium will enter the cell

26
Q

Decreasing the extracellular potassium concentration will result in which of the following changes to resting membrane potential?

A. Become more negative
B. Become more positive
C. No change
D. Make it easier to depolarize

A

A. Become more negative

27
Q

Resting membrane potential is around -85 mV in skeletal muscle.

____________ = deviation from 0 mV

_____________ = when membrane potential becomes LESS negative

______________ = when membrane potential becomes MORE negative

_____________ = when membrane potential is returning towards resting membrane potential

A

Polarization

Depolarization

Hyperpolarization

Repolarization

28
Q

A ________ _________ is a large depolarization that elicits further depolarization and complete reversal of membrane potential across the plasma membrane

A

Action potential

29
Q

T/F: Deviation from the resting membrane potential as well as the length of action potentials varies between cell types

30
Q

What are the 3 key properties of action potentials?

A

All-or-none

Propagated (self-reinforcing)

Non-decremental

31
Q

_________ _______ are changes in membrane potential that are SMALL and LOCAL. These can be excitatory or inhibitory.

A

Graded potentials

32
Q

The strength of the initial graded potential correlates with what?

A

The strength of the triggering event

[The stronger the triggering event, the more channels will open to change the polarity of the membrane]

33
Q

Why do graded potentials dissipate with distance?

A

Because K+ leak channels are basically always open

[Note that this will not happen with a sufficient stimulus]

34
Q

What are the 4 stages of an action potential? What numeric phases do these correspond with?

A

Resting (phase 4)

Depolarization (phase 0)

Repolarization (phase 3)

Hyperpolarization

35
Q

What stage of an action potential corresponds to the refractory period?

A

Hyperpolarization - due to overshoot, membrane potential will be lower than initial resting potential

36
Q

__________ = the membrane potential at which action potential will certainly occur

37
Q

Ion channels associated with initiating action potentials are mostly ________, meaning they do not require energy.

Non-gated channels = _______ channels that allow ions to move down their concentration gradient

A

Passive

Leak

38
Q

What aspect of an ion channel might restrict ion movement?

39
Q

What are the 4 types of gated ion channels?

A

Voltage-gated

Ligand-gated

Signal-gated

Mechanically-gated

40
Q

What 2 gates are present in the voltage gated sodium channel?

A

Activation gate - opens when threshold potential is reached

Inactivation gate - begins closing almost immediately to start repolarization process

41
Q

Once threshold potential has been reached and depolarization occurs, there is an increase in permeability of the membrane to _____ ions.

______-gated ion channels open rapidly. After minimial delay, these channels ______ automatically.

A

Na+

Voltage

Close

42
Q

Voltage gated Na channels have two gates: activation and inactivation. What are the 3 phases of opening these channels?

A

Resting = activation gate closed; inactivation gate open

Activation = activation gate opens during initial depolarization

Inactivation =inactivation gate closes rapidly after activation phase (cannot be moved until membrane potential returns to near resting)

43
Q

T/F: Voltage-gated Na+ channels operate on a negative feedback loop

A

False; they operate on a POSITIVE feedback loop

[local triggering event opens some channels - if the event is large enough, there will be a greater and wider area of increased membrane potential with more Na+ channels opening downstream]

44
Q

Voltage-gated Na+ channels operate on a positive feedback loop. When is this loop “broken”?

A

At +30 mV because at this voltage Na+ channels close

45
Q

Repolarization of the cell membrane occurs when voltage-gated Na+ channels are __________.

_________ leaks out still through leak channels.

Voltage-gated _____-channels SLOWLY open further increasing the membrane permeability to this ion.

A

Closed

Potassium

K+

46
Q

How are voltage-gated K+ channels different from K+ leak channels?

A

Voltage-gated K+ channels have SELECTIVITY and the ability to CLOSE

47
Q

During hyperpolarization phase of the action potential, it is more difficult to stimulate a subsequent action potential due to the _________ period

A

Refractory

48
Q

During what type of refractory period are Na+ channels either open or the inactivation gate is closed and cannot re-open, thus another action potential CANNOT be generated?

A

Absolute refractory period

49
Q

During which type of refractory period is the inactivation gate now open and the activation gate is closed, so an action potential MAY be generated but it requires a stronger stimulus?

A

Relative refractory period

[at this point, K+ permeability is still fairly high and overshoots the potassium leaving the cell so the membrane becomes slightly more negative than resting membrane potential. In addition, not all voltage-gated Na+ channels are in the same state at the same time yet, varying the potential response]

50
Q

__________ potential = membrane potential that elicits an action potential

51
Q

What 3 things occur at the threshold potential in terms of voltage-gated Na+ channel activation and inactivation gates, and voltage-gated K+ channel gates?

A
  1. Rapid opening of voltage-gated Na+ channel activation gates
  2. Slow closing of voltage-gated Na+ channel inactivation gates
  3. Slow opening of the voltage-gated K+ channel gates
52
Q

At threshold potential, permeability begins to change but at different rates. For the following, specify rapidly or slowly:

Na+ permeability increases ___________

K+ permeability increases ___________

Na+ permeability decreases _________

K+ permeability decreases __________

A

Rapidly

Slowly

Rapidly

Slowly

53
Q

Permeability is not to be confused with ___________, which refers to the charge moving through a membrane

A

Conductance

54
Q

What condition is characterized by periodic dips in blood potassium levels, triggering membrane hyperpolarization where it is harder to reach threshold but repolarization occurs more quickly?

A

Hypokalemic periodic paralysis (HypoPP)

55
Q

What condition is characterized by excessive levels of potassium in the blood coupled with the inability to compensate like a normal person would - leading to prolonged depolarization and absolute refractory periods?

A

Hyperkalemic periodic paralysis

56
Q

How are attacks of hyperkalemic periodic paralysis managed?

A

Mild exercise, potassium-wasting diuretics, and glucose consumption

MSK Exam II (20 decks)

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