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MSK Exam 2 > Resting Membrane and action potentials > Flashcards

Resting Membrane and action potentials Flashcards

1
Q

Resting ion conditions of a skeletal muscle cell

A

inside:
150mM K
15mM Na
0.001 Ca

outside:
5 mM K
150 Na
1 Ca

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2
Q

Resting membrane Potential is primarily due to?

A

the permeability of the Potassium Ions

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3
Q

What is the resting membrane potential for some cells

A 
Muscle (cardia/skeletal): -80 to -90
Smooth muscle: -60
Neurons: -60 to -70
Astrogila: -80 to -90
Erythrocytes: -9mV
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4
Q

What pumps and channels are important in maintain a resting membrane potential

A

Na/k ATPase
K leak channels

these are Ion channels that form gated pores

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5
Q

Na/K ATPase channel

A

maintains concentrations in proper place
exchanges 3 Na+ ions to the outside of cell in exchange for 2K+ ions to the inside of the cell

requires ATP

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6
Q

K+ leak channels

A

Open all the time

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

Passively move K+ is more likely to leave the cell than Na to enter

allows for K permeabillity to the plasma membrane

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7
Q

Forces acting on Ions to develop Membrane Potential

A

Diffusion forces: Chemical gradients
Electrostatic Forces: Electrical
charge base opposite attracts

These two make up the Electrochemical Forces

Equilibrium potential (Eion) Membrane potential when electrical and chemical forces are equal, no further movement occurs

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8
Q

Nerst Equation

A

61.5/z times the log( [X]out/[X]in)

used to calculate the equilibrium potential

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9
Q

Driving Force

A

Resting membrane potential Vm - Eion

this represents the net efflux

Driving force takes into account the electrical and chemical forces to predict movement of the ions

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10
Q

IONin is greater than the IONout
IONin is less thatn the IONout
If IONin is equal to the IONout

A

the log will be negative

the log will be positive

the log will be zero

Always take into account the ion charge (+/-)

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11
Q

At resting membrane why cant NA+ get into the cell if it has an influx driving force

A

Because the membrane is mostly impermeable to the NA+ at rest

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12
Q

Goldman Equation

A

This is an equation that helps us determine the membrane potential by taking into account all the different ion concentrations and permeabillity

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13
Q

What are the three main contributions to the resting membrane potential

A

Contribution of K+ Diffusion potential: this is the main contributor to resting membrane potential

Contribution of the Na+ Diffusion: very minimal due to low permeability at rest

Contribution of Na+/K+ ATP pump: Indirectly contribution to maintain ion concentration gradients

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14
Q

If the Resting membrane potential is more positive, does it make it easier to depolarize?

A

If the RMP is more positive, it is easier to depolarize because it is closer to the threshold

if the RMP is more negative, it males it harder to depolarize the cell, (hyperpolarized and further away from the threshold)

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15
Q

What are some factors that influence the Potassium Distribution that plays an important part in RMP

A 
Enhance cell uptake:
Insulin
B-Catecholamines
Alklosis
Hyperosmolality
Strenous exercise
Impair cell uptake:
A-Catecholamines
Acidosis
External potassium balance
Cell damage
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16
Q

Polarization

A

Deviation from 0 mV

17
Q

Depolarization

A

when membrane potential becomes less negative

this does not mean action potential because it needs to get to that threshold to get an action potential

18
Q

Hyperpolarization

A

when the membrane potential becomes more negative

19
Q

Repolarization

A

when membrane potential is returning towards resting membrane potential

20
Q

Key properties of action potentials

A

All or None
propagating or self reinforcing
non decremental

21
Q

Graded Potentials

A

Changes in membrane potential that are small and local
can be both excitatory or inhibitory

Graded potential dissipate with distance because K+ leak channels are always open

Dependant on the stimulus and radius

strength of initiation is correlated with the strength of triggering event

22
Q

Phases of Action Potentials: Resting phase

A

Phase 4

23
Q

Phases of Action Potentials: Depolarization

A

Phase 0

24
Q

Phases of Action Potentials: Repolarization

A

Phase 3

25
Q

Phases of Action Potentials: Hyperpolarization

A

Refractory period

26
Q

What are the key players in an action potential

A 
Na+ ions
K+ ions
Voltage-gated Na+ channels
Voltage-gated K+ channels
K+ leak channels

Ca+ are important in some cell types

27
Q

How do the Voltage Na+ gates work

A

Resting: the activation gate is closed and the inactivation gate is open

Activation: the activation gate opens during initial depolarization and Na+ comes into the cell

Inactivation: inactive gate closes rapidly after the inactivation phase after a certain period of time

this inactivation gate will stay closed until the membrane potential returns

28
Q

What is the positive Feedback loop of voltage gated Na+ channels

A

Local triggering even occurs which opens some channels and if the event is large enough there will be a great wide area of increased membrane potential

more Na+ channels open and more Na+ flows through

this whole process stops at +30 mv because the Na+ channels close

29
Q

What happens during the repolarization phase

A

Voltage gated Na+ channels are closed

Potassium leaks out still via the K+ leak channels

Voltage gated channels slowly open to further increase the membrane permeabillity to K+

this helps to repolarize the cell

30
Q

What happens during the Hyperpolarization phase

A

Voltage gated K+ channels stay open a little too long which causes the increased repolarization

THis makes it more difficult to stimulate the next action potential

this is considered the refractory period

31
Q

Absolute refractory period

A

Na+ channels are either open or the inactivation gate is closed and cannot reopen

Another action potential cannot be generated

(the mountain on the graph)

32
Q

Relative Refractory period

A

Inactivation gate is now open and activation gate is closed

K+ permeabillity is still fairly high so there is hyperpolarization of the resting membrane potential

Not all Na+ voltage gates are in the same state

An action potential can still happen at this time, but requires a stronger stimulus

33
Q

Hypokalemic Periodic Paralysis (hypoPP)

A

Periodic dips in blood K+ levels

Drops in blood K+ levels triggers events, but blood K+ levels are normal between attacks

Membrane hyperpolarized, harder to reach threshold
repolarization occurs more quickly

34
Q

Hyperkalemic Periodic Paralysis

A

Excessive K+ in blood

Prolonged action potential and absolute refractory periods lengthened

these can be managed by mild excersise, potassium wasting diruetics, and glucose consumption

MSK Exam 2 (19 decks)

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