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NSCI 6112: Neuroscience > Ion Channels, Resting & Action Potentials > Flashcards

Ion Channels, Resting & Action Potentials Flashcards

1
Q

Take Homes of Ion Channels Presentation (5)

  1. Ion Channels = generate ____ membrane potential and action potential
  2. Nernst Equation = electrochemical _____ potential for an ion across cell membrane
  3. ______ Equation = steady-state potential for multiple ions across the cell membrane
  4. Resting membrane potential = ___mV in many neurons bc neurons are primarily permeable to ___
  5. Action Potential Propagation: Unmyelinated axons = ____ conduction; myelinated axons = _____ conduction
A
  1. Ion Channels = generate resting membrane potential and action potential
  2. Nernst Equation = electrochemical equilibrium potential for an ion across cell membrane
  3. Goldman-Hodgkin-Katz Equation = steady-state potential for multiple ions across the cell membrane
  4. Resting membrane potential = -70mV in many neurons bc neurons are primarily permeable to K+
  5. Action Potential Propagation: Unmyelinated axons = continuous conduction; myelinated axons = saltatory conduction
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2
Q

What are the 3 Gating mechanisms?

A
  1. voltage gated
  2. ligand gated
  3. mechanical stress gated
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3
Q

Selective ion permeability of voltage gated channels is it which 3 ions?

A

selective to K+, Na+ or Ca2+

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4
Q

Selective ion permeability of ligand gated channels is cation selective to ___, ___ and sometimes ___ while anion selective to ___.

A

cation selective K+, Na+, sometimes Ca2+

anion selective Cl-

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5
Q

Channelopathies are

A

genetic disorders affecting ion channels

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6
Q

What Na+ channel is strongly expressed in nociceptive DRG neurons?

A

NaV1.7

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7
Q

NaV1.7 mutations cause _____ of DRG neurons and ______

A

hyperexcitability; neuropathic pain

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8
Q

Nonsense mutations in NaV1.7 result in

A

complete inability to sense pain (channels not being expressed at all)

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9
Q

Delayed rectifier K+ channels open with ______ and close with ______

A

depolarization; repolarization

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10
Q

What generates the falling phase of the action potential?

A

Delayed rectifier K+ channels

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11
Q

What generates the resting membrane potential?

A

Leakage K+ channels

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12
Q

Leakage K+ channels ____ at the resting membrane potential

A

open

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13
Q

What channel inactivation (closing after opening) includes a “ball and chain” protein segment that causes inactivation recovery from inactivation only after neuron repolarizes?

A

Na+

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14
Q

Na+ channel gate ____ with depolarization

A

open

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15
Q

What channel generates the rising phase of the action potential?

A

voltage gated Na+

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16
Q

What are the types of Ca2+ channels? (voltage subsets)

A
  1. High Voltage
    a) L-type
    b) N-type
  2. Low Voltage
    c) T-type
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17
Q

T/F: In the Ca2+ channels, inactivation time varies based on type

A

true

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18
Q

L-type ca2+ channels are sensitive to _______ and are a part of excitation-contraction coupling in _____

A

dihydropyridines; skeletal muscle

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19
Q

N-type ca2+ channels has a transmitter that releases at the

A

synapses

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20
Q

High voltage activated Ca2+ channels are at a charge of ____ depolarization

A

-50mV

21
Q

Low voltage activated Ca2+ channels are at a charge of ____ depolarization

A

5-10mV

22
Q

Which 2 ions flow INTO the cell?

A

Na+ and Cl-

23
Q

Which 2 ions flow OUT OF the cell?

A

K+ and A-

24
Q

Ion gradients across cell membranes are maintained by what enzyme?

A

Na+/K+ ATPase

25
Q

What is the natural charge of the intracellular membrane?

A

-85mV

26
Q

The equilibrium potential for K+ is

A

negative

27
Q

In equilibrium potential, the membrane is permeable to ____ ion

A

one

28
Q

In equilibrium potential, the ion flux is driven in _____ direction by the ________ across membrane

A

one; chemical gradient

29
Q

In equilibrium potential, flux results in (2)

A
  1. charge difference

2. voltage across membrane

30
Q

In equilibrium potential, opposite ion flux is driven by

A

the membrane voltage

31
Q

Electrochemical equilibirum is achieved at the voltage where the 2 fluxes…

A

balance each other out

32
Q

What are the equilibrium potentials for K+ and Na+?

A

K+: -90mV

Na+: +50mV

33
Q

What equation tells you what the equilibrium potential is?

A

Nernst Equation

34
Q

Which leakage channels are ALWAYS open in neurons?

A

K+

35
Q

Why is the resting potential -70mV instead of -90mV?

A

Because other channels like Na+ and Cl- are open which make the resting membrane potential a little more positive than the K+ equilibrium potential

36
Q

Generation of the action potential is a

A

all-or-none event

37
Q

Resting membrane potential

A

voltage-independent gK; leakage K+ channels

38
Q

Rising phase

A

activation of gNa; voltage gated Na+ channels (2)

39
Q

Falling phase

A

inactivation of gNa and activation of gK; inactivation of voltage-gated Na+ channels and delayed rectifier K+ channels (3) and leakage K+ channels

40
Q

Action potential depolarization in one region spreads ______ to neighboring regions

A

passively

41
Q

Passive depolarization initiates

A

action potential in neighboring region

42
Q

Myelinated axons include nodes of Ranvier which are separated by

A

long stretches of myelin

43
Q

Myelin is formed by which glial cells? (2)

A

oligodendrocytes & Schwann cells

44
Q

What is the internodal distance of Nodes of Ranvier?

A

1-2mm

45
Q

Saltatory Conduction

A

action potential depolarization at one node spreads passively to neighboring node 1-2mm distance; rapid propagation velocity

46
Q

Equilibrium potential equation

A

Vion (mV) = 58/z x log x {ion}0/{ion}i

log(10) = 1
log(1) = 0
log (1/10) = -1

47
Q

Na+ equilibrium is ____ if there is a higher concentration of Na+ outside the cell than in

A

positive

48
Q

Why is it more difficult to generate a 2nd action potential immediately following the generation of an action potential?

A
  1. Na+ channels are inactivated and cannot open to depolarize the neuron
  2. Delayed rectifier K+ channels remain open, hyperpolarizing the cell
49
Q

What will happen to an action potential traveling down a myelinated axon when it encounters a demyelinated region of the axon?

A

block/slowing of action potential

example: Multiple Sclerosis

NSCI 6112: Neuroscience (10 decks)

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