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Membrane Potentials Flashcards

1
Q

Have gates controlled by change in membrane potential

A

voltage gated channels

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2
Q

have gates controlled by the binding of a ligand such as a neurotransmitter

A

ligand-gated channels

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3
Q

the potential difference generated across a membrane when an ion diffuses down its concentration gradient

A

diffusion potential

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4
Q

the magnitude of a diffusion potential depends on what?

A

the size of the concentration gradient

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5
Q

what is the driving force of diffusion potential?

A

concentration gradient

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6
Q

what is diffusion potential measured in?

A

millivolts

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7
Q

Movement of an ion across the membrane is determined by what?

A

both by the concentration gradient and by the electrical potential difference across the membrane

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8
Q

estimates the equilibrium potential for a given ion

A

the nernst equation

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9
Q

what is the approximate concentration of Na+ in the ECF?

A

140 mM

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10
Q

what is the approximate concentration of Na+ in the ICF?

A

14 mM

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11
Q

what is the approximate concentration of K+ in the ECF?

A

4 mM

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12
Q

what is the approximate concentration of K+ in the ICF?

A

120 mM

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13
Q

what is the equilibrium potential for Na+?

A

+65 mV

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14
Q

what is the equilibrium potential for K+?

A

-95 mV

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15
Q

the driving force for net diffusion of ions must account for what?

A

both the concentration gradient and the electrical potential across the membrane

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16
Q

How do you calculate the net driving force?

A

[membrane potential (mV)]- [equilibrium potential for a given ion (mV)]

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17
Q

If the driving force is negative [membrane potential is more negative than the equilibrium potential for a given ion] what will happen?

A

cation will enter the cell, anion will leave the cell

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18
Q

if the driving force is positive, what will happen?

A

cation will leave the cell, anion will enter the cell

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19
Q

the activation gate of the Na+ channel in nerve is opened by what?

A

depolarization

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20
Q

What happens to the inactivation gate of the Na+ channel in depolarization?

A

it is closed

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21
Q

At rest, the nerve membrane is far more permeable to…?

A

K+ than to Na+

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22
Q

Makes the membrane potential less negative (the cell interior becomes less negative aka more positive)

A

Depolarization

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23
Q

makes the membrane potential more negative

A

hyperpolarization

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24
Q

the flow of positive charge into the cell

A

inward current

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25
inward current causes what?
depolarization
26
the flow of positive charge out of the cell
outward current
27
outward current causes what?
hyperpolarization
28
membrane potential at which the action potential is inevitable
threshold
29
portion of the action potential where the membrane is positive
overshoot
30
portion of the action potential where the membrane is actually more negative than at rest of hyperpolarized
undershoot
31
period during which another action potential cannot be elicited
absolute refractory period
32
period during which another action potential can only be generated with a stronger stimulus because the threshold has raised
relative refractory period
33
at rest, the activation gate is?
closed
34
at rest the inactivation gate is?
open
35
at the peak of the action potential, the slow inactivation gate will?
close
36
when the membrane potential has repolarized back to its resting level, the activation gate will be? and the inactivation gate will be?
the activation gate will be closed and the inactivation gate will be open
37
What affect does depolarization have on K+ channels?
slowly opens K+ channels and increases K+ conductance
38
What is repolarization caused from?
an outward K+ current
39
When the serum/blood K+ concentration increases, what happens to the K+ equilibrium potential and the resting membrane potential?
they become less negative
40
What happens to the inactivation gates on Na+ channels with hyperkalemia?
they are closed
41
a reduction in the serum/blood potassium concentration will do what to the cell membrane?
hyperpolarize it
42
the process that occurs when the cell membrane is held at a depolarized level such that the threshold potential is passed without firing an action potential
accommodation
43
if depolarization occurs slowly enough, the Na+ channels do what?
The Na+ channels close and remain closed
44
In accommodation, The upstroke of the AP will not be able to occur because?
there are not enough Na+ channels available to carry inward current
45
What effect does lidocaine have on action potentials?
Lidocaine will block voltage-gated Na+ channels and therefore the inward current of Na+ and the upstroke of the AP will not occur
46
the speed at which action potentials are conducted along a nerve or muscle fiber
conduction velocity
47
What two factors affect time constant?
membrane resistance and membrane capacitance
48
How does a high membrane resistance (Rm) affect time constant?
it will increase it; current does not readily flow 1
49
the ability of the cell membrane to store charge
membrane capacitance
50
what affect does a high membrane capacitance (Cm) have on the time constant?
it will increase it because injected current must first discharge the membrane capacitor before it can depolarize it
51
What are the cable properties?
Time constant and length constant
52
The length constant indicates what?
how far a depolarizing current will spread along a nerve
53
When will the length constant be longest?
when the diameter of the nerve is large (Ri is low and Rm is high)
54
What effect does increased nerve diameter have on internal resistance?
decreases internal resistance
55
What effect does myelination have on membrane resistance?
increases it
56
What effect does myelination have on nerve capacitance?
decreases it
57
Periodic breaks at regular intervals along the length of the myelin sheath covering an axon
Nodes of Ranvier
58
Is the membrane resistance high or low at nodes of ranvier?
low
59
the AP will seem to leap along the axon from node to node
saltatory conduction
60
Where are action potentials generated in myelinated nerves?
at the nodes of ranvier
61
Loss of the myelin sheath around nerves causes what?
a decrease in membrane resistance
62
What effect does a decrease in membrane resistance have on an AP?
current "leaks out" across the membrane during conduction of local currents
63
What are the signs and symptoms of MS?
weakness of the LEs, numbness, paresthesia, blurred vision, and pain with eye movements

MSK Final (16 decks)

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