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Block 5 > Phys: Membrane Potentials And Action Potentials > Flashcards

Phys: Membrane Potentials And Action Potentials Flashcards

1
Q

Ungated channels are…

A

selectively permeable to certain substances

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2
Q

Transport in ungated channels is determined by:

A

-size
-shape
-charge of channel
-ion

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3
Q

Gated channels:

A

-voltage
-ligand/chemical

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4
Q

Example of voltage gated channel:

A

Voltage gate Na+ channels

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5
Q

Examples of ligand/chemical channels:

A

nicotinic acetylcholine receptor channels

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6
Q

Active transport of Na+ and K+

A

NA+ is pumped out and K+ pumped in to maintain the concentration gradients between ECF and ICF

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7
Q

Simple diffusion and Na+ and K+ occurs vis which channels?

A

Leak channels

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8
Q

Simple diffusion of Na+ and K+

A

-K+ channels selectively permit passage of K+ across the membrane
-Na+ channels selectively permit passage of Na+ across the membrane

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9
Q

A diffusion potential is the…

A

Potential difference generated across a membrane when a charged solute diffuses down its [ ] gradient

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10
Q

A diffusion potential can be generated ONLY if…

A

The membrane is permeable to that ion

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11
Q

If a membrane were only permeable to K+ then…

A

K+ would diffuse down [ ] gradient until electrical potential across membrane countered diffusion

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12
Q

The electrical potential that counters net diffusion of K+ is called the…

A

K+ equilibrium potential

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13
Q

Ek =

A

-61 X log Ki/Ko

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14
Q

Na-K ATPase is necessary for resting membrane potential(RMP) allowing for ____ Na+ out and ___ K+ in makes inside more __________

A

3, 2, negative

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15
Q

If a membrane were permeable to only Na+ then…

A

Na+ would diffuse down its concentration gradient until potential across membrane counters diffusion

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16
Q

The electrical potential that counters net diffusion of Na+ is called the:

A

Na+ equilibrium potential

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17
Q

ENa =

A

-61 X log Nai/Nao

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18
Q

Membrane potential for K+

A

-94mV

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19
Q

Na+ membrane potential

A

+61mV

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20
Q

Vm value range

A

-90 to -70mV

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21
Q

Why is Vm so close to Ek?

A

The membrane is far more permeable to K+ than Na+

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22
Q

Goldman-Hodgkin-Katz equation calculates the…

A

Vm when more than one ion is involved

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23
Q

The resting membrane potential is closest to the equilibrium potential for…

A

The ion with the highest permeability

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24
Q

What does increasing K+ permeability have on Vm?

A

Will cause membrane potential to become more negative

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25
What effect does increasing Na+ permeability have on Vm?
Membrane potential will become more positive
26
What is the effect of high and low plasma potassium on threshold potential?
-high potassium levels depolarize the cell membrane bringing it closer to the threshold -low potassium levels hyperpolarize it, moving it further away from the threshold
27
What is the effect of high and low plasma potassium on membrane potential?
-high potassium brings the membrane potential closer to zero -low potassium moves it further away from zero
28
Terms for resting and action potentials:
-depolarization -hyper polarization -overshoot -repolarization -excitability -threshold
29
Overshoot is…
Positive to 0 mV
30
Repolarization:
process where a cell membrane potential returns to its resting negative state after experiencing a depolarization phase
31
Threshold
Membrane potential at which an action potential is triggered
32
An increase in extracellular [K+] increases the excitability of the cell becasue…
The resting membrane potential is closer to the threshold potential
33
What is the most common cause of muscle tetany?
Hypocalcemia
34
How does low calcium levels in blood cause tetany?
Low calcium increases excitability of nerve axons by causing sodium channels to open following very small increases in Vm
35
How do calcium ions affect Na channel?
-decrease in number of Ca ions reduces the threshold required to open sodium gate -threshold potential is more negative and closer to Vm when plasma calcium is low
36
Hyperkalemia is one of the deadliest electrolyte disorders becasue of….
Deadly cardiac arrhythmias
37
Initial treatment of hyperkalemia should be…
Intravenous administration of calcium
38
an action potential is a…
Regenerating depolarization of membrane potential that propagates along an excitable membrane
39
Propagates definition:
Conducted without decrement
40
Excitable definition:
Capable of generating action potentials
41
Action potential basics:
-all-or-nothing -constant amplitude (no summation) -initiated by depolarization -involves change in permeability -rely on voltage gated ion channels
42
Threshold voltage is usually…
15 to 13 mV positive to resting potential
43
Action potentials can be induced in nerve and muscle by______________________
Extrinsic stimulation
44
Fibers with _______ diameter conduct faster
Large
45
To find myelinated fiber velocity:
Mylinated Fiber diameter (mm) X 4.5 = velocity(m/s)
46
Velocity of unmyelinated fiber :
Unmyelinated fiber diameter = velocity
47
Function of action potentials:
-deliver sensory info to CNS -information coding -rapid transmission over distance -in non-nervous tissue, initiate cellular responses
48
Cellular responses that action potential scan control:
-muscle contraction -secretion
49
During upstroke of action potential:
-Na+ perm. Increases due to opening of Na+ channels -membrane approaches ENa
50
During downstroke of action potentials:
-Na perm decreases due to inactivation of Na+ channels -K perm increases due to opening of K+ channels -> mem potential approaches EK
51
After hyperpolarization of the membrane following an action potential…
increased K+ conductance due to delayed closure of K+ channels
52
Ion channel structure:
-proteins span membrane -have water filled channel than runs though protein
53
Ion channel properties:
-have conducting states and non-conducting states -transition between states = gating
54
Channels “gate” in response to:
-changes in membrane potential -occupation of receptor -mechanical forces
55
Permeability of axon membrane to ions is determined by:
Number of open channels
56
Ion channels are usually_____________________
Selectively permeable
57
Ion channels are selectively permeable to:
-specific ions -classes of ions
58
What does it mean to be permeable to classes of ions?
Some channels are selective to only cations over anions, for example
59
Ion channel gating refers to…
Transition between different states that reflect different conformational states of channel proteins
60
Activation gating transition:
Opening of channel when membrane is depolarized
61
Deactivation gating transition:
Closure of channel when membrane depolarizes
62
Depolarization causes:
-Na+ channels to activate -prevent inactivated channels from passing ions -K+ channels show activation but NOT inactivation
63
K+ channels only ____________ and the rate of opening is much ___________ than the Na+ channels
Activate, slower
64
Voltage gated channels are _______________ for most action potential
REQUIRED
65
If voltage gated channel is blocked….
No AP will occur (paralysis)
66
What two things can block AP?
-tetrodotoxin -lidocaine
67
Etraethylammonium (TEA) blocks the:
-voltage gated K+ channels -outward K+ current -repolarization
68
Refractory periods limit the…
Maximum frequency if action potentials
69
Absolute refractory peroid
-AP not possible due to volatile inactivation of Na+ channels -gates are in closed position until cell is repolarized back to resting potential and Na+ channels have recovered
70
Relative refractory period:
-greater than normal stimulus required to elicit AP -higher K+ conductance than whats present at rest -more inward current needed to bring membrane to threshold for next AP

Block 5 (46 decks)

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