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CV Quiz > Excitable Cells and AP > Flashcards

Excitable Cells and AP Flashcards

1
Q

resting membrane potential

A

negative value

excess of negative charges inside compared to outside

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2
Q

how does the electical gradient arise?

A
  1. large gradients of Na+ and K+
  2. relative permeability of the membrane to those ions
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3
Q

Nernst Equation

A

-60 x log [Xi/Xo]

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4
Q

what happens if increase extracellular K?

A

equilibrium potential will become less negative/depolarize

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5
Q

what happens if you increase intracellular K

A

eq potential will increase/become more negative

hyperpolarize

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6
Q

K equilibrium potential

A

-88 mV

more on inside than outside

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7
Q

equilibrium potential of Na

A

+60 mV

more on outside than inside

if suddenly very permeale to Na (AP) it moves very positive very fast

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8
Q

permeability to a given ion

A

depends n number of channels and conductance of channels

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9
Q

GHK equation

Goldman-Hodgkin-Katz

A

used to determine the potential across a cell’s membrane taking into acct all of the ions that are permeant

start w Nernst and add permeability factor for K

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10
Q

what happens when increase K permeability at rest

A

hyper polarizes

drives membrane potential closer to Keq (-88)

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11
Q

Na/K ATPase

A

ubiquitously expressed in cell membranes

maintains gradient of Na and K

3 Na out for 2 K in

energy consuming

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12
Q

Na/Ca exchanger

A

in muscle cells

3 Na in and 1 Ca out down electrochemical gradients

reversible dep on voltage

maintains low intracellular Ca2+ levels

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13
Q

Ca2+ pump

A

expressed in muscle cells

pumps Ca2+ out with ATP

maintains low intracelular Ca2+ levels

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14
Q

passive membrane resistors

A

ion channels

resist flow but allows it to move

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15
Q

passive membrane capacitor

A

stores charge

2 conductors sep by insulatior

con = ECF, ICF

ions = cell membrane

charge builds up and can store it

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16
Q

passive membrane as circuit

A
  1. current charges capacitor (+ to mem and displaces + on the other side
  2. current moves through both capacitor and ion channel (new SS - charges begin to leave through resistor)
  3. at SS, current moves only through channel (resisotor)

voltage change is linear and can be predicted by Ohm’s law

17
Q

ionic basis of action potential

A

increase Na+ perm - rushes in, increase voltage to positive

incrase K+ perm - brings gradually back to negative

K channel is delayed rectifier - voltage gated!

18
Q

depolarization

A

when sodium channels open

outward current (bc Na+ in)

19
Q

hyperpolarization

A

when K channels open

inward current repolarizes the membrane

20
Q

VG - Na channels

A

closed - open (Na in) - inactivated (stuck and can’t activate - have to repolarize to open) - closed

21
Q

VG - K channels

A

delayed rectifiers

single gate - open and closed

open SLOWER

activated at more depolarized P

stays open until back to resting membrane potential

22
Q

rising phages

A

FEED FORWARD

stim –> depol membrane –> Na channels open –> inward current –> depol mem further

23
Q

falling phase

A

depol membrnae –> open VG K+ channels –> repolarize membrane –> return to Vrest

24
Q

overshoot

A

voltage about 0 mV

25
Q

amplitude

A

voltage from V rest to peak

26
Q

threshold potential

A

voltage you begin to activate Na+ channels

27
Q

absolute refractory period

A

if deliver 2nd stim - get NOTHING

Na+ channels are inactivated - can’t be opened, no response until “closed”

28
Q

relative refractory period

A

get response but it’s blunted

cell has increased K+ permeability compared to rest - if fire Na+ channels, response will be smaller

29
Q

action potential conduction

A
30
Q

length constant

A

proportional to rm/ri

resistance - how currnet will spread and voltage will change

higher length constant - current can spread farther

31
Q

time constant

A

time at which voltage is 63% of max

increase membrane capacitance or resitance –> increased time constant

32
Q

inactive membrane

A

Na channels closed

33
Q

electrotonic spread

A

spread of electrotonic current to inactive membrnae brings inactive membrane to AP threshold

34
Q

r (i)

A

internal resistance - affects length constant (and therefore conduction velocity)

35
Q

r(m)

A

membrane resistances - affects length const and therefore conduction velocity

36
Q

factiors that influence conduction velocity

A

length const

time const

available Na current

37
Q

diameter of axon

A

increased diameter = really fast

decrease r(i) –> longer length constant

38
Q
A

CV Quiz (5 decks)

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