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BRS Cardiology > Cardiac Action Potential > Flashcards

Cardiac Action Potential Flashcards

1
Q

What determines the resting membrane potential

A

conductance to K+

approaches K+ equilibrium potential

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2
Q

Inward current ____ the membrane potential

A

depolarizes;

brings in + charge

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3
Q

OUtward current ____ the membrane potential

A

hyperpolarizes

pumps out + charge

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4
Q

Resting membrane potential of ventricles, atria and purkinje system

A
  • 90 mV (approaches K+ equilibrium potential)
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5
Q

ventricles, atria and purkinje system

Phase 0

A

upstroke of action potential

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6
Q

ventricles, atria and purkinje system

Phase 0 is caused by ____

A

transient increase in Na+ conductance

inward Na+ current until approaches Na+ equilibrium potential at peak of AP

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7
Q

ventricles, atria and purkinje system

Phase 1 is the ____

A

brief period of initial repol

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8
Q 
ventricles, atria and purkinje system
Phase 1 (Initial repol) is caused by
A

outward current (by K+ out and decr Na+ in)

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9
Q

ventricles, atria and purkinje system

Phase 2 is the ___

A

plateau of the action potential

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10
Q 
ventricles, atria and purkinje system
Phase 2 (plateau) is caused by \_\_\_
A

transient incr in Ca2+ conductance (inward CA2+) and incr K+ out

outward = inward current

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11
Q

ventricles, atria and purkinje system

Phase 3 is the ____

A

repolarization

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12
Q

ventricles, atria and purkinje system

Phase 3 is caused by ___

A

decr Ca2+ inward, incr K+ outward
outward > inward
hyperpolarizes back toward K+ equilibrium potential

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13
Q

ventricles, atria and purkinje system

Phase 4 is the ___

A

resting membrane potential

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14
Q

ventricles, atria and purkinje system

Phase 4 is caused by ___

A

inward and outward currents equal

Vm approaches the K+ equilibrium potential

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15
Q

What is the SA node?

A

pacemaker of the heart

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16
Q

____ has an unstable resting potential and exhibits phase 4 depolarization

A

SA node

17
Q

Latent pacemakers are ___

A

AV node and His-Purkinje systems

18
Q

What are latent pacemakers

A

exhibit automaticity and override SA node if it is suppressed

19
Q

Order of rate of phase 4 depolarization

A

SA node > AV node > His-Purkinje

20
Q

SA node

Phase 0 is the ___

A

upstroke of the action potential

21
Q

SA node

What causes phase 0

A

incr in Ca2+ conductance (inward Ca2+ current) towards Ca2+ equilibrium potential

22
Q

SA node

Phase 1 and 2

A

NO PHASE 1 AND 2 IN SA NODE AP

23
Q

SA node

Phase 3 is the ___

A

repolarization

24
Q

SA node

What causes phase 3

A

incr in K+ conductance (outward K+) —> repolarization of membrane potnetial

25
Q

SA node

phase 4 is the ____

A

slow depolarization

26
Q

SA node

What causes phase 4

A

pacemaker activity of SA node
incr Na+ conductance (inward Na+)
turned on by repolarization

27
Q

AV node

Upstroke of AP is due to

A

inward Ca2+ current (like SA node)

28
Q

What is conduction velocity

A

time for excitation to spread throughout cardiac tissue

29
Q

what does conduction velocity depend on

A

size of inward current during upstroke of AP (larger inward current, higher conduction velocity)

30
Q

conduction velocity is fastest in ___ and slowest in ___

A

fastest in Purkinje

slowest in AV node for ventricular filling before ventricular contraction

31
Q

what is excitability

A

ability of cardiac cells to initiate AP in response to inward, depolarizing current

32
Q

What is absolute refractory period

A

from upstroke of AP and ends after plateau

NO AP CAN BE INITIATED EVER

33
Q

what is effective refractory period

A

conducted action potential cannot be elicited

slightly longer than the absolute refractory

34
Q

what is the relative refractory period

A

after absolute refractory period when repol almost complete

when an AP can be elicited but more than usual inward current required

BRS Cardiology (9 decks)

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