16 Intro to Cardiac Electrophysiology Flashcards

1
Q

inward rectifier K currents work better at what membrane potential

A

more negative Vm

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2
Q

effective refractory period

A

too many Na channels still inactive for AP

inward current would be too small to spread to neighbors

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3
Q

are mostly depolarized by Ca2+ current rather than Na+ current

A

nodal cells(SA, AV)

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4
Q

describe adenosine/acetylcholine effects on nodal cells

A
  • *act on M2 receptors **
  • decreases cAMP, pacemaker(funny) current initiates at more negative/later potentials
  • decreased PKA activity means less Ca current

act on IKAdo/IKACh directly

  • increase K efflux making APs take longer
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5
Q

describe NE modulation of nodal cells

A
  • *increases cAMP**
  • makes pacemaker current initiate sooner during repolarization
  • indirectly activates Ca channels via PKA prodution
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6
Q

pacemaker current

A

Na and K; Na predominates allowing eventual threshold/AP generation

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7
Q

strategies for interrupting arrhythmias

A

increase threshold(decrease Na current)

extend refractory period(increase AP duration, decrease K current)

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8
Q

EAD vs DAD

A

EAD appear during normal repolarization prior to complete repolarization

  • most common in prolonged QT

DAD occur after max hyperpolarization

  • occur with high intracellular calcium(digitalis)
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9
Q

blocking of hERG channels is associated with what pathology?

A

long QT syndrome

hERG channels are K channels; less K current means longer time to repolarize

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