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10 Cards in this Set
- Front
- Back
Where do pacemaker potentials occur normally?
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Sinoatrial node
AV node His Purkinje system |
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What is the normal pacemaker of the heart
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The SA node.
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What is the normal rate of pacemaker potentials?
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60--100 potentials/min
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What are the latent pacemakers in the heart?
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AV node and His-purkinje system.
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When might latent pacemakers take over for the main pacemaker?
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When the SA node is suppressed
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What is unique about the pacemaker action potential?
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It has an unstable resting potential that exhibits Phase 4 depolarization causing automaticity.
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What phases are not present in the pacemaker potential?
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Phases 1 and 2 are not present.
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What happens during Phase 0, 3, and 4 of the pacemaker potential?
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Phase 0= Upstroke, caused by an increase in Ca+ conductance which allows an inward Ca+ current to depolarize the membrane toward the Ca+ equilibrium potential(I Ca).
Phase 3= Repolarization, caused by an increase in K+ conductance resulting in an outward K+ current(I k). Phase 4= Slow depolarization caused by an increase in Na+ conductance, resulting in an inward Na+ current(I f). |
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What is the name of the current that accounts for pacemaker activity?
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(I f)
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What turns on the current that accounts for the pacemaker activity?
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Repolarization of the membrane potential in the preceding action potential turns on (I f).
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