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10 Cards in this Set

  • Front
  • Back
Where do pacemaker potentials occur normally?
Sinoatrial node
AV node
His Purkinje system
What is the normal pacemaker of the heart
The SA node.
What is the normal rate of pacemaker potentials?
60--100 potentials/min
What are the latent pacemakers in the heart?
AV node and His-purkinje system.
When might latent pacemakers take over for the main pacemaker?
When the SA node is suppressed
What is unique about the pacemaker action potential?
It has an unstable resting potential that exhibits Phase 4 depolarization causing automaticity.
What phases are not present in the pacemaker potential?
Phases 1 and 2 are not present.
What happens during Phase 0, 3, and 4 of the pacemaker potential?
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).
What is the name of the current that accounts for pacemaker activity?
(I f)
What turns on the current that accounts for the pacemaker activity?
Repolarization of the membrane potential in the preceding action potential turns on (I f).