thaler chapter 1

1   The Basics

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This physiologic delay in conduction is essential to allow the atria to finish contracting before the ventricles begin to contract. This clever electrical wiring of the heart permits the atria to empty their volume of blood completely into the ventricles before the ventricles contract. Like the sinus node, the AV node is also under the influence of the autonomic nervous system. Vagal stimulation slows the current even further, prolonging the delay, whereas sympathetic stimulation accelerates the current through the AV node.

AV node

A

Conduction pause at the AV node

B

( A ) The wave of depolarization is briefly held up at the AV node. ( B ) During this pause, the EKG falls silent; there is no detectable electrical activity.