Automatic electrical discharges in the myocardium normally begin within which of the follow-ing?
a. Bundle of His c. Bachmann's bundle
b. Sinoatrial node d. Atrioventricular node
ANS: B
The sinoatrial node , as well as the atrioventricular node, normally have action potentials that differ from those of other excitable cells of the heart. Depolarization of the sinoatrial node initi-ates the heartbeat by triggering a wave of excitation that spreads through the right and left atria as it moves toward the atrioventricular node.
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