Several nursing students are discussing cardiac conduction with their

Several nursing students are discussing cardiac conduction with their clinical instructor. When asked where a heart rate of 56 beats per minute most likely originates, the most informed student replies:

1. The atrioventricular (AV) node
2. The sinoatrial (SA) node
3. The Purkinje network
4. The bundle of His

ANSWER

ANS: 1
The conduction system originates with the sinoatrial (SA) node, the “pacemaker” of the heart. The SA node is in the right atrium next to the entrance of the superior vena cava. Impulses are initiated at the SA node at an intrinsic rate between 60 and 100 beats per minute. The electrical impulses are transmitted through the atria along intraatrial pathways to the atrioventricular (AV) node. The AV node mediates impulses between the atria and the ventricles. The intrinsic rate of the normal AV node is between 40 and 60 beats per minute. The AV node assists atrial emptying by delaying the impulse before transmitting it through the bundle of His and the ventricular Purkinje network. The intrinsic rate of the bundle of His and the ventricular Purkinje network is between 20 and 40 beats per minute.