Final answer:
The atrioventricular (AV) node is a group of cells in the heart's right atrium that plays a crucial role in the cardiac conduction system by delaying the electrical impulse from the sinoatrial (SA) node, allowing the atria to finish contracting before the ventricles begin. If the SA node fails, the AV node can serve as a secondary pacemaker.
Step-by-step explanation:
The atrioventricular (AV) node is a vital component of the cardiac conduction system. It is a clump of specialized myocardial conductive cells located in the inferior portion of the right atrium within the atrioventricular septum. The AV node receives electrical impulses from the sinoatrial (SA) node, which is the primary pacemaker of the heart, situated in the right atrium.
Upon receiving the impulse from the SA node, the AV node holds a critical pause to allow the atria to complete their contraction, thereby ensuring that blood is effectively pumped into the ventricles. This pause encompasses a delay of approximately 100 milliseconds due to the small diameter of the cells and less efficient conduction between nodal cells. Should the SA node fail to initiate an impulse, the AV node can act as a secondary pacemaker, capable of generating a slower heart rate to maintain a basic level of cardiac output.