What is the usual pacemaker of the heart?

The sinoatrial (SA) node is recognized as the primary pacemaker of the heart. It is located in the right atrium and has the ability to generate electrical impulses at a rate that determines the heart's rhythm. This node initiates the electrical signal that triggers each heartbeat, causing the atria to contract and push blood into the ventricles.

The SA node sets the pace for the entire heart, typically firing electrical impulses at a rate of 60 to 100 beats per minute in a resting state. This rhythmic electrical activity spreads through the atrial muscle, ensuring coordinated contraction of the atria.

Other components of the cardiac conduction system, such as the atrioventricular (AV) node, Purkinje fibers, and Bundle of His, play vital roles in conducting these impulses but do not serve as the primary pacemaker. The AV node, for instance, acts as a gatekeeper that allows impulses from the atria to pass to the ventricles after a brief delay. The Bundle of His and Purkinje fibers help spread the electrical impulses through the ventricles, facilitating their contraction. However, the initiation of the heartbeat primarily resides within the SA node, establishing it as the usual pacemaker of the heart.