Which component of the heart conduction system initiates each heartbeat?

The component of the heart conduction system that initiates each heartbeat is the sinoatrial (SA) node. This specialized group of cells, located in the right atrium of the heart, functions as the heart's natural pacemaker. It generates electrical impulses that propagate throughout the heart, leading to the contraction of the atria and ultimately stimulating the ventricles to contract as well.

The SA node establishes the rhythm of the heartbeat by setting the pace for the entire cardiac cycle. Its depolarization triggers the atrial contraction, then the electrical signal travels to the atrioventricular (AV) node, then to the Bundle of His, and finally to the Purkinje fibers, which distribute the impulse throughout the ventricles and cause them to contract.

This sequence of electrical conduction maintains a coordinated and efficient contraction of the heart muscle, ensuring blood is effectively pumped throughout the body. The dominance of the SA node in controlling the heart rate underscores its critical role in normal cardiac function.