Which node is known as the pacemaker of the heart?

The sinoatrial (SA) node is known as the pacemaker of the heart because it initiates the electrical impulses that stimulate heartbeats. This small bundle of specialized cardiac muscle cells located in the right atrium generates impulses that prompt both atria to contract, effectively controlling the rhythm and rate of the heartbeat. The SA node sets the pace for the entire heart, typically firing at a rate of 60 to 100 beats per minute in a resting adult, which influences the overall heart rate.

Unlike other structures such as the atrioventricular (AV) node, which serves to delay impulses to ensure that the ventricles fill properly, or the Bundle of His and Purkinje fibers, which are responsible for conducting the electrical signals throughout the ventricles, the SA node is primarily responsible for the automatic initiation of the cardiac cycle. Thus, its role as the natural pacemaker is critical in maintaining normal heart rhythm and function.