Final answer:
The sinoatrial (SA) Node, also known as the heart's pacemaker, initiates the sinus rhythm that controls the heartbeats by sending electrical signals through the heart.
Step-by-step explanation:
The sinoatrial (SA) Node is also known as the pacemaker of the heart. This specialized clump of myocardial conducting cells is located in the superior and posterior walls of the right atrium, close to the orifice of the superior vena cava. The SA node has the highest inherent rate of depolarization and sets the pace for the heart by initiating the sinus rhythm. The sinus rhythm is the normal electrical pattern that results in the heart's contraction. This node commands the beat of the heart, ensuring a regular and coordinated heartbeat by sending electrical signals first to the right and left atria, and then to the atrioventricular (AV) node, followed by the ventricles.