Final answer:
The sinoatrial (SA) node is the natural pacemaker of the heart, located in the right atrium, it has the highest inherent rate of depolarization and initiates the sinus rhythm.
Step-by-step explanation:
The sinoatrial (SA) node is the natural pacemaker of the heart. It is a specialized clump of myocardial conducting cells located in the superior and posterior walls of the right atrium. The SA node has the highest inherent rate of depolarization and initiates the normal cardiac rhythm, known as the sinus rhythm, followed by contraction of the heart.