Final answer:
The specialized area of cardiac tissue, located in the right atrium of the heart, which initiates the electrical impulses that determine the heart rate (pacemaker) is called the Sinoatrial (SA) node.
Step-by-step explanation:
The specialized area of cardiac tissue, located in the right atrium of the heart, which initiates the electrical impulses that determine the heart rate (pace maker) is called Sinoatrial (SA) node. It is a 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 is known as the pacemaker of the heart.