Question

multiple choice question
the heartbeat is initiated by the specialized cardiac muscle cells of the ______ which are located in the posterior wall of the right atrium, adjacent to the entrance of the

• sinoatrial node; superior vena cava
• atrioventricular node; inferior vena cava
• internodal tracts; coronary sinus
• epicardium; sinus venosus

Explanation:

The sinoatrial (SA) node, often called the natural pacemaker of the heart, is located in the posterior - wall of the right atrium, adjacent to the entrance of the superior vena cava. It initiates the heartbeat by generating electrical impulses.

Answer:

A. sinoatrial node; superior vena cava