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

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

Explanation:

The sinoatrial (SA) node, also known as the natural pacemaker of the heart, initiates the heartbeat. It is located in the posterior - wall of the right atrium, adjacent to the entrance of the superior vena cava. The atrioventricular node is involved in conducting electrical impulses from the atria to the ventricles. The epicardium is the outer layer of the heart wall. The internodal tracts are pathways for electrical conduction between the SA and AV nodes.

Answer:

D. sinoatrial node; superior vena cava