The Sinoatrial Node is responsible for initiating the heartbeat.

• A. It conducts impulse to the ventricles
• B. It initiates the heartbeat
• C. It delays impulse between atria and ventricles
• D. It anchors valves

Answer: (B)

The key idea is that the heart’s natural pacemaker starts the heartbeat. The Sinoatrial node, located in the right atrium, contains pacemaker cells that spontaneously generate electrical impulses at a regular rate. This impulse sets the rhythm and triggers atrial contraction, then travels through the conduction system to stimulate the ventricles. Because of this initiating role, it defines the pace of the heartbeat.

Other parts of the conduction system handle different jobs. The impulse that moves toward the ventricles is carried onward after the SA node, so the SA node doesn’t directly conduct to the ventricles. The delay between atrial and ventricular activation is handled by the AV node, not the SA node. Valves aren’t anchored by the SA node; they’re held in place by other heart structures like connective tissue and chordae tendineae. So, saying the SA node initiates the heartbeat best captures its primary function.