What is the name of the heart's natural pacemaker that sets the rhythm of the heartbeat?

The heart’s natural pacemaker that sets the rhythm of the heartbeat is the sinoatrial node.

The sinoatrial node, or SA node, is a small region of specialized cardiac muscle in the upper wall of the right atrium, near the opening of the superior vena cava. Its pacemaker cells spontaneously generate electrical impulses, which spread through the atria and begin each heartbeat.

The signal then reaches the atrioventricular node, travels through the Bundle of His and bundle branches, and spreads through Purkinje fibers to make the ventricles contract. These structures conduct the signal but normally do not set the primary rhythm; the SA node fires fastest and therefore leads the system.

The SA node was identified by Arthur Keith and Martin Flack, whose discovery was published in 1907. Its intrinsic rate is faster than a normal resting pulse because the autonomic nervous system slows or accelerates it according to the body’s needs.