Where is the pacemaker of the heart located?

• A. Purkinje Fibers
• B. QT Interval
• C. Segment
• D. SA Node

Answer: (D)

The heart’s natural pacemaker is the Sinoatrial (SA) node, and it’s located in the right atrium near the opening of the superior vena cava. This small cluster of pacemaker cells fires spontaneously, setting the rate and rhythm of the heartbeat. Its location allows the impulse to spread quickly across the atria, initiating atrial contraction, before traveling to the AV node and on to the ventricles.

This is the best choice because the SA node is specifically the tissue responsible for initiating the heartbeat. Purkinje fibers are part of the conduction system that relay the impulse to the ventricles but do not set the pace. The QT interval and a segment are ECG terms, not anatomical pacemaker tissue.