What is the pacemaker of the heart?

• A. Atrioventricular Node
• B. Sinoatrial Node
• C. Purkinje Fibers
• D. Bundle of His

Answer: (B)

The sinoatrial node in the right atrium acts as the heart’s natural pacemaker. It contains specialized pacemaker cells that fire spontaneously at the fastest rate, typically 60–100 beats per minute in a healthy adult, setting the pace for the entire heart. This rapid, regular impulse starts the heartbeat and travels through the conduction system to coordinate atrial and then ventricular contraction. If the SA node slows or fails, other parts of the conduction system can take over, but at a slower intrinsic rate (the atrioventricular node around 40–60 bpm). The Purkinje fibers and Bundle of His are crucial for transmitting impulses to the ventricles and coordinating their contraction, but they do not determine the heart’s basic pace.