The pacemaker of the heart is called the

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

Answer: (B)

The sinoatrial node acts as the heart’s natural pacemaker. It sits in the right atrium and fires electrical impulses automatically and regularly, setting the pace for the heartbeat. This impulse starts in theSA node and travels through the atria to the atrioventricular node, then down the bundle of His and into the Purkinje fibers to trigger coordinated ventricular contraction. The other parts of the conduction system—the atrioventricular node, Purkinje fibers, and the bundle of His—serve to carry and coordinate the signal, but they do not initiate the heartbeat themselves. If the SA node’s pacing activity diminishes, other parts of the conduction system can take over, but usually at a slower rate.