Which structure serves as the primary pacemaker of the heart?

The sinoatrial node, often referred to as the SA node, is recognized as the primary pacemaker of the heart due to its unique ability to generate electrical impulses that initiate the heartbeat. Positioned in the right atrium, just below the opening of the superior vena cava, the SA node has specialized pacemaker cells with automaticity, meaning they can depolarize spontaneously. This characteristic allows it to set the pace for the entire heart rhythm by sending out electrical signals that prompt the atria to contract and push blood into the ventricles.

The SA node typically generates impulses at a rate of 60 to 100 beats per minute under normal physiological conditions. This rate can be modified by autonomic nervous system influences, adjusting the heart rate according to the body’s needs, such as during exercise or rest.

In contrast, other structures such as the atrioventricular node, Bundle of His, and Purkinje fibers play secondary roles in the cardiac conduction system. The atrioventricular node acts as a gatekeeper that delays the impulse from the atria before it enters the ventricles, allowing for coordination of heart contractions. The Bundle of His and Purkinje fibers are responsible for conducting the impulses swiftly through the ventricles, ensuring efficient