What is the primary electrical impulse within the heart, typically firing 60-100 beats per minute?

• A. AV node
• B. Atrioventricular junction
• C. Sinoatrial node
• D. Purkinje fibers

Answer: (C)

The heart’s rhythm is set by its natural pacemaker. The sinoatrial node, located in the right atrium, automatically fires an electrical impulse at about 60–100 beats per minute in a healthy adult. This impulse sets the pace for the heart, causing atrial contraction as it spreads through the atria, then travels to the atrioventricular node for a brief delay that allows the ventricles to fill, and finally moves through the His-Purkinje system to cause ventricular contraction. The AV node and Purkinje fibers are crucial for conduction, but they do not establish the normal rate—the SA node does. If the SA node fails, secondary pacemakers can take over at slower rates, but the typical primary driver remains the sinoatrial node.