The Sinoatrial Node is responsible for what aspect of the heart?

• A. Coordinating ventricular contraction
• B. Setting the rhythm and rate of the heart
• C. Delaying conduction through the AV node
• D. Generating ventricular escape rhythm

Answer: (B)

The Sinoatrial node acts as the heart's natural pacemaker, generating automatic electrical impulses that establish the heart's rhythm and rate. It fires spontaneously, typically at about 60–100 beats per minute in a healthy adult, setting the pace for the entire heart. That impulse then travels through the atria to the AV node, which provides a brief delay to allow proper filling, before driving the ventricles through the rest of the conduction system.

This is why it sets the rhythm and rate—the SA node is the starting point for cardiac electrical activity. It does not delay conduction—that function belongs to the AV node. It does not coordinate ventricular contraction directly—that role is handled by the ventricles’ conduction pathway after the impulse passes through the AV node. And ventricular escape rhythm is a backup mechanism that kicks in when the primary pacemakers fail, not the normal duty of the SA node.