A nurse is caring for a patient with an irregular heart rhythm and is reviewing the cardiac conduction system. How should the nurse explain the function and nickname of the sinoatrial (SA) node to the patient?

The SA node delays electrical impulses to allow ventricular filling before contraction.

The SA node is the heart's primary pacemaker that initiates electrical impulses to regulate heartbeat.

The SA node transmits impulses to the Purkinje fibers to directly cause ventricular contraction.

The SA node functions as the secondary pacemaker and only activates when the AV node fails