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?

A. The SA node does not delay impulses; this function belongs to the atrioventricular (AV) node, which slows conduction to allow the ventricles to fill with blood before contraction. Therefore, this statement is incorrect. B. The SA node is correct because it is known as the heart's primary pacemaker. It spontaneously generates electrical impulses that set the rhythm of the heartbeat, initiating atrial contraction and coordinating the overall cardiac cycle. Its automaticity allows the heart to maintain a consistent rate under normal conditions. C. The SA node does not directly transmit impulses to the Purkinje fibers; electrical conduction from the SA node travels first through the atria, then to the AV node, bundle of His, and finally the Purkinje fibers to cause ventricular contraction. This makes option C incorrect. D. The SA node is not a secondary pacemaker; it is the primary pacemaker of the heart. Secondary pacemakers, such as the AV node or Purkinje fibers, only take over if the SA node fails, making this statement incorrect.