Final answer:
The secondary pacemaker for the heart is the atrioventricular (AV) node. It receives the impulse from the sinoatrial (SA) node and transmits it to specialized conducting cells within the interventricular septum.
Step-by-step explanation:
The secondary pacemaker for the heart is the atrioventricular (AV) node. It is a clump of myocardial cells located in the inferior portion of the right atrium within the atrioventricular septum. The AV node receives the impulse from the sinoatrial (SA) node, pauses, and then transmits it into specialized conducting cells within the interventricular septum. This coordinated transmission of electrical signals ensures that the heart contracts in a synchronized manner.