Final answer:
The secondary pacemaker for the heart is the Atrioventricular (AV) node, which receives the electrical charge generated by the Sinoatrial (SA) node and spreads it to the ventricles.
Step-by-step explanation:
The secondary pacemaker for the heart is the Atrioventricular (AV) node. After the electrical charge generated by the Sinoatrial (SA) node causes the atria to contract, the charge reaches the AV node, where it pauses for approximately 0.1 second before spreading to the walls of the ventricles. From the AV node, the electrical impulse continues to the Bundle of His, then to the bundle branches and finally to the Purkinje fibers, which conduct the impulse from the apex of the heart up the ventricular myocardium, causing the ventricles to contract.