Final answer:
The normal pacemaker of the heart is the sinoatrial node, which initiates the normal rhythm of the heart's contractions. The atrioventricular node has the slowest rate of firing, allowing time for atria to pump blood before the ventricles contract.
Step-by-step explanation:
The normal pacemaker of the heart is the sinoatrial (SA) node. The SA node is a specialized clump of myocardial conducting cells located in the right atrium that initiates the sinus rhythm, or normal electrical pattern that governs the contraction of the heart. As for the component with the slowest rate of firing, it is the atrioventricular (AV) node. The AV node delays the electrical signal from the SA node, allowing the atria to complete pumping blood before the impulse is transmitted to the ventricles.