Final answer:
The Sinoatrial node (SA node) is where the electrical impulse that governs heart rate and rhythm originates. It acts as the heart's pacemaker. The atrioventricular node (AV node) has the slowest rate of firing, allowing time for the atria to empty before the ventricles contract.
Step-by-step explanation:
The correct option : c
The electrical impulse that governs heart rate and rhythm originates from the Sinoatrial node (SA node). This component is the heart's natural pacemaker and it has the highest inherent rate of depolarization. The SA node begins the sinus rhythm, which is the normal electrical pattern that leads to the contraction of the heart. The electrical impulses start at the SA node, travel through the atria, and reach the atrioventricular node (AV node) where there's a brief pause. This allows the atria to completely empty into the ventricles. After this pause, the electrical signal continues to the bundle of His, then to the left and right bundle branches, and ends at the Purkinje fibers, which trigger ventricular contraction.
Regarding the component with the slowest rate of firing in the heart conduction system, it is the atrioventricular node (AV node). The AV node introduces a delay in the electrical signal, taking approximately 100 ms to pass through, which ensures the atria have time to empty their blood into the ventricles before the ventricles contract.