Final answer:
The AV node has the slowest conduction speed, while Purkinje fibers conduct impulses the quickest within the heart's conduction system. The Purkinje fibers have the slowest inherent firing rate, and the SA node has the fastest.
Step-by-step explanation:
Cardiac action potential conduction speed is slowest in the atrioventricular (AV) node and fastest in the Purkinje fibers system. The component of the heart conduction system with the slowest rate of firing is the Purkinje fibers, as it would fire at approximately 15-20 impulses per minute in the absence of upstream pacing from the sinoatrial node. In contrast, the sinoatrial (SA) node, or pacemaker, has the fastest inherent rate, reaching a threshold that would naturally initiate around 80-100 heart impulses per minute.
The conduction system's speed variation serves a critical purpose, with the AV node providing a delay to allow the atria to complete their contraction and effectively pump blood into the ventricles before the ventricular contraction begins. This orchestrated sequence of events ensures the effective pumping of blood throughout the body.