Final answer:
The Bundle of His picks up the signal from the AV node. It then transmits this signal through the bundle branches and finally to the Purkinje fibers, which cause ventricular contraction. The AV node fires at the slowest rate in the heart's conduction system.
Step-by-step explanation:
The signal from the AV node (atrioventricular node) is picked up by the Bundle of His (atrioventricular bundle). From there, it is then transmitted through the bundle branches and into the Purkinje fibers, which spread throughout the ventricles and trigger the ventricles to contract. The component of the heart conduction system with the slowest rate of firing is the atrioventricular node, as it allows for the delay that permits the atria to empty their blood into the ventricles before ventricular contraction.