Final answer:
If the action potential generated at the SA node does not reach the Purkinje fibers, the heart's ventricles would not contract properly. However, the AV node or Purkinje fibers themselves can act as a backup pacemaker but will trigger contractions at a slower rate.
Step-by-step explanation:
The normal cardiac conduction pathway begins with an action potential generated at the sinoatrial (SA) node. This impulse travels across the atria causing them to contract (atrial systole), and then reaches the atrioventricular (AV) node where it pauses. This delay ensures that the atria have time to empty their blood into the ventricles. After the pause, the impulse travels through the bundle of His, the right and left bundle branches, and finally to the Purkinje fibers. The Purkinje fibers then conduct the impulse, causing the ventricles to contract in turn (ventricular systole). If the signal from the SA node fails to reach the Purkinje fibers, an alternative pacemaker, usually the AV node, may kick in at a slower rate, but if the AV node also fails, the Purkinje fibers themselves can initiate contractions, albeit at a much slower rate. Therefore, if the signal does not reach the Purkinje fibers, the result could be ventricular asystole and a failing of the normal heart rhythm.