Final answer:
The electrical signal spreads from cardiac muscle cell to cell through a series of depolarization and repolarization events.
Step-by-step explanation:
The electrical signal spreads from cardiac muscle cell to cell through a series of depolarization and repolarization events. The depolarization wave begins at the sinoatrial (SA) node, the heart's natural pacemaker, located near the wall of the right atrium.
From there, the electrical signal travels to the atrioventricular (AV) node, between the right atrium and right ventricle. It then passes through the bundle of His, the bundle branches, and the Purkinje fibers, ultimately spreading across the ventricular myocardium and causing the ventricles to contract.