Impulse/signal starts at SINOATRIAL NODE (SA) located in the ceiling of the right atrium, and spreads across atria.
Impulse reaches ATRIOVENTRICULAR NODE (AV) in floor of right atrium next to left atrium septal wall. Cardiac cells that act like nerve cells, BUNDLE IF HIS extendsdown through septum and split into 3 BUNDLE BRANCHES at apex of heart. Cardiac musvle cells extend the whole way down; re very long!!
BUNDLE BRANCHES split into PURKINJE FIBERS. Fibers bump into individual cardiac muscle cells by poking into walls of ventricles.