The sequence of depolarization and repolarization produces the electrical signal that triggers the contraction on the heart and the ejection of blood. If all of the chambers contracted simultaneously, then blood couldn't circulation through the heart because the AV valves would protect against blood flow between the atria and ventricles. https://hubbardm011qer8.prublogger.com/29169001/the-5-second-trick-for-polarized-heart