Cardiac Cycle
![Picture](/uploads/5/7/8/3/5783824/3850624.gif?374)
Depolarization: Electrical Stimulation
Systole: Mechanical Contraction
Repolarization: Electrical Relaxation
RE=rest
Diastole: Mechanical Relaxation
Sites of Origin
![Picture](/uploads/5/7/8/3/5783824/636540.jpg?408)
Sinus (SA) node: natural pacemaker of the heart
Rate: 60-100 BPM
Atria
Atrioventricular (AV) node or Junction
Rate: 40-60 BPM
Ventricles
Rate: 20-40 BPM
Rate: 60-100 BPM
Atria
Atrioventricular (AV) node or Junction
Rate: 40-60 BPM
Ventricles
Rate: 20-40 BPM