The Cardiac Cycle. Cardiac Cycle. The cardiac cycle is one complete heart beat – a contraction and relaxation of each heart chamber; 1 cycle = 0.8s 2 basic phases: Diastole: ventricles relax to fill with blood Systole: Ventricles contract to push blood into arteries.
1) Atria are relaxed and fill with blood
2) Atria contract and force blood into the ventricles through the AV valves
3) Ventricles contract forcing AV valves shut and SL valves open; blood moves into arteries
4) Ventricles relax, causing SL valves to snap shut
P wave: atrial contraction
QRS complex: ventricular contraction
T wave: recovery from contraction