Biology - The Cardiac Cycle

1. ATRIAL SYSTOLE

- Blood under low pressure flows into the atria via the pulmonary vein and vena cava

- As the atria fills, the increased pressure of blood against the atrioventricular valves pushes them open and blood begins to leak into the ventricles

- The atria walls contract, forcing open the actrioventricular valves and the rest of the blood into the ventricles

2. VENTRICULAR…