1.2.2 OCR Cardiac Cycle

Ventricular diastole: Atria contract, ventricles relax

• The atria fills with blood, the pressure inside the atria is high enough for the AV valves to open.
• The atria contracts forcing the remaining blood to enter the ventricles.

Ventricular systole: Atria relax, Ventricles contract.

• Pressure is high inside the ventricles causing the AV valves to close to prevent backflow.
• Pressure builds up as ventricles contract forcing the semilunar valves to open.
• Blood flows out the heart through the pulmonary artery and aorta

Atrial Systole: Ventricles relax, Atria relax.

• The heart is now relaxed, so the volume is larger decreasing the pressure inside all the chambers.
• The Semi lunar valves close due to the high pressure in the pulmonary artery and aorta. This prevents backflow

Right side of the heart pumps DEOXYGENATED blood to the lungs.

The left side of the heart pumps OXYGENATED blood to the whole body..

Valves open ONE WAY only.

High pressure BEHIND the valves-open

High pressure INFRONT of the valves- close