Cardiac Cycle

1) Ventricles are relaxed. The atria contract, decreasing the volume of the chamber & increasing the pressure inside the chamber. Pushes blood into the ventricles.

2) Atria relax. Ventricles contract increasing the pressure. Forces the atrioventricular valves shut. Pressure higher than aorta & pulmonary artery forces sino-lunar valves open, blood to arteries

3) Both ventricles/atria relax. High pressure in PA/A closes SL valves. Blood returns to the heart & fill atria again due to higher pressure in vena cava & PA. In turn increases the pressure of the atria. Ventricles relax and the AV valves open allows blood through

1) Ventricles are relaxed. The atria contract, decreasing the volume of the chamber & increasing the pressure inside the chamber. Pushes blood into the ventricles.

2) Atria relax. Ventricles contract increasing the pressure. Forces the atrioventricular valves shut. Pressure higher than aorta & pulmonary artery forces sino-lunar valves open, blood to arteries

3) Both ventricles/atria relax. High pressure in PA/A closes SL valves. Blood returns to the heart & fill atria again due to higher pressure in vena cava & PA. In turn increases the pressure of the atria. Ventricles relax and the AV valves open allows blood through