heart and cardiac cycle

Question 1

Stage 1:

Answer 1

The Ventricles are relaxed, atria contract decreasing the vol of the chambers and increasing the pressure inside the chambers. This pushes the blood into the ventricles, theres a slight increase in ventricular pressure and chamber volume as the ventricles recieve the ejected blood from the contracting atria.

Question 2

Stage 2:

Answer 2

The atria relax and ventricles contract, decreasing their vol, increasing their pressure, pressure become higher in the ventricles than the artria = forcing the AV valves shut to prevent backflow. The pressure in the ventricles is also higher than in the aorta + pulmonary artery = forcing open the SL valves and blood is forced out into these arteries.

Question 3

Stage 3:

Answer 3

The ventricles and atria both relax, the higher pressure in the pulmonary artery and aorta closes the SL valves to prevent backflow into ventricles. Blood returns to the heart and the atria fill again due to higher pressure in the Vena Cava and pulmonary vein, in turn this starts to increase the pressure in the atria, as the ventricles continue to relax, there pressure falls below the pressure of the atria = AV valves open = blood flows passively into ventricles from the atria, atria contact + process starts again.