heart

Question 1

atrial systole

Answer 1

the ventricles relaxes, the atria contract, decreasing the volume of the chambers and increasing the pressure inside the chambers. this pushes the blood into the ventricles. there’s a slight increase in ventricular pressure and chamber volume as the ventricles receive the ejected blood from the contracting atria

Question 2

ventricular systole

Answer 2

the atria relaxes and the ventricles contract, increasing their pressure. the pressure becomes higher in the ventricles than the atria, which forces the AV valves shut to prevent backflow. the pressure in the ventricles is also higher than in the aorta and pulmonary artery, which forces open the SL valves and blood is forces out into the arteries.

Question 3

diastole

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 the ventricles. blood returns to the heart and the atria fill again due to the higher pressure in the vena cava and pulmonary vein. this increases the pressure of the atria. as the ventricles continue to relax, their pressure falls below the pressure of the atria and so the AV valves open.