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* The ventricles relax
* The pressure inside the ventricles drops below that in the arteries
* Blood under high pressure in the arteries causes the semi-lunar valves to shut . preventing blood from going back into the ventricles . This produces the second part of the heart sound " dub "
* During diastole all the muscle in the heart relaxes
* Blood from the vena cava and pulmonary veins enters the atria .The whole cycle stars again