Describe the cardiac cycle (sis , diarrhea) (4)

A heart beat is made up of contraction (systole) and relaxation (diastole) contraction = increases P in atria and ventricles = blood flows from area of high pressure to low pressure Systole: when ventricles contract, AV valves close to stop backflow into atria = blood into arteries (1st sound) bicuspid and tricuspid valves close Diastole: when ventricles relax, semilunar valves close = stops backflow into ventricles = blood into arteries (2nd sound) blood flows out of the heart through the arteries (pulmonary and aortic arteries)