KINE 1P90 Lecture Notes - Lecture 9: Heart Valve, Heart Sounds, Diastole
17 Feb 2017
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One cycle of contraction and one relaxation of the myocardium (heart) One complete sequence of contraction and relaxation of the heart. During contraction, the whole muscle squeezes in to the center, the sarcomere shortens towards the centre, which changes the pressure in the chambers. During the cardiac cycle, the pressure within the chambers rises and falls. When the atria are relaxed, blood flows into and through them. When the atria contact (atrial systole), the pressure in the atria rises forcing blood into the ventricles. This is followed by the atria relaxing (atrial diastole) As the ventricles contract (ventricular systole), the bicuspid and tricuspid valves close, and blood flows out of the ventricles into the arteries. When the ventricles relax (ventricular diastole), the bicuspid and tricuspid valves open and blood flows from the atrium into the ventricle. To open, we need pressure higher in the atria. To close, we need pressure higher in the ventricles.
