Select the correct answers to the questions from the given options. (Do not copy the questions, write the correct answer only.)
During the ventricular systole, the atrioventricular valves (P) __________ and the semilunar valves (Q) __________.
Topic: Cardiac cycle — valve action
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Answer
(a) P - close and Q - open.
SYSTOLE means contraction. When the ventricles contract, the pressure inside them rises sharply, and that single fact decides both valves: the ATRIOVENTRICULAR valves (tricuspid and bicuspid) are pushed SHUT, preventing blood flowing back into the atria — this shutting produces the first heart sound, "lubb" the SEMILUNAR valves (at the openings of the aorta and pulmonary artery) are forced OPEN, letting blood out into the arteries
THE PRINCIPLE to carry away: blood moves from high pressure to low, and valves simply open in the direction of flow and close against it. Work out where the pressure is highest and the valve positions follow.
During ventricular DIASTOLE the reverse happens — semilunar valves close (the "dupp" sound) and the atrioventricular valves open.
P - close and Q - open.