Opteonâ¢ YF (HFO-1234yf) is a low global warming potential (GWP) refrigerant for use in automotive air-conditioning systems. Opteonâ¢ YF (HFO-1234yf) has a chemical structure of CF3CF= CH2 2,3,3,3-tetrafluoropropene.
During isovolumetric relaxation, which is the second last phase of the cardiac cycle, all the heart valves are closed. This means that there is no blood passing between the cardiac chambers or out of the heart. The pressure drop below 120 mmHg as the ventricles relax causes the semilunar valves to close. As the pressure drops further, the atrial pressure exceeds that of the ventricles and the atrioventricular valves open. Meanwhile, blood is being pumped around the body.
1. semilunar valve-a heart valve with cusps shaped like half-moons; prevents blood from flowing back into the heart. aortic valve-a semilunar valve between the left ventricle and the aorta; prevents blood from flowing from the aorta back into the heart.pulmonary valve-a semilunar valve between the right ventricle and the pulmonary artery; prevents blood from flowing from the artery back into the heart.. semilunar valve-a heart valve with cusps shaped like half-moons; prevents blood from flowing back into the heart. aortic valve-a semilunar valve between the left ventricle and the aorta; prevents blood from flowing from the aorta back into the heart.