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.
Chapter 12. Cardiac cycle . 1. During which phase of the cardiac cycle are the atrioventricular, aortic semilunar and pulmonary semilunar valves all open? a. ventricular filling phase b. isovolumetric ventricular relaxation phase c. ventricular ejection phase d. these valves are never all open at the same time . 2.