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.
The semilunar valves are the aortic valve and the pulmonic valve, which allow the blood to flow from the left ventricle to the aorta and from the right ventricle to the pulmonary artery.he semilunar valves are the aortic valve and the pulmonic valve, which allow the blood to flow from the left ventricle to the aorta and from the right ventricle to the pulmonary artery.