Further ejection and relaxation cause ventricular pressure to fall. When ventricular pressure falls below aortic pressure, the aortic valve closes and isovolumetric relaxation ensues. When ventricular pressure falls below atrial pressure the mitral valve opens and the filling phase begins. Tension increases at constant radius causing increased pressure. Radius decreases at constant tension causing further increase in pressure 4.
Tension decreases at constant radius causing decreased pressure.