the stage of the heart beat when the heart is relaxed is called
The first stage,  diastole , is when the semilunar valves (the pulmonary valve and the aortic valve) close, the atrioventricular (AV) valves (the mitral valve and the tricuspid valve) open, and the whole heart is relaxed.uring the fifth stage,  isovolumic relaxation time , pressure decreases, no blood enters the ventricles, the ventricles stop contracting and begin to relax, and the semilunar valves close due to the pressure of blood in the aorta. Throughout the cardiac cycle, blood pressure increases and decreases.