Diastole is the part of the cardiac cycle when the heart refills with blood following systole (contraction). Ventricular diastole is the period during which the ventricles are filling and relaxing, while atrial diastole is the period during which the atria are relaxing. The term diastole originates from the Greek word διαστολη, meaning dilation. Diastole is closely related to the phenomenon of recoil within ballistics.