Cardiac cycle: The cardiac cycle describes all the activities of the heart through one complete heartbeat—that is, through one contraction and relaxation of both the atria and ventricles.
Cardiac systole: The systole is the part of the cardiac cycle during which some chambers of the heart muscle contract after refilling with blood.
Atrial systole: The contraction of the atria by which blood is forced into the ventricles; it precedes the true or ventricular systole and is indicated by the fourth heart sound.
Ventricular systole: The contraction of the ventricles, forcing blood into the aorta and pulmonary artery.
Systole: The contraction, or period of contraction, of the heart, especially of the ventricles, during which blood is forced into the aorta and pulmonary artery
Diastole: The phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood.
I hope this helps :)
