Cardiac output is the volume of blood pumped by one ventricle of the heart in one minute.

cardiac output = heart rate × stroke volume

Diastole is the phase of the cardiac cycle where the heart relaxes.

Blood flows into the atria through the pulmonary vein and the vena cava, pushing open the atrioventricular valves and filling the ventricles.

During atrial systole, the atrial walls contract, forcing the remaining blood into the ventricles.

Throughout this stage, the muscle of the ventricle walls remains relaxed.

During ventricular systole, the ventricle walls contract simultaneously, increasing blood pressure within them.

This closes the atrioventricular valves and forces blood into the aorta and pulmonary artery.

Valves in the heart ensure blood flows in one direction.

Valves open when pressure differences favour movement in the required direction and close when pressure differences would cause blood to flow in the opposite direction.