The two processes in the cardiac cycle: systole an
The cardiac cycle is the complete sequence of events during one heartbeat.
When the heart contracts, the heart chambers are called systole and pump the blood.
When the heart relaxes, the heart chambers are called diastole, and blood flows back into the heart.
The walls of the heart are made of of cardiac muscle, which does not tire. The walls of the left ventricle of the heart are thicker because they have to pump blood around the whole body while the right ventricle only has to pump blood to the lungs.