When the heart contracts the body tissue receives its blood supply. When the heart relaxes the heart ventricles receive its blood supply.
Explanation:
The cardiac cycle consists of contraction and relaxation of the heart. The contraction is called systolic pressure and relaxation is called diastolic pressure.
The systole and diastole are mainly concerned with the ventricles, still, articular contraction and relaxation also occur. The blood from the auricles pushes into the ventricles. This is because of the auricular contraction. This initiates by SA node with a "Lub" sound.
The contraction means the pressure of the blood is more in the auricle and the mitral valve and tricuspid valves open. The blood enters the ventricles. Then the pressure of auricles becomes less.
Now the ventricles are filled with blood and the pressure of the blood is more in the ventricles. This is called ventricular systole, and it leads to open the semilunar valves.
The blood is ejected out by aorta and supply to different parts of the body. After the blood ejection, the ventricles are in the relax stage, which is called the diastolic stage.
One systolic pressure is followed by one diastolic phase. Due to systolic pressure/ contraction, the blood pumps out of the heart.
