The Work of the Human Heart The human heart contracts from the first moment of life to the last one. The contractions of the heart pump blood through the arteries to all the parts of the body Scientists have determined that the total weight of the blood pumped by the hemi daily is about 10 tons. Physiologists have established that in the adult the heart makes from 60 to 7,' beats per minute.4n children the rate of heartbeat is much higher. Research work of many scientists has helped to determine that the rate of heartbeat increase depending on different emotions. Each beat of the heart is followed by a period of rest for the cardiac muscle Each wave of contraction and a period of rest following it compose a cardiac cycle The period of rest is shorter during greater physical exertion and longer when the body is at rest. The physiologists called the first phase of short contraction of both atria - the atrial systole, the second phase of more prolonged contraction of both ventricles- the ventricular systole. The period of rest of the cardiac muscle is called the diastole The blood received by the left atrium from the pulmonary circulation is discharged out by the left ventricle to the systemic circulation through the aorta. The atria act as receiving chambers.