6. WORK OF THE HUMAN HEART
The human heart contracts from the first moment of life until the last one. The contractions of the heart pump the blood through the arteries to all the parts of the body. Physiologists have determined that in the adult the heart makes from 60 to 72 beats per minute. In children the rate of heart beat is much higher. Research work has determined that rate of heart beat increases depending on different emotions.
Each beat of the heart is followed by a period of rest. Each contraction and a period of rest compose a cardiac cycle.
Each cardiac cycle consists of three phases: the first phase of short contraction — the atrial systole, the second phase of a more prolonged contraction — the ventricular systole. The period of rest is called the diastole.
Research work of many physiologists has estimated the role of the ventricles as the main pump of the human heart.

Упражнение. Переведите следующие предложения:
1. The human heart makes 60—80 contractions per minute.
2. On physical exertion the heart has a short period of rest and the diastole becomes less.
3. Ten tons of blood are pumped through the heart daily.
4. The heart acts as a pump.
5. John Floyer, an English doctor, was the first scientist 1 to find out the varying pulse rate in men.

Упражнение. Найдите в тексте эквиваленты следующих русских слов и выражений:
человеческое сердце, сокращаться, сокращения сердца, артерия, взрослый человек, 72 удара в минуту, определить частоту сердцебиения, зависит от различных эмоций, сердечный цикл, систола предсердия, систола желудочка, диастола, насос.