The rate of heart contractions is regulated by two groups of nerve fibers. It varies in different persons and at different age. 





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The rate of heart contractions is regulated by two groups of nerve fibers. It varies in different persons and at different age.



Physiologists have determined that in the adult the heart makes from 60 to 72 beats per minute. In children the rate of heartbeat is much higher. Research work of many scientists has helped to determine that the rate of heartbeat increases 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.

Research work has given physiologists the possibility to find out that the heart muscle works or contracts about one third of the time of the person’s life. The period of rest is shorter during greater physical exertion and longer when the body is at rest.

Each cardiac cycle consists of three phases: physiologists have called the first phase of short contraction of both atria - the atrial systole. They have called the second phase of a more prolonged contraction of both ventricles - the ventricular systole. The period of rest of the cardiac muscle is calledthe diastole.

The left ventricle discharges out the blood received by the left atrium from the pulmonary circulation through the aorta to the systemic circulation.

The blood received from the systemic circulation by the right atrium is discharged out of the right ventricle to the lungs through the pulmonary arteries.

Prolonged research work of many physiologists has given the possibility to estimate the role of the ventricles which serve as the main pump. The atria act as receiving chambers. The contraction of the atria which sends the final portion of the blood into the ventricle is considerably less.

CLASS ASSIGNMENTS

XIII. Read the following words and explain the pronunciation of the letters and letter combinations in bold type:

Quality, quantity, coat, throat, quick, question, dead, treat, mouth, month, cause, cover, quinsy, qualified.

XIV. Form the adjectives using the suffix -able. Translate them:

Consider, change, depend, vary, eat, question, work.

XV. Name and translate the verbs from which the following nouns are formed:

Operation, circulation, estimation, radiation, location, separation, graduation, dilatation, regulation.

XVI. Supply ‘already’ or ‘yet’. Translate the following sentences:

The scientists have introduced this term. 2. The researchers have not found out the origin of this disease. 3. The physiologists have estimated the importance of this great discovery. 4. They have not published the book on their discoveries.

XVII. Translate the following sentences:

The human heart begins to beat and pump blood quicker than usual during the emotional stress. 2. The human heart makes 60-80 contractions per minute. 3. On physical exertion the heart has a short period of rest and the diastole becomes less. 4. The heart acts as a pump discharging out the blood to peripheral and pulmonary systems. 5. Ten tons of blood are pumped through the heart daily. 6. John Floyer, an English doctor (1649-1734), was the first scientist to find out the varying pulse rate in men.

XVIII. Put the verbs in the required form. Translate the following sentences:

The nurse already (to take temperature). 2. The doctor not yet (to use) this method of treatment. 3. She not (to see) her parents since May. 4. The nurse just (to determine) the patient’s blood group.

XIX. Choose the proper answer from those given below:

1. Did the scientists find out the total weight of the blood? (a) The scientists find out the total weight of the blood; (b) The scientists found out the total weight of the blood; (c) The total weight of the blood was found out by the scientists. 2. Is the rate of the heartbeat regulated by two groups of nerve fibers? (a) The rate of the heartbeat will be regulated by two groups of nerve fibers; (b) Two groups of nerve fibers have regulated the rate of the heartbeat; (c) The rate of the heartbeat is regulated by two groups of nerve fibers.

XX. Translate the following sentences paying attention to the words in bold type:

Я часто посылаю письма своим родителям. 2. Я только что послал письмо своим родителям. 3. Вчера я послал письмо своим родителям. 4. Вчера я послал письмо своим родителям до того, как пошел на лекцию. 5. Какие фотографии вы посылаете сейчас своим родителям? 6. Я пошлю письмо своим родителям в следующий понедельник. 7. Я пошлю письмо своим родителям к концу этой недели.

XXI. Translate into English:





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