VI. Answer the questions

What does the PNS consist of?

What system controls involuntary functions in the body?

What do these functions include?

What functions does the sympathetic system control?

What functions does the parasympathetic system control?

VII. Translate from Russian into English

Нервная система – это сеть биллионов взаимосвязанных нервных клеток (нейтронов), которые получают стимулы, координируют сенсорную информацию и заставляют тело отвечать соответствующим образом.

Нервная система состоит из двух главных отделов: центральной нервной системы, которая состоит из головного и спинного мозга, и периферической, которая состоит из спинномозговых и черепных нервов.

Рецепторы – это различные чувствительные клетки и органы, чья функция – воспринимать и передавать стимуляцию.

ЦНС интегрирует информацию из ПНС и посылает инструкции к различным частям тела.

Головной мозг также участвует в процессах мышления, обучения, памяти и связан с интеллектом.

Рецепторы ПНС сигнализируют в ЦНС об изменениях в окружающей среде.

Автономная нервная система – часть нервной системы, которая контролирует непроизвольные функции, такие как биение сердца, движение кишечника и потоотделение.

АНС состоит из двух отделов: симпатической и парасимпатической нервной системы.

Симпатическая нервная система контролирует функции, которые готовят организм для немедленной деятельности.

Симпатическая нервная система повышает кровяное давление и пульс, увеличивает продукцию глюкозы печенью, уменьшает секрецию слюны, вызывает поднятие волос кожи, расширяет зрачки.

Парасимпатическая нервная система уменьшает кровяное давление и сердцебиение, сужает зрачки, увеличивает секрецию слюны и повышает активность желудка и кишечника.

CARDIOVASCULAR SYSTEM

Part I: Composition of blood

Cardiovascular system, comprising both the heart and the blood vessels, circulates blood throughout the body. It carries essential supplies of food and fuel to every living cell and exchanges them for potentially harmful waste products. The adult circulation consists of thousands of miles of tubing containing about 10 pints (4.7 l) of blood. The blood is kept flowing round the body by the pumping action of the heart.

Blood is made up of a pale yellow liquid (plasma) containing dissolves nutrients and wastes, plus blood cells, hormones, proteins and other substances. Most numerous of these cells are the disk – shaped red blood cells. Their color comes from the presence of the substance hemoglobin, which combines with oxygen. When red corpuscles charged with oxygen approach body cells, the oxygen is delivered in exchange for the waste product carbon dioxide. Other two – way transportation of materials takes place between the body cells and the plasma, and all unwanted substances are carried away by the kidneys, lungs and liver. Plasma also contains white blood cells, which help to fight infection, and platelets, which are involves in blood clotting.

Part II: Arteries and veins

In its passage through the body, blood is carried in tubes known as arteries and veins. Most arteries transport oxygen-rich (oxygenated) blood, whereas most veins transport carbon dioxide-rich (deoxygenated) blood. The largest artery is the aorta, which stems directly from the heart. The aorta and other large arteries have thick walls lined with muscle. Blood flow is assisted by the contraction of this muscle and the impetus given from the heartbeat. The “push” from the heart can be felt as the pulse wherever large arteries run near the body surface.

As they penetrate the tissue, arteries split into narrow branches called arterioles, which in turn divide into capillaries. It is through the very thin capillary walls that the blood gives up its oxygen and nutrients and receives carbon dioxide and wastes. Deoxygenated blood in the capillaries flows into narrow veins (venules), and then into veins. The two largest veins, the venae cavae, return this blood to the heart. Veins have thin walls compared with those of arteries, and blood moves through the veins much more slowly. Blood flow in the veins is assisted by the action of muscles in surrounding tissues, and the backflow is prevented by one-way valves.

The deoxygenated blood delivered to the heart along the veins is no use to body cells until it has been recharged with oxygen. To ensure reoxygenation, the circulation has a second “loop”. In this part of the system, blood rich in carbon dioxide travels from the heart along the pulmonary artery to the lungs, where carbon dioxide is exchanged for oxygen breathed in. the pulmonary artery is the only artery to carry deoxygenated blood. The newly oxygenated blood is carried back to the heart along the pulmonary vein, the only vein to transport oxygenated blood.

Part III: The structure and the action of the heart

The heart is a muscular organ about the size of a clenched fist. The structure and action of the heart are designed to serve the two loops of the circulation. Inside, the heart is divided vertically by a muscular wall. On each side of this wall is an upper chamber (atrium) and a thicker, lower chamber (ventricle). Blood moves through each side of the heart systematically. Deoxygenated blood is delivered into the right atrium. It then enters the right ventricle, from where it is pumped out into the pulmonary artery and to the lungs. Oxygenated blood returning in the pulmonary veins flows into the left atrium. This blood enters the left ventricle and is then pumped into the aorta for circulation.

The flow of blood in each side of the heart is controlled by a series of valves. The pumping action of the heart is achieved by the contraction of the cardiac muscle, of which the heart is largely composed. The rhythm of the heartbeat is regulated by bursts of electrical impulses sent out by a concentration of specialized heart tissue called the pacemaker.

Under the influence of the pacemaker, the heart of an adult at rest beats at a rate of 60 to 80 beats a minute. The pacemaker also helps to ensure the correct sequence of activities during each heartbeat; first the two atria contract, followed rapidly by the ventricles. The powerful contraction of the ventricles pushes blood into the aorta and pulmonary artery. This period of contraction (systole) is followed by a period of relaxation (diastole), during which the heart refills. The complete sequence is accompanied by electrical activity of the muscle, which can be monitored as an electrocardiogram (EKG).

Part I: Composition of blood

I. Practice the pronunciation and stress

hemoglobin	[ˏhi:mə`gləubın]
hormone	[`hɔ:məun]
oxygen	[`ɔksıʤən]
carbon dioxide	[`ka:bən daı`ɔksaıd]
protein	[`prəuti:n]
to transport	[træns`pɔ:t]