LECTURE #10

Muscles are the active part of the motor apparatus; their contraction produces various movements.

The muscles may be divided from a physiological standpoint into two classes: the voluntary muscles, which are under the control of the will, and the involuntary muscles, which are not.

All muscular tissues are controlled by the nervous system. The involuntary muscles are controlled by a specialized part of the nervous system.

When muscular tissue is examined under the microscope, it is seen to be made up of small, elongated threadlike cells, which arc called muscle fibers, and which are bound into bundles by connective tissue.

There are three varieties of muscle fibers:

1) striated muscle fibers, which occur in voluntary muscles;

2) unstriated muscles which bring about movements in the internal organs;

3) cardiac or heart fibres, which are striated like (1), but are otherwise different. Both unstriated and cardiac muscles are involuntary. All living cells can move to some degree, but this ability is highly developed in muscles. Muscle tissue comprises about 40% of human weight. Muscle consists of threads, or muscle fibers, supported by connective tissue, which act by fiber contraction: the fibers can shorten to two - thirds of their resting length. There are two types of muscles smooth and striated. Smooth, or "involuntary" muscles are found in the walls of all the hollow organs and tubes of the body, such as blood vessels and intestines. These react slowly to stimuli from the autonomic nervous system. The striated, or "voluntary" muscles of the body mostly attach to the bones and move the skeleton. Under the microscope, their fibers have a cross-striped appearance. Striated muscle is capable of fast contractions. The heart wall is made up of a special type of striated muscle fibers called cardiac muscle. Muscles vary greatly in structure and function in different organs and animals: some invertebrates have only smooth muscles, while all the arthropods have only striated muscles. The body is composed of about 600 skeletal muscles. In the adult about 35-40% of the body weight is formed by the muscles. According to the basic part of the skeleton all the muscles are divided into the muscles of the trunk, head and extremities.

According to the form all the muscles are traditionally divided into three basic groups: long, short and wide muscles. Long muscles compose the free parts of the extremities. The wide muscles form the walls of the body cavities. Some short muscles, of which stapedus is the smallest muscle in the human body, form facial musculature.

Some muscles are called according to the structure of their fibers, for example radiated muscles; others according to their uses, for example extensors or according to their directions, for example, - oblique. The muscles are formed by a mass of muscle cells. The muscle fibers are connected together by connective tissue. There are many blood vessels and nerves in the muscles.

Great research work was carried out by many scientists to determine the functions of the muscles. Three basic methods of study were used: experimental work on animals, the study of the muscles on a living human body and on the cadavers. Their work helped to establish that the muscles were the active agents of motion and contraction.

new words

muscles - muscles

active - active

part - part

motor apparatus - motor apparatus

various - various

movement - movement

elongated - elongated

threadlike - threadlike

to be bound - to be bound

some - some

degree - degree

this - this

ability - ability

capable - ability

scientist - scientist

basic - basic

experimental - experimental

work - work

Remember frozen phrases.

In the morning. In the evening to come home.

In the afternoon. At night to leave home for work (school).

To go to bed. to go to school at half past five.

To go to work, to go home at a quarter past five.

Insert the article where necessary.

1. My... friend has to get up early in... morning ing because he goes to... school.

2. That's why he usually goes to... bed early in... evening.

3... the weather was very bad in... morning yesterday.

4... the sky was gray and it was raining.

5. But in... middle of... day... the weather began to change.

6... rain stopped and... sun appeared from behind... clouds.

7. In... afternoon it was very warm.

8. I didn’t want to stay at... home and went into... yard.

9. There were... boys and... girls in... yard.

10. We played in... yard till late in... evening.

11. When I came... home, I drank... tea, ate... sandwich and went to... bed at once.

12. I slept very well at... night.

13. My brother is... pupil. He goes to... school. He goes to... school in... morning. He has five or six... lessons every day. In... afternoon he goes home. At... home he does his... homework.

14. In... evening he reads... books. He usually goes to... bed at... half past ten. At... night he sleeps.

15. My father goes to... work in... morning and comes... home in... evening.

16. I get up at... half past seven in... morning and go to... bed at... quarter to eleven in... evening.

17. When does your mother leave... home for... work?

18. She leaves... home for... work at... quarter past eight.

19. When do you leave... home for... school?

20. I leave... home for... school at... half past... eight.

Answer the questions.

1. What are the muscles?

2. What contraction produces various movements?

3. What may the muscles be divided from?

4. What does the nervous system control do?

5. What does the muscular tissue consist of?

6. How many varieties of muscle fibers are there?

7. How many per cents does muscle tissue contain?

8. For how many groups are all the muscles traditionally divided?

9. How sometimes are muscles called?

10. What does connective tissue connect?

Make the sentences of your own using the new words (10 sentences).

Find the definite and indefinite articles in the text.

Find one word, which is a little bit different in meaning from others (find one word that is slightly different from others in meaning):

1) a) work; b) job; c)rest;

2) a) class; b) student; c) sea;

3) a) home; b) house; c) garage

4) a) lift; b) down; c)rise;

5) a) white; b) pink c) scarlet.

Author: Elena Belikova

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