HOW THE NERVOUS SYSTEM AND MUSCLES WORK

Did you know your child was lucky enough to own his own computer? What is more, he can also operate it! How’s that for competence, without any formal training, and without having to purchase anything?

In fact, his computer was given to him by you at birth. What is more, it will last him for the rest of his life, and it will keep working, year in and year out, until he dies from old age. It is the human brain. This wondrous bit of machinery, plus the electrical hook-up that goes with it, forms the nervous and muscular system of the body.

The computer is carefully locked up in a strong-room; its walls are made of solid bone, which is almost as strong as concrete. This is aimed at protecting it from injury throughout life.

From the lower back part, a thick tail extends downwards, through a canal formed by adjoining holes in the bones that make up the backbone, or spinal column. This thick, rope-like structure is called the spinal cord. As it descends down the back, it becomes gradually thinner. At regular intervals, where the vertebral bones join each other, a nerve is given off from the main cord. This tracks out and divides into many smaller divisions. Each goes to a certain part of the body or to a group of muscles.

In the head region, these are called the cranial nerves. At the level of the arms, large ones are given off and these supply the upper limbs. Lower down, huge nerves branch off to form the giant sciatic nerve which supplies the lower limbs.

All activities must start somewhere, and the beginning is the brain. Here, ideas are quickly translated into messages that are instantly conveyed to the appropriate part of the brain. Electrical impulses are then sent to the muscles concerned; the muscles contract and movement takes place. All this can happen with the speed of lightning.

The body is very fussy that the brain system be kept clean and free from germs or injury. For this reason it is covered with a thin sheet of tissue called the meninges—an important protective layer. Also, the brain is bathed in fluid called cerebro-spinal fluid. This helps protect it from sudden jarring movements which could otherwise damage it.

The entire spinal cord is made up of microscopic strands which commence in the brain and end in various muscles and organs of the body. (It is very similar to telephone cables which carry thousands of individual wires that extend from the exchange to a person’s telephone in the home. Each is capable of carrying an enormous number of messages, and the exchange knows exactly where the individual messages are headed for.)

The telephone system

But just as things can go wrong with the telephone system, so disorders may occur in the nerves. The brain itself may become diseased, as germs penetrate the coverings and produce brain damage that may be serious or even life-threatening. Also, the insulating material of the nerves may become impaired or diseased, causing short-circuits. This is represented by certain so-called demyelinating disorders.

Sometimes the brain is damaged before birth, and severe defects may occur, such as spina bifida or hydrocephalus. The electrical system of the brain may be defective, causing epilepsy. These disorders may occur before birth. Some develop afterwards, and indeed some may take place at any time during life.

Nerves frequently extend to muscles. Each muscle is made up of millions of tiny individual fibres, and each has a nerve attached to it. If an electrical impulse reaches the muscle, it causes it to contract or shorten. When thousands of these act together, it makes the entire muscle shorten, and in this way movement is possible. By shortening the muscles of the arm, for example, we can bend the arm, the hand, or the fingers. Impulses from the brain can be sent to other groups of muscles in the body at the same time. This is how we are capable of moving about and performing normal activities.

But just as the nerves can be diseased for various reasons, so the muscle fibres may suffer from various defects. Fortunately they are not very common in infancy and childhood.

Some nervous system disorders are common in infancy, but most are fairly uncommon. Convulsions during a fever are frequent, and epilepsy is also fairly common. Developmental anomalies are rarely seen by family doctors.

We will discuss some of the more probable disorders so that you may recognise them. At all times, any suspected abnormality of the brain or nervous system should prompt quick medical attention from the doctor. Today, many serious disorders may be successfully treated. The sooner this commences, the better.

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