PAIN AND THE NERVOUS SYSTEM
Pain involves the entire central nervous system — the brain, spinal cord, all the nerve fibres and billions of nerve cells. The central nervous system controls the voluntary muscles; that is, the ones you consciously control and which involve such everyday actions as walking, combing your hair or bending over to pick up things.
Pain also involves one component of the autonomic (automatic) nervous system called the sympathetic system. This controls the involuntary muscles of the body — the ones that function automatically — including the heart muscles, which control the pumping of the blood around the body, and the arteries, which have muscles in their walls allowing them to open and close. Other examples are the muscles that control the iris of the eyes and the muscles that control breathing. The sympathetic nerves also control the small arteries that control the flow of blood to the muscles.
The nerves are the most important piece of the pain puzzle. Their endings pick up pain signals which are started by a stimulus such as a pinprick. These nerve endings are found in all body tissues except the hair and nails. The nerves transmit the pain message, or signal, to its final destination — like a conveyor belt, taking messages to the brain and away from it. Tens of thousands of different nerves exist in the human body and there are about ten billion nerve cells in the brain. The nerve fibres vary in thickness and length. The nerves are either thick or thin. The thick ones have a coating of fatty material — the myelin, which acts like an electrical conductor to carry messages, or signals, along the nerves.
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