Don Raines, aged 12, of Atlanta, Ga,., for his question:
What causes sleep?
Night is the time for sleep. We get into comfortable clothes, open the window and turn out the light. We curl up in a soft warm bed and close our eyes. These preparations help the body to put itself to sleep. Then comes the mystery _ the mystery of sleep. It steals over us and we know no more until morning. Maybe we remember a dream. But it soon goes when we feel the freshness of a bright near day.
Sleep is something of a mystery even to the experts. They know what happens to the sleeping body. They know it gets needed rest and wakes up refreshed. But they are not certain what causes it or how it begins. However, the experts have some theories about the cause of sleep. A theory is a maybe ‑ a good idea. without enough facts to prove it.
The whole body is rested and refreshed by sleep. This includes the wonderful nervous system. All day long this works like a busy telephone system. It brings messages to the brain from the eyes, ears, nose, taste and touch. It works out problems and flashes orders all over the body. It works through central switchboards, some in the brain and some in the spinal column.
One theory says that maybe part of the nervous system gets tired after a days work. So it simply closes down certain of its switchboards, It stops most of the incoming calls from the senses. It refuses to solve any more problems. However, it leaves a few alarm bells in case of emergencies. Aloud noise, a bright light, hunger or cold, can alert the sleeping nervous system. These things will wake us from sleep. That is why we make preparations to avoid them at bed time.
The nervous system seems to have a built‑in switch for putting itself to sleep. This switch goes on by itself when we are tired and properly prepared for bed. Certain blood vessels tighten up and shut off the blood supply to the brain. This is a way of forcing it to rests For it needs food and energy to think and work. And its food and energy comes from the comes from the blood supply.
There are certain machines for testing the activity of the brain. One measures the waves, or electric impulses, given off by a busy brain. This machine shows that brain waves change during sleep. During waking hours, a switchboard area in the back of the brain is very alert and active. When sleep comes, the activity dies down in this area of the brain.
Other switchboards of the nervous system stay in operation. They are the areas that control the breathing and the heart beat. During bleep they simply slow down a little. The body may lose some of its warmth, that is why we prepare for bed with warm blankets.
All through sleep, the body is resting end rebuilding itself. The nervous system may also be getting rid of waste materials. During the day it may be too busy to do this. Ideas and impressions rush in from all directions. It has to work to cope with them all. One theory says that the nervous system must sleep to get rid of the waste materials that collect during the day. At any rate, by morning the good old nervous system is all ready to go with a new day full of sights, sounds, smells, ideas and problems.