Michael Warren, age 8, of Guntersville, Ala., for his question:
WHAT HAPPENS DURING SLEEP?
All human beings and almost all kinds of animals must have a certain minimum amount of daily sleep at regular intervals. Sleep is a period of rest when the sleeper actually loses awareness of his surroundings, much as one would in a coma. With sleep, however, a person can easily be awakened with a gentle nudge, the sound of an alarm or the flash of a bright light.
Most adults, sleep between seven and nine hours a night, with eight being about average. Some get by with as little as six hours while other people seem to need more than nine.
When you fall asleep, all of your activity decreases and the muscles of your body relax. Your heartbeat and breathing rate slow down. Slowly you become unaware of what is happening around you.
The position of your entire body will change at least a dozen times during about eight hours of sleep. Your head, arms and legs will move more often.
An electroencephalograph is an instrument scientists have used to study sleep and to find out exactly what happens in your body during slumber. The electroencephalograph measures and records brain waves both when a person is awake and when he is asleep.
A relaxed person getting ready for sleep will give off about 10 small brain waves each second. As he falls into sleep, the brain sends out slower but larger and larger waves. The slowest, largest waves take place during the first two or three hours of sleep.
During periods of time when the testing equipment will show slow wave sleep, mental activity slows down but does not stop. Persons awakened from slow wave sleep can quite often recall an unclear thought that they had while asleep.
Periods of small, fast waves, much like those of an awake person, also happen at intervals during sleep. During these periods of fast brain wave activity the sleeper's eyes move rapidly as though they were watching the events of a dream. If a sleeper is awakened during such a period, he probably will recall that he had been dreaming and remember details of the dream. Sleep during these periods is called dreaming sleep or REM, meaning rapid eye movement sleep.
Sleep restores energy to the body, particularly the brain and nervous system. People need both the slow wave sleep and dreaming sleep. Extra sleep of either kind does not make up for a lack of the other. Slow wave sleep may help especially to restore the control of the brain and nervous system over the muscles, glands and other body systems. Dreaming sleep may be especially important for maintaining such mental activities as learning, reasoning and emotional adjustment.