By the time we reach old age most of us have spent twenty years sleeping . Yet nobody knows why we do it. Most scientists believe that by resting our bodies, we allow time for maintenance work to be done . Any damage that there is can be put right more quickly if energy isn’t being used up doing other things.
Sleep is controlled by certain chemicals. These build up during the day, eventually reaching peaks that cause tiredness. We can control the effects of these chemicals to some extent. Caffeine helps to keep us awake while alcohol and some medicines make us sleepy.
By using electrodes, scientists are able to study what goes on in people’s heads while they sleep.They have discovered that when we first drop off everything slows down. The heart beats more slowly, and our breathing becomes shadow. After about ninety minutes our eyes start to twitch, and we go into what is called REM sleep, which is a signal that we’ve started to dream. You have dreams every night, even if you don’t remember them. There are many theories about why we dream, none of them conclusive. A lot of people say they have to have eight hour’s sleep every night while others seem to manage on a lot less. One thing is certain-we all need some sleep. Going without it can have some very strange effects