Most scientists think we sleep becauseKip, nap ,doze ,forty winks ,shut-eye and snooze are all expressions we use to describe that mysterious state, sleep. We all do it ,we can’t get by without it and by the time we reach old age most of us have spent 20 years sleeping .Yet ,nobody knows why we do it. Most scientists reckon that by resting our bodies, we allow time for essential 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 . Injured animals certainly spend more time asleep than usual while their wounds are healing. And quite a few illnesses make us feel drowsy so our body can get on with curing us. Sleep is controlled by certain chemicals .These build up during the day , eventually reaching levels that make us tired. 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 shallow. After about 90 minutes our eyes start to twitch and we go into what is called REM sleep. REM stands for Rapid Eye Movement ,and it’s a sign that we’ve started to dream . You have dreams every night ,even if you don’t remember them.There are all sorts of theories about why we dream .One is that it gives the brain a chance to sort out the day’s activities , filling everything away in the right place. Another is that the brain gets bored while we’re asleep and organizes its own entertainment - a sort of late - night cinema ! A lot of people say they have to have eight hours ‘ sleep every night while others seem to manage on a lot less . One thing’s for sure , we all need some sleep and going without it can have some very strange effects .An American disc-jockey ,who stayed awake for 200 hours to raise money for charity ,thought things were bursting into flames all around him after 120 hours without sleep .He survived the ordeal but was depressed for three months afterwards. |