What Is Sleep

What Is Sleep?
Sleep is the regular period in every 24 hours when we are unconscious and unaware of our surroundings. There are two main types of sleep:

Rapid Eye Movement (REM) sleep

It comes and goes throughout the night, and makes up about one fifth of our sleep time. During REM sleep, our brain is very active, our muscles are very relaxed, our eyes move quickly from side to side and we dream.

Non-REM sleep
The brain is quiet, but the body may move around. Hormones are released into the bloodstream and our body repairs itself after the wear and tear of the day.

There are 4 stages of non-REM sleep:

   1. The muscles relax, the heart beats slower and body temperature falls - "pre-sleep".
   2. Light sleep - we can still be woken easily without feeling confused.
   3. "Slow wave" sleep - our blood pressure falls, we may talk in our sleep or sleep walk.
   4. Deep "slow wave" sleep - we become very hard to wake. If we are woken, we feel confused.

We move between REM and non-REM sleep about five times throughout the night, dreaming more as we get toward the morning.

During a normal night, we will also have short periods of waking. These last 1 or 2 minutes and happen every 2 hours or so. We aren't usually aware of them. We are more likely to remember them if we feel anxious or there is something else going on - noises outside, our partner snoring etc.