What is sleep?

We all recognize what sleep actually is and know when we've experienced it,
but behind the scenes a complex process is taking place.





There are five stages of sleep, which recur in 90 minute cycles.
When you get six to eight hours sleep a night, it allows at least four phases of repairing and rebuilding to take place.

When we first drift off, we enter the first stage between sleeping and being awake. Muscle activity slows down but occasional twitches and movement are not uncommon. We can be woken up easily.

Phase two normally follows within 10 minutes of the first period of light sleep. Our heart rate and breathing slow down. while our body temperature drops. Muscle movement is less likely and we remain in this state for upto 20 minutes - the greater proportion of the cycle.

We experience deep sleep during stage three. when out heart rate and breathing slow down even further and become rhythmic. Finally in stage four we experience the deepest level of sleep. Brain and muscle activity are minimal.

A period of Rapid eye movement (REM) sleep follows, so called because our eyes dart about beneath closed eyelids. Our brain becomes more active and our breathing becomes more rapid and shallow. The muscles remain relaxed, although are leg and facial muscles can twitch.

This is the time during our sleep when we dream, and if woken at this stage we are more likely to remember what we have dreamet. After a period of REM sleep, we return to stage one and the cycle begins again. We can experience upto five periods of REM a night which explains why we can sometimes wake up and remember a series of dreams.

It is normal for us to move about and change positions during our sleep.
This is the body's way of making sure that the circulation is not cut off in an area for too long.