What is sleep ?

Sleep is a state which our body mind and conciseness falls into on a regular basis and in that state we are largely unaware of our surroundings.

Why do we sleep?

It is commonly believed that we sleep to rejuvenate the mind and body although the actual reasons why we sleep have never been been accurately isolated we know that it we do not sleep we start to suffer from fatigue of both body and mind.

If we do not sleep we start to feel tired and with that comes a slow down of many of our mental and physical activities.

So we can best figure out why we sleep by locking at the effects of not sleeping, but that does not answer the basic question. It has been found that the body uses only a little less energy while sleeping than it does while awake. So although we it makes sense on the face of it......the idea that we sleep to rest the body does not actually hold true under sleep study.

But sleep studies concerning mental activity and functioning can be mapped fairly accurately. The brain and the mind are severely effects by lack of sleep and go into a decline very quickly. And the only remedy for that decline.......is sleep.

Types of sleep

There are essentially two types of sleep.

Non REM Sleep
REM Sleep

REM Sleep.

REM stands for Rapid Eye Movement and

REM sleep starts to happen about an hour and a half after we fall asleep. Sleep study has shown that brain wave activity in REM sleep is similar to that while we are awake.

We also dream during REM sleep whearas in Non REM sleep it is thought that we do not dream.

The percentage of REM sleep declines as we get older. Small children spend up to half of their sleep in the REM stage of sleep, whereas adults spend only about 20% in REM.

Non REM Sleep.

Sleep studies have also shown that Non REM Sleep can be split up into 4 distinct stages

Stage 1: The eyes are closed during Stage 1 sleep. But it is easily interrupted and if you are woken up you might not think that you have been asleep. A feeling of falling sometimes happens in this stage of Non REM Sleep and can jolt you back to being awake.
Stage 2: In this second stage the body starts to relax more deeply and the heart rate will usually decrease.
Stage 3: Stage three is the first onset of deep sleep, the muscles of the body are very relaxed. This stage is also known as slow-wave sleep because studies show that the brain activity is at its least.
Stage 4: This is the final sage of deep sleep before REM sleep.

How much sleep do we need.

The amount of sleep we need depends upon a few things. One of the main difference seems to be age.

As a rule of thumb:

Babies sleep for about 17 hours each day.
Older children only need 9 or 10 hours a night.
Most adults need around 7-8 hours sleep each night.
Older people need the same amount of sleep, but will often only have one period of deep sleep during the night, usually in the first 3 or 4 hours, after which they wake more easily. We also tend to dream less as we get older.

This seems to be very much a standard with children but as we get older our individual sleep patterns change. Some people regularly get 4 - 6 hours of sleep per day and do very well on that but others require more 7 - 8 hours seem to be the average.