How many of us know what our body goes through during this seemingly simple period of inactivity?

Up to the 1950's sleep was regarded as a time when a persons body and mind shut down for the night.
3: Very slow brain activity, frequent small brain activity bursts. Moving through all the stages from 1 to REM is known to be in one single sleep cycle. As the length of time we have been asleep each night increases so does our time during each sleep cycle that we remain in REM, the deep sleep stages of 3 and 4 reducing. Neurotransmitters like norepinephrin and serotonin, released from the brain stem between the lower brain and top of the spinal column, act to make certain sections of our head fully functional whilst we are awake. Difficult to disturb at this deep sleep level. Long-term memory is reorganized, tissue is renewed or repaired, the mind is rejuvenated. Muscles in limbs become paralyzed temporarily.

Whilst asleep it is believed that important restorative and adaptive bodily functions are in progress. When we begin to go to sleep there are other neurons at the base of our brains that become active, switching off the activity of the neurons that keep us awake. Half of our sleep involves stage 2, 20% involves REM, the other stages taking up the remaining 30% of our sleeping time. Sensations of falling are not uncommon in this stage.

When asleep people typically pass through five sleep stages:

1: Light sleep where we can be easily disturbed.Many of us really enjoy falling into bed and drifting off to sleep, particularly after a hard days work. Younger people tend to have a greater degree of deep sleep than the older population.
2: Eye movements stop, brain activity slows, infrequent rapid bursts of brain activity exist. Through neurological and hormonal processes light appears to trigger people to remain awake, although light is not always required to achieve this result, e.g. usually at night and around mid-afternoon. Eye and muscle movements are slow. What we now know is that various parts of our brain are in fact very active throughout the time we spend asleep. with night shift workers inverting their days work and sleep periods. Dreaming is frequent and sometimes vivid. Once asleep adenosine is known to be broken down. Slowly, we are unraveling these secrets to what exactly goes on.e.

Our brains contain very high quantities of nerves, better known as neurons, to which signaling chemicals termed neurotransmitters act to enable us to be asleep or awake. 6-8 hours of sleep per day is all that the average person requires.</p>
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To a certain extent whilst in REM our bodies are unable to regulate their temperatures, unusually hot or cold temperatures can disturb this sleep stage. Losses in REM time tend to involve the next sleep cycles REM being longer so as to regain what REM time was previously lost. If awoken, takes a few minutes to orientate one's self. Time spent asleep is important with preparing us for the challenges of the next day.
4: Only slow brain activity occurs now. LED Light Housing Increased time spent awake leads to a build-up of time that person needs sleeping. Throughout the day a chemical known as adenosine is believed to accumulate, it has the effect of making people more and more tired.

Our bodies have a biological 24-hour time clock known as a circadian rhythm, with peaks of sleepiness occurring every 12 hours i.

These sleep stages make up a sleep cycle that is completed roughly every 90-110 minutes. Hear beats increase per minute alongside increased blood pressure.
REM (rapid eye movement): Increased breathing, more irregular, shallow breathing, rapid random eye movement. No eye or muscle activity. Difficult to disturb at this deep sleep level.