Stage 1 is light sleep where you drift in and out of sleep and can be awakened easily.In this stage, the eyes move slowly and muscle activity slows.A complete sleep cycle takes an average of 90 to 110 minutes, with each stage lasting between 5 to 15 minutes.The first sleep cycles each night have relatively short REM sleeps and long periods of deep sleep but later in the night, REM periods lengthen and deep sleep time decreases.As the night progresses, individuals spend increasingly more time in REM sleep and correspondingly less time in deep sleep. Typically, an individual will go through four to five sleep cycles a night.Stages 3 and 4 are referred to as deep sleep, slow wave sleep, or delta sleep. Children are nearly impossible to wake up from this stage, and may be prone to bedwetting, sleepwalking or night terrors.The different cycles of sleep last for different amounts of time during the night.Non-REM sleep dominates the first half of the night, while the amount of time spent in REM stage sleep increases during the second half.
“It’s nice to wake up in the morning with someone next to you. Infants spend almost 50% of their time in REM sleep.Adults spend nearly half of sleep time in stage 2, about 20% in REM and the other 30% is divided between the other three stages.These behaviors are known as During REM (rapid eye movement) sleep, brain waves mimic activity during the waking state.The eyes remain closed but move rapidly from side-to-side, perhaps related to the intense dream and brain activity that occurs during this stage.Since then, scientists have also disproved the idea that deprivation of REM sleep can lead to insanity and have found that lack of REM sleep can alleviate clinical depression although they do not know why.Recent theories link REM sleep to learning and memory.Rather, a sleep cycle progress through the stages of non-REM sleep from light to deep sleep, then reverse back from deep sleep to light sleep, ending with time in REM sleep before starting over in light sleep again.For example, the order looks something like this: After REM sleep, the individual returns to stage 1 of light sleep and begins a new cycle. After that, they average between 100 to 120 minutes.During deep sleep, human growth hormone is released and restores your body and muscles from the stresses of the day. Much less is known about deep sleep than REM sleep.It may be during this stage that the brain also refreshes itself for Slow wave sleep comes mostly in the first half of the night, REM in the second half.