The sleep cycle is a set of phases that begin from the moment the person falls asleep and progresses and becomes deeper and deeper until the body goes into REM sleep.
Normally, REM sleep is the most difficult to achieve, but it is at this stage that the body can actually relax and in which the rate of brain renocation is greater. Most people follow the following pattern of sleep phases:
- Phase 1 light sleep;
- Phase 2 light sleep;
- Phase 3 deep sleep;
- Phase 2 light sleep;
- Phase 1 light sleep;
- REM sleep.
After being in the REM phase, the body returns to phase 1 and repeats all phases until it returns to the REM phase again. This cycle repeats itself throughout the night, but the time in REM sleep increases with each cycle.
Get to know the 8 major disorders that can affect the sleep cycle.
How long does the sleep cycle last?
The body goes through several cycles of sleep during one night, the first lasts about 90 minutes and then the duration increases, up to an average of 100 minutes per cycle.
An adult usually in between 4 to 5 sleep cycles per night, which ends up doing the necessary 8 hours of sleep.
The 4 phases of sleep
Sleep can then be divided into 4 phases:
1. Light sleep (Phase 1)
This is a rather light sleep phase that lasts about 10 minutes. Stage 1 of sleep begins when you close your eyes and the body begins to fall asleep, however, it is still possible to wake easily with any sound that happens in the room, for example.
Some features of this phase include:
- Do not realize that you are already asleep;
- Breathing slows down;
- You may have the feeling that you are falling.
During this phase, the muscles are still not relaxed and so the person still moves in bed and can even open their eyes while trying to fall asleep.
2. Light sleep (Phase 2)
Phase 2 is the stage that almost everyone refers to when they say they are light-hearted. It is a phase in which the body is already relaxed and sleeping, but the mind is attentive and therefore the person can still wake easily with someone moving inside the room or with a noise in the house.
This phase lasts for about 20 minutes and in many people is the stage at which the body spends more time throughout all sleep cycles.
3. Deep sleep (Phase 3)
This is the phase of deep sleep in which the muscles completely relax the body becomes less sensitive to external stimuli such as movements or noises. At this stage the mind is disconnected and therefore there are no dreams either. However, this stage is very important for body repair as the body will trying to recover from minor injuries that have been arising during the day.
4. REM Sleep (Phase 4)
REM sleep is the last stage of the sleep cycle, which lasts for about 10 minutes and usually starts 90 minutes after falling asleep. At this stage, the eyes move very fast, the heart rate increases and dreams appear.
It is also at this stage that a sleep disorder known as sleepwalking can arise, in which the person can even get up and walk around the house without ever waking up. The REM phase will be more time consuming with each sleep cycle, and can reach up to 20 or 30 minutes in duration.
Learn more about sleepwalking and 5 other strange things that can happen during sleep.
