What Happens When You Sleep – 4 Stages

We all have heard that people need to get 8 hours of sleep a night because it is important and good for their health. Have you ever wondered about what all is going on while you are sleeping?

Firstly, sleep is comprised of 4 stages. Stage 1-3 is non-REM sleep, and Stage 4 is REM sleep. People cycle through Stages 2-4 several times a night.

Stage 1 is when people are just drifting off, and the body’s physiology starts to slow down (brain activity, breathing, heart rate, blood pressure, body temperature). Some people’s muscles can also randomly jerk as they are falling asleep. During this stage, people can easily be woken up because it has the lightest sleep. Stage 1 lasts less than 10 minutes.

Stage 2 is light sleep, in which the body’s activities slow down even more. However, certain parts of the brain become slightly more active, allowing more resistance to being woken up and helping people to stay asleep. Stage 2 lasts about 25 minutes.

Stage 3 is deep sleep, in which the body’s functions slow down the most. It is also the hardest to wake people up at this stage. If woken up, they need several minutes to become fully oriented. During deep sleep is when healing occurs, repairing body tissues and strengthening the immune system. Stage 3 lasts between 20-40 minutes initially and gets shorter with each sleep cycle as the night goes on.

Stage 4 is REM sleep (rapid eye movement). During this time, all the body’s activities that slowed down during Stages 1-3 start going back up. In fact, the brain activity during REM sleep is almost as high as when people are awake. During this time is when memory and learning are consolidated. People may also dream during REM sleep. Stage 4 lasts 10 minutes initially and gets longer with each sleep cycle, lasting up to an hour closer to morning.

Because of all the vital activities that occur during sleep, it is very important for people to have good quality sleep and also sleep enough hours that is ideal for them.

As an original pioneer of sleep medicine, said: “If sleep doesn’t serve an absolutely vital function, it is the biggest mistake evolution ever made”.

Written by Anna Diec, LAc

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