There are four stages in the sleep cycle, with a fifth stage of REM (Rapid Eye Movement) Sleep. Here are some things you need to know about these stages.
Stage 1: This stage is an early stage of sleep. You are not fully in deep sleep yet, your muscles are starting to relax and your eyes are moving slowly. It may be easier to wake up during this stage. You are essentially half asleep and half awake.
Stage 2:Stage 2 is where your heart rate and breathing begins to slow down. Body temperature slightly decreases and eye movement stops.
Stage 3: Deep sleep begins in this stage. Slow Delta waves are being generated in the brain. It may be hard to wake you up. After you wake up from stage 3, you may feel groggy and it may be difficult to adjust right away.
Stage 4: This stage is a continuation of deep sleep, but more intense. Blood is flowed away from the brain and its primary focused is restoring energy for the muscles. Brain waves are going to be slow. Just like stage 3, it may be hard to wake up in this stage.
REM (Rapid Eye Movement) Sleep: REM Sleep typically occurs 90 minutes after falling asleep. This stage you may experience dreaming and increased brain activity while your eyes are moving back and fourth. Blood pressure and heart rate increases while your body is paralyzed.
Sources:
https://sleephealth.org/sleep-health/importance-of-sleep-understanding-sleep-stages/
