Stage 1. Drowsiness
This is the short transitional stage between being awake and falling asleep. During this stage, your muscles start relaxing, your breathing and heartbeat slow down and you’re getting ready for sleep. Muscle contractions and slow eye movements are typical for this stage.
Stage 2. Light Sleep
As was the case with the previous stage, during light sleep you’re still partly awake and quite easy to wake. Your body further relaxes and your brain waves slow down and eye movements typically stop. This stage can last 20 minutes or more, with research showing that this is the stage we spend the most time while we sleep.
Stages 3 and 4. Moderate and Deep Sleep
During these stages, people experience the deepest sleep, which is characterized by the slowest heart rate, brain waves, and breathing. During this crucial stage, a person fully relaxes and it’s very difficult to wake them up. Deep sleep is essential for the formation of new memories and the excretion of important hormones in the brain. This is the stage that allows your brain to relax and replenish itself after a long day of thinking and collecting information.
Stage 5. REM Sleep
The final stage of the sleep cycle is the so-called REM sleep, named after the characteristic rapid eye movements observed during this stage. During this stage, brain activity increases to its wakeful norm and we start dreaming. Simultaneously, our bodies become temporarily paralyzed to prevent us from acting out whatever we’re doing in our dreams.