What are the main stages of sleep, including REM and non-REM sleep?

Sleep is a fundamental biological process that allows the body and brain to rest, repair, and consolidate memories. There are two main types of sleep: rapid eye movement (REM) sleep and non-rapid eye movement (non-REM) sleep. Both types of sleep are necessary for good health and well-being.

Non-REM sleep is divided into three stages: Stage 1, Stage 2, and Stage 3. Stage 1 is the transition from wakefulness to sleep and is characterized by light sleep, where brain waves begin to slow down. During Stage 2, brain waves continue to slow down, and the body begins to relax further. Stage 3 is the deepest stage of sleep, also known as slow-wave sleep, where the brain waves are slow and regular.

REM sleep is the stage of sleep where the brain is most active and dreaming occurs. It is called REM sleep because of the rapid eye movements that occur during this stage. REM sleep is important for memory consolidation and emotional regulation. During REM sleep, the body is in a state of paralysis to prevent acting out dreams.

Each sleep cycle typically lasts around 90 minutes and includes both REM and non-REM sleep. The amount of time spent in each stage of sleep varies throughout the night, with more time spent in deep sleep early in the night and more time spent in REM sleep in the later hours.