Sleep can be categorized into four primary stages:
1. NREM Stage 1: This is the lightest stage of sleep, where the transition from wakefulness to sleep occurs. It typically lasts a few minutes. 2. NREM Stage 2: This stage is characterized by a decrease in body temperature and heart rate. Sleep spindles and K-complexes, which are types of brain activity, can be observed. 3. NREM Stage 3: Known as deep sleep or slow-wave sleep, this stage is crucial for physical restoration. The body repairs tissues, builds bone and muscle, and strengthens the immune system. 4. REM Sleep: Occurring about 90 minutes after falling asleep, REM sleep is when the brain is most active, and dreams occur. This stage is essential for cognitive functions like learning and memory.
