Non-REM Phase
Sleep begins with Non-REM stages, progressing from light to deep sleep. Stage 1 marks the transition from wakefulness, lasting several minutes with slowing brain waves. Stage 2 features sleep spindles and K-complexes in brain activity, while Stages 3 and 4 represent deep sleep with slow delta waves. During these stages, the body repairs tissues, builds bone and muscle, and strengthens the immune system.
REM Sleep
Rapid Eye Movement (REM) sleep occurs approximately 90 minutes after falling asleep. During REM, brain activity increases to levels similar to wakefulness, while the body experiences temporary muscle paralysis. This stage hosts vivid dreams, processes emotional information, and consolidates memories. Adults typically experience 4-6 REM cycles per night, with longer periods toward morning.
Cycle Regulation
Sleep cycles repeat throughout the night, with each cycle lasting about 90-120 minutes. The circadian rhythm, controlled by the hypothalamus, regulates this pattern using light exposure and hormone production, particularly melatonin. Environmental factors, stress, and age affect cycle quality and duration, influencing overall sleep architecture and restoration.Shutdown123