Final answer:
During a typical night's sleep, a person cycles through the four sleep stages multiple times. The four stages are NREM sleep (stage 1, stage 2, and stage 3) and REM sleep. Each cycle lasts about 90-110 minutes.
Step-by-step explanation:
During a typical night's sleep, a person cycles through the four sleep stages multiple times. The four stages of sleep are called NREM (non-REM) sleep and REM (rapid eye movement) sleep. NREM sleep is divided into three stages: stage 1, stage 2, and stage 3. Stage 1 is a transitional phase between wakefulness and sleep, lasting about 5-10 minutes. Stage 2 is a light sleep stage, characterized by sleep spindles and K-complexes, and it takes up about 45-55% of a sleep cycle. Stage 3 is considered deep sleep or slow-wave sleep, with predominance of delta waves. REM sleep is the dreaming stage, where brain waves are similar to wakefulness and rapid eye movements occur. The entire sleep cycle, from stage 1 to REM sleep, takes about 90-110 minutes to complete. This cycle is repeated multiple times throughout the night, with progressively shorter periods of NREM sleep and longer periods of REM sleep as the night goes on.