Final answer:
The typical NREM-REM sequence lasts approximately 90 minutes.
Step-by-step explanation:
The typical NREM-REM sequence lasts approximately 90 minutes.
Sleep is divided into two general phases: REM sleep and non-REM (NREM) sleep. NREM sleep is further divided into three stages. The typical NREM-REM sequence starts with NREM stage 1, followed by NREM stage 2, NREM stage 3 (also known as deep sleep or slow-wave sleep), and ends with REM sleep. This sequence repeats throughout the night, with each cycle lasting approximately 90 minutes.