Sleep · Sleep
Sleep Stages & Circadian Rhythm
Sleep is a cycle of light, deep and REM stages, about 90 minutes long, timed by two systems: sleep pressure (adenosine) and the circadian clock (light, melatonin). What each stage does and how caffeine, light and alcohol interfere.
Step 1 of 5 · Overview30 min read ·
Key idea
Prereqs: How neurons work (helpful). Next: Sleep & memory. Sources: Borbély's two-process model (1982); AASM/NSF sleep guidelines; Matthew Walker's *Why We Sleep* (some claims contested); Khan Academy MCAT.Not medical advice. Education only; check with a doctor before major changes, especially with a medical condition.
Next: 1. The stages