Psychology / Unit 4: States of Consciousness
4.2 Stages of Sleep
Notes
A full sleep cycle lasts about 90 minutes, and people go through four to six cycles per night.
- NREM stage 1: light sleep, drifting off; sometimes a feeling of falling.
- NREM stage 2: sleep spindles (bursts of activity); body temperature drops.
- NREM stage 3: deep, slow-wave sleep. Hard to wake; important for physical restoration and memory.
- REM sleep: rapid eye movements, vivid dreams, high brain activity, and muscles are temporarily paralyzed. Important for learning and emotion.
- Early in the night there is more deep sleep; REM periods get longer toward morning.
- Brain waves: awake and alert (beta), relaxed (alpha), deep sleep (delta).
Practice
In which stage of sleep do vivid dreams, rapid eye movements and temporary muscle paralysis occur?
REM is linked to vivid dreaming; muscles are paralyzed to prevent acting out dreams.
Which brain waves are mainly seen in deep sleep?
Slow delta waves are the signature of stage 3.
Over the course of a night of sleep, REM periods generally:
Deep sleep dominates early; REM lengthens later in the night.
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