Stages of Sleep
There are four stages of non-REM sleep.
Stage I Sleep
- Slowing of the pulse
- Muscle relaxation
- Side-to-side rolling movements of eyes
- Low voltage brain waves produced during relaxed wakefulness or the twilight stage between waking and sleeping are called alpha waves. These brain waves then change to theta waves.
- Images sometimes appear but not true dreams.
- Sleeper is easily awakened during Stage 1.
Stage II Sleep
- Starts about 5 to 7 minutes after entering Stage I.
- Does not respond to noise or light.
- Heart rate, blood pressure and temperature continue to drop.
- slower more regular wave patterns.
- Theta waves show short periods of extremely fast and higher energy wave activity called sleep spindles.
Stage III Sleep
- Brain waves become slower with higher peaks and lower valleys. This stage starts with theta waves with some higher energy delta waves.
Stage IV Sleep
- Occurs during the early part of the night.
- Very slow delta waves.
- Sleep spindles disappear.
- Heart and breathing rates, blood pressure and body temperatures are as low as they will get during the night.
