When sleeping, people go through four non-REM-sleep stages {sleep cycle}, separated by short REM-sleep periods. Sleep cycles last 90 minutes and have short dreaming stage 1, then stage 2, then stage 3, then stage 4, then stage 3, then stage 2, then dreaming stage 1, and then waking. In stage 1, heart rate and respiration rate increase, and brain is active [Dement, 1972]. Sleep gets deeper through the night. Deep sleep is greatest at 2 AM.
Consciousness>Consciousness>States>Sleep>Sleep Cycle
1-Consciousness-States-Sleep-Sleep Cycle
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Date Modified: 2022.0224