Ultradian Rhythms/ Nature of Sleep/ Sleep Stages

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  • Created by: rhallett
  • Created on: 10-11-15 18:13
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  • Ultradian Rhythms/ Nature of Sleep/ Sleep Stages
    • There are 5 different stages of sleep which are defined by brain waves using an EEG
    • As a person goes through non-REM, stages 1-4, their brain waves become larger in voltage and slower/more spread out
    • Stage 1) Brain produces Theta waves (5-7 Hz), easy to wake up, person is only slightly asleep
    • Stage 2) Still Theta waves, K Complexes occur, large and spiky waves possibly linked to sudden noises. Bursts of faster activity known as sleep spindles also occur
    • Stage 3) Large, slow Delta wave (0.5-2 Hz) now occur and the person is deeply asleep, hard to wake
    • Stage 4) Delta waves now dominate the EEG
    • REM Sleep
      • After 90 mins of NREM sleep, REM sleep begins:
        • Stage 1) The EEG resembles the waking Stage 1 state and the brain appears active. Brain waves are fast, desynced and low in voltage
        • Stage 2) The person's eyes move rapidly but all other muscles are paralysed
        • Stage 3) Complex dreams occur
    • Sleep stages are an ultradian rhythm because one cycle of REM/NREM takes 90 mins; less than 24 hrs.
      • In a night's sleep the person will go through 4-6 Stages of NREM and REM sleep
        • Deepest sleep (Stages 3 and 4) happens during the first part of the night, while periods of REM get longer towards morning


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