The stages and cycle of sleep. PSYA3. AQA.

The stages and cycles of sleep as according to the AQA specification for PSYA3.

Taken from my 2013 notes.

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Stage 1

  • Lasts approximately 15 mintues.
  • The EEG levels are characterised by theta waves.
  • EOG indicates rolling eye movements.
  • EMG shows reductions in muscle tension.
  • Heart rate and temperature fall.
  • A hypnogogic state may occur, causing hallucinations e.g myclonic jerks.
  • The lightest stage of sleep and we are easily awakened.
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Stage 2

  • Lasts approximately 20 minutes.
  • EEG activity is characterised by larger and slower theta waves and short bursts of high frequency sleep spindles.
  • EOG shows little eye movement.
  • EMG shows the muscles are relaxed.
  • K-complexes also occur; our response to external and internal stimuli.
  • It is still easy to be awakened.
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Stage 3

  • Lasts approximately 15 minutes.
  • EEG activity is characterised by long, slow delta waves with some sleep spindles.
  • The EOG and EMG are the same as stage 2.
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Stage 4

  • Lasts approximately 30 minutes.
  • Also known as slow wave sleep (SWS) because of the long, slow delta waves of the EEG.
  • This is deep sleep so it is hard to wake someone from.
  • Body temperature, heart rate and blood pressure drops to their lowest point.
  • Growth hormones are secreted.
  • The stage when parasomnias, such as sleep-walking and night terrors occur.
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Stage 5 (REM)

  • Lasts approximately 10 minutes in the 1st cycle and builds up to an hour by the 4th and 5th cycles.
  • EEG activity is characterised by beta waves, which also occur during a relaxed waking state.
  • This high level of brain activity is linked to dreaming.
  • Also been called paradoxical sleep because of the EEG readings show that the brain is very active, whilst the EMG readings show that the body is paralysed.
  • It is the hardest sleep to wake someone from, as the paralysis prevents us from acting out our dreams.
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