Ultradian rhythms

• Ultradian rhythm


  A biological rhythm that takes less than 24 hours to complete one cycle
• Stages of sleep


  1. N1 (non-REM)

  2. N2 (non-REM)

  3. N3 (non-REM)

  4. REM (Rapid eye movement)
• One cycle of the stages of sleep takes about 90 minutes and repeats 4-5 times over the course of a night's sleep
• Each cycle tends to include a larger proportion of REM sleep and shorter duration of N3
• EEG (Electroencephalogram)


  Measures distinctive brain wave patterns to identify sleep stages
• Brain waves measured by EEG

  • Delta
  • Theta
  • Alpha
  • Beta
  • Gamma
• Theta and Delta brain waves

  Distinguish sleep stages
• N1 (falling asleep)


  • Easy to wake up
  • Sudden body movements (hypnic jerks)
  • Sensation of falling
  • Hypnagogic hallucinations
• N2 (sleep)


  • Harder to wake
  • Body is relaxed
  • Heart rate and body temperature are lowered
  • Eyes are still
• N3 (deep sleep)


  • Very difficult to wake
  • Body is most relaxed
  • Heart rate is lowest
  • Brain wave frequency slows and amplitude increases
• REM sleep


  • Similar to wakefulness on EEG
  • Body is paralysed
  • Rapid eye movement
  • Associated with dreaming
• After REM sleep


  The brain returns to N1
• Strength - Shaprio: Ultrmarathon runners hoed longer sleep after intense physical activity. Also, an increased proportion of slow wave sleep (N3)

  • Supports the theory SWS is for the body’s physical recovery.
• Strength Haider: EEGs of 10 patients recovering from drug overdose showed increased REM sleep.

  • Suggesting REM is for mental recovery.

   
• Weakness - The overall pattern of sleep stages is consistent, however, there are individual differences, with newborn babies spending 80% of sleep in REM compared to 20-25% in adults.

  • Suggests the stages of sleep is not a simple process but adapts to the developmental needs of the individual.