circadian rhythms

• Circadian rhythm

  Rhythms that last for around 24 hours

  e.g. Sleep/wake cycle
• Sleep/wake cycle

  • governed by internal pacemaker
  • suprachiasmatic nucleus (SCN)
• Suprachiasmatic nucleus

  provides information from the eye about light
• Siffre's cave study

  • Spent extended periods underground to study the effects on his biological rhythms
  • Deprived of natural light/sound
  • Resurfaced after 2 months believing it was August when it was September.
  • 'free-running' biological rhythm was 25 hours
• Aschoff + Wever's study (WW2 bunker)

  • Participants spent 4 weeks in a WW2 bunker.
  • All but 1 participant had a circadian rhythm between 24-25 hours.
  • Suggests entrained by natural light ot make shorter than it is.
• Strength -> practical application

  • shift work
  • accidents and mistakes common during 'circadian trough' (6am)
  • health consequence for shift workers
• Limitation -> individual differences

  • free running sleep/wake cycle can range from 13-65 hours
  • may change with age
  • siffre's later cave study had slower circadian rhythmn