circadian rhythms

• biological rhythms


  • distinct changes in body activity that conform to cyclical time periods
  • influenced by internal body clocks + changes in environment
• circadian rhythms 


  • type of biological rhythm
  • 24-hour-cycle
  • regulates a number of body process
• sleep/wake cycle 


  • drowsy when its night time, alert during the day= effect of daylight
  • if light didn't exist- would we know if it was night + day and when to go to sleep
• siffre's cave study 


  • spent several periods underground to study effects on biological rhythms
  • deprived of natural light + sound (still had food + drink)
  • came out in September + thought it was August
  • did it again for 6 months- biological rhythms of 25 hours
• circadian rhythms- other research 


  • Aschoff and Wever
  • pps spent 4 weeks in WW2 bunker- deprived of natural light
  • other pps- sleep/ wake cycle- 29 hours
  • suggests that natural cycle may be slightly longer than 24 hours
• circadian rhythms- evaluation


  strength: practical application to shift work

  • mistakes made when rhythm desynchronised + poor health
  • economic implications on research

  strength: practical application

  • pharmaceutics applies understanding of circadian rhythms to improve drug effectiveness

  weakness: use of case studies + small samples

  • lack of generalisability e.g., Siffre was over 60 and small samples