circadian rhythms

• the nature of circadian rhythms

  • circadian rhythms last 24hr
  • master circadian pacemaker is SCN
  • SCN is reset daily by light
  • sleep-wake cycle is on a circadian cycle
  • sleep and wakefulness also under homeostatic control
  • case-study- Micheal Siffe
  • core body, temp varies with a circadian rhythms
  • hormone production follows circadian cycle
• evaluation/discussion


  • importance of light-tested in Antarctic (Hughes)
  • individual differences- cycle length varies between 13 and 65 hours (Czeilser et al)
  • research methology- early studies did not isolate participants from artificial light
  • chronotherapeutic- developments of 'circadian cycle friendly' medications
  • temperature more important than light in setting circadian rhythms (Buhr et al)