circadian rhythms

• what are the 2 things that govern biological rhythms?

  • endogenous pacemakers
  • exogenous zeitgebers
• what are cycles that take more than 24-hours called?

  infradian rhythms
• what are cycles that take 24-hours called?

  circadian rhythms
• what are cycles that take way more than 24-hours called?

  circannual rhythms
• give 2 examples of circadian rhythms

  • sleep wake cycle
  • core body temperature
• what is the sleep wake cycle?

  the cycle of being awake and being asleep
• give an example of exogenous zeitgebers

  light
• give an example of endogenous pacemakers

  suprachiasmatic nucleus
• which study tested the effect of exogenous zeitgebers?

  siffre's cave study
• what did siffre do?

  • stayed in a cave for a period of time
  • deprived of exposure to natural light and sound, but had access to adequate food and drink
  • resurfaced in mid september 1962 but believed it was mid august
  • 10 years later he peformed a similar study but this time for 6 months
  • in this study, his sleep wake cycle was just beyond the usual 24 hours though he did continue to wake up and fall asleep on a regular schedule
• what does siffre's study suggest?

  • the natural sleep wake cycle may be slightly longer than 24 hours but that it is entrained by exogenous zeitgebers associated with our 24 hour day (eg, mealtimes)
• give 1 strength of research into circadian rhythms

  • provides an understanding of the adverse consequences that occur when they are disrupted (desynchronisation)
  • eg, study by boivin, night shift workers often have a period of reduced concentration around 6:00 in the morning meaning mistakes were more common etc
• give 1 strength of research into circadian rhythms

  • been used to improve medical treatments
  • eg, aspirin, used as a treatment to reduce heart attacks, has been proven as best used late at night in order to correspond with someones biological rhythm
  • heart attacks are more likely to happen in the early morning so this suggests that circadian rhythm research can help increase the effectiveness of drug treatments
• give 1 limitation of research into circadian rhythms

  • generalisations are hard to make
  • the study by siffre involved only one participant, this is not representative and most studies only involve a few participants
  • it seems that the sleep wake cycle may vary person to person. research by duffy et al revealed some people just prefer going to sleep earlier / when its lighter, whereas some people prefer the opposite
  • this suggests that its difficult to use the research data to discuess anything more than averages which may be meaningless