Circadian rhythms

• Biological rhythms: Distinct patterns of changes in the body activity that conform to cyclical time periods. These are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers).
• Circadian rhythms: Biological rhythms, subject to 24 hour cycles, these regulate a number of body processes such as the sleep/wake cycle and changes in body temp.
• All biological rhythms are governed by two things: Endogenous pacemakers (Internal) and exogenous zeitgebers (external).
• The sleep/wake cycle key influences:

  • Daylight is an important exogenous zeitgeber.
  • The SCN (suprachiasmatic nucleus) is also an important endogenous pacemaker which acts as an internal body clock, it provides info about light to the eye.
• Siffre’s cave study:

  • Spent several months underground to see how the lack of light affected his sleep/wake cycle.
  • His biological rhythm turned into around 25 hours, his schedule remained regular.
  • However he believed that when he resurfaced in September that it was only August.
• Aschoff and Wever (1976):

  • Put participants into a bunker deprived of natural light.
  • All but one (whose sleep/wake cycle extended to 29 hours) displayed a circadian rhythm between 24-25 hours.
• Research shows that maybe biological clock is a tiny bit longer than 24 hours but daylight (an exogenous zeitgeber) makes it shorter.
• Folkard eat al:

  • Put 12 people into a cave with clocks.
  • They slowly changed the time to a 22 hour day and only 1 participant comfably adjusted.
  • Shows how we may be overestimating exogenous zeitgebers
• Circadian rhythms- Evaluation (strength)

  • Provides understanding of adverse consequences of shift work.
  • night workers are more likely to have poorer health and concentration.
  • This shows how research into the sleep/wake cycle may have real-world economic implications.
• Circadian rhythms- Evaluation (limitation)

  • Counterpoint of shift work.
  • Difficult to establish if there is other factors that affect shift workers concentration e.g higher divorce rate,
  • Correlation doesn’t equal causation.
• Circadian rhythms- evaluation (strength)

  • It has been used to improve medical treatment.
  • For example it has helped show that aspirin is most affective at night.
  • This shows how circadian rhythm research can help effectiveness of drug treatments.
• Circadian rhythms- Evaluation (limitation)

  • Generalisations are difficult to make.
  • Studies used small sample sizes, cycles differ depending on the person.
  • Difficult to use research data on anyone who hasn‘t been involved themselfs.