Circadian Rhythms

• What are biological rhythms?

  Distinct patterns of changes in body activity
• What influences biological rhythms?

  Endogenous pacemakers and exogenous zeitgebers
• What are endogenous pacemakers?

  Internal body clocks regulating biological rhythms
• What are exogenous zeitgebers?

  External factors affecting biological rhythms
• How often do some biological rhythms occur?

  Many times during the day or longer
• What are circadian rhythms?

  Biological rhythms with a 24-hour cycle
• What are ultradian rhythms?

  Biological rhythms with more than one cycle in 24 hours
• What are infradian rhythms?

  Biological rhythms with less than one cycle in 24 hours
• What was the aim of Siffre's 1972 study?

  To discover effects of no exogenous zeitgebers
• What was Siffre's procedure in his study?

  Cave explorer deprived of light and sound
• What did Siffre have access to during his study?

  Food and drink
• What did Siffre keep during his study?

  A diary of sleep and wake patterns
• What were Siffre's findings regarding his sleep patterns?

  Initial patterns were erratic, then regular
• What was Siffre's natural circadian rhythm duration?

  25 hours
• How long did Siffre spend in the cave?

  2 months
• How did Siffre perceive the duration of his stay in the cave?

  He believed it to be only 1.5 months
• How has research into circadian rhythms been applied in medical treatment?

  Improved effectiveness of drug treatments
• What is chronotherapeutics?

  Field improving drug treatment effectiveness
• What consequence do night workers face due to circadian rhythm disruption?

  Reduced concentration around 6 a.m.
• What real-world implications does research into the sleep/wake cycle have?

  Managing worker productivity effectively
• What methods do studies on shift work typically use?

  Correlational methods
• What did Solomon (1993) conclude about shift workers?

  High divorce rates linked to deprived sleep
• What limitation exists in research on circadian rhythms?

  Difficult to generalize findings
• What did Aschoff & Wever (1976) and Siffre (1972) studies reveal?

  Based on small samples of participants
• What did Czeisler et al (1999) find about sleep/wake cycles?

  Individual differences vary from 13 to 65 hours
• What does the variability in sleep/wake cycles imply for research data?

  Data may only discuss averages meaningfully
• What is a strength for Circadian Rhythms?

  • Medical Treatment
  • Research into circadian rhythms has been used to improve medical treatments
  • Circadian rhythms coordinate a number of the body’s basic processes, which rise and fall during the course of a day, which led to the field of chronotherapeutics
  • This shows that circadian rhythm research can help increase the effectiveness of drug treatments
• What is a strength for Circadian Rhythms?

  • Shift Work
  • Research into circadian rhythms provides an understanding of the consequences that occur when they are disrupted
  • For example, night workers engaged in shift work experience a period of reduced concentration around 6.a.m, meaning mistakes and accidents are more likely
  • This shows that research into the sleep/wake cycler may have real-world economic implications in terms of how best to manage worker productivity
• What is a limitation for Circadian Rhythms?

  • Correlational Methods
  • Studies investigating the effects of shift work tend to use correlational methods
  • Soloman (1993) concluded that high divorce rates in shift workers might be due to the strain of deprived sleep and other influences, such as missing out on important family events
  • This suggest that it may not be biological factors that create the adverse consequences associated with shift work
• What is a limitation for Circadian Rhythms?

  • Individual Differences
  • Generalisations are difficult to make with research into circadian rhythms
  • Studies such as Aschoff & Wever (1976) and Siffre (1972) are based on very small samples of participants, and sleep/wake cycles vary widely from person to person, as Czeisler et al (1999) found individual differences in sleep/wake cycles varying from 13 - 65 hours
  • This means that it is difficult to use the research data to discuss anything more than averages, which may be meaningless