Biological rhythms

• What are circadian rhythms?

  Patterns of behaviour occurring every 24 hours
• What sets circadian rhythms?

  Environmental light levels
• What is the master circadian pacemaker in humans?

  Suprachiasmatic nuclei (SCN)
• Where are the suprachiasmatic nuclei located?

  In the hypothalamus
• What are ultradian rhythms?

  Cycles lasting less than 24 hours
• What are infradian rhythms?

  Cycles lasting more than 24 hours
• How long can infradian rhythms last?

  Days, weeks, months, or years
• Give an example of a Circadian rhythm

  Sleep-wake cycle
• Give an example of an Ultradian rhythms

  Sleep stages
• Give an example of an infradian rhythms

  Menstrual cycle
• What was the procedure in Michael Siffres study?

  Spent 6 months in a cave with no natural light
• What was the result of Michael Siffres study regarding his internal body clock?

  Settled in a sleep/wake cycle of 25 hours
• What does the result of Michael Siffres study suggest about the natural sleep-wake cycle?

  It may be longer than 24 hours
• What maintains the natural sleep-wake cycle according to the study?

  Exogenous zeitgebers such as light
• What was the procedure in Dement and Kisteinan's study?

  Monitored sleep of a fish in a lab using EEG
• What did Dement and Kisteinan find regarding sleep stages?

  Sleep occurred in stages, with REM being complex
• What does the result of Dement and Kisteinan's study support?

  The idea of distinct stages in sleep
• What was the procedure in Stern and McClintock's study?

  Pheromones from 29 women were gathered
• How were the pheromones collected in the study?

  Using cotton pads in the armpit
• What was the result regarding menstrual synchrony in the study?

  68% of women experienced changes in their cycles
• What does the result of Stern and McClintock's study support?

  The evolutionary idea of synchronized pregnancies