Circadian rhythms

• What are circadian rhythms subject to?

  A 24-hour cycle
• What are circadian rhythms?

  Biological rhythms that regulate body processes such as sleep/wake cycle and changes in core body temperature
• What are the two examples of circadian rhythms?

  Sleep/wake cycle and core body temperature
• What is an exogenous zeitgeber on our sleep/wake cycle?

  Daylight
• What is an endogenous pacemaker on our sleep/wake cycle?

  Suprachiasmatic nucleus
• What is the biological clock known as?

  Suprachiasmatic nucleus
• What is the suprachiasmatic nucleus?

  Provides information from the eye about light
• What can reset the suprachiasmatic nucleus?

  Light
• Who studied the effects of several extended periods underground on biological rhythms?

  Siffre
• What did Siffre find in his studies into the effects of several extended periods underground on biological rhythms?

  His 'free-running' biological rhythm settled down to one that was beyond the usual 24-hours but continued to fall asleep and wake up regularly
• Who got similar results to Siffre?

  Aschoff and Wever
• What was the procedure in Aschoff and Wever's study?

  Participants spent four weeks in a WW2 bunker deprived of natural light
• What did Aschoff and Wever find?

  All but one participant displayed a circadian rhythm between 24 and 25 hours
• What do Siffre's and Aschoff and Wever's findings suggest?

  The 'natural' sleep/wake cycle may be slightly longer than 24 hours but is entrained by exogenous zeitgebers
• Whose study suggests the existence of a free-running circadian rhythm not overridden by exogenous zeitgebers?

  Folkard et al.
• What was the procedure in Siffre's study?

  Spent two months in a cave and then another six months in a cave
• What was the procedure in Folkard et al.'s study?

  12 people lived in a cave for three weeks, going to bed when a clock said 11:45 pm and waking at 7:45 am - researcher sped up clock secretly
• What did Folkard et al. find?

  One participant was able to comfortably adjust to the new regime