circadian

• What do circadian rhythms refer to?

  Cyclical changes in biological processes
• How long does it take to complete one full cycle of a circadian rhythm?

  About 24 hours
• What characterizes a circadian rhythm during a full day/night period?

  One peak and one trough
• What is a chronotype?

  A natural time to wake and rest
• What largely determines whether someone is a night owl or early bird?

  Genetics
• How does the sleep-wake cycle relate to circadian rhythms?

  It is an example of a circadian rhythm
• When do cortisol levels peak and trough?

  Peak in the evening, trough at night
• What happens to concentration and alertness for night shift workers?

  They experience a trough during the night
• What happens in the absence of exogenous zeitgebers?

  The body's endogenous pacemaker free runs
• What is the typical circadian rhythm duration when only the SCN controls it?

  Usually just under 25 hours
• What would happen to daily routines without exogenous zeitgebers?

  Days would be longer than 24 hours
• How does the SCN respond to changing light levels?

  It coordinates biological processes
• What hormone does the pineal gland secrete during low light periods?

  Melatonin
• What effect does increased light have on melatonin secretion?

  It inhibits melatonin secretion
• What does the research by Siffre (1962) aim to investigate?

  The body's endogenous pacemaker without exogenous zeitgebers
• What was the method used by Siffre in his study?

  Spent 6 months in a cave
• What was the average sleep-wake cycle duration observed by Siffre?

  25 hours
• What did Siffre mistakenly believe about his time in the cave?

  He thought he was there for 151 days
• What does Siffre's study support regarding endogenous pacemakers?

  They can regulate a consistent sleep/wake cycle
• What is a limitation of Siffre's case study?

  Small sample size limits generalizability
• What is a confounding variable in Siffre's study?

  Use of artificial light
• What was the aim of Aschoff and Wever's bunker experiments?

  To study circadian rhythms in controlled conditions
• How long did participants stay in the bunker during Aschoff and Wever's study?

  4 weeks
• What was a significant finding from Aschoff and Wever's study?

  Most lived on a cycle just over 24 hours
• What limitation does Aschoff and Wever's study have regarding generalizability?

  Only students were studied
• What was the aim of Folkard et al's study?

  To investigate the influence of endogenous pacemakers
• What was the unique aspect of the clock in Folkard et al's study?

  The clock was changed to a 22-hour day
• What was a key finding from Folkard et al's study?

  Only one participant adapted to the new rhythm
• What does research into circadian rhythms help improve in drug treatments?

  Understanding of pharmacokinetics
• How can drug administration timing benefit patients?

  Increases efficacy and reduces side effects
• What is a practical application of understanding circadian rhythms?

  Improving health of shift workers
• What negative implications do night shift workers face?

  Circadian trough at about 5 am
• What classification did the WHO give to shift work in 2007?

  Probable carcinogen
• What individual differences affect chronotype?

  Genetics and age
• How much can circadian cycles vary between individuals?

  By 13 to 65 hours
• How did Siffre's circadian rhythm change with age?

  Followed a 48-hour cycle at 60 years
• What did DeCoursey et al. (2002) demonstrate using chipmunks?

  Influence of the SCN on sleep/wake cycle
• What happened to the chipmunks after SCN connections were destroyed?

  Their sleep/wake cycle disappeared
• What ethical issue arises from DeCoursey et al.'s study?

  Harm caused to the chipmunks
• What did Ralph et al. find regarding genetically bred hamsters?

  They had a 20-hour circadian rhythm