circadian rhythms L9

• What are biological rhythms?

  Cyclical changes in the behavior of biological systems
• Why have biological rhythms evolved?

  Because the environment exhibits cyclical changes
• What is the most well-known biological rhythm?

  The circadian rhythm
• What does a circadian rhythm repeat approximately every?

  Every 24 hours
• What biological processes are influenced by circadian rhythms?

  Alertness, body temperature, and hormone release
• Why is the study of circadian rhythms important?

  It is crucial for understanding basic biological processes and human health
• Who conducted a case study to understand circadian rhythms?

  Michel Siffre
• What was the environment like for Michel Siffre during his study?

  He was isolated in a cave with no natural light or external cues
• What did Siffre do to regulate his rhythms in the cave?

  He slept, woke, and ate when he felt the need
• What did Siffre's findings reveal about circadian rhythms when isolated from external cues?

  They tend to drift and do not readily adapt to a 24-hour clock
• What is the primary pacemaker of the body's circadian rhythms?

  The suprachiasmatic nuclei (SCN)
• How does light affect the SCN?

  Light stimulates the SCN, which sends messages about light levels to the body
• What role does the SCN play in hormone production?

  It alters the production of hormones and neurotransmitters in a cyclical fashion
• What does the circadian rhythm dictate besides sleep and wake times?

  When we should eat and drink
• What is the period of maximum alertness according to the circadian rhythm?

  Between 2am and 7pm
• When is the need for sleep and rest greatest?

  Between 1pm and 6am
• How does body temperature relate to sleep and wakefulness?

  Body temperature fluctuates and influences sleep and wakefulness
• When does the minimum core body temperature occur?

  Between 2am and 4am
• What happens to core body temperature during sleep?

  It gradually declines
• What is the role of melatonin in circadian rhythms?

  It is produced primarily at night and follows a circadian pattern
• What did Hough et al. (1987) find about circadian rhythms in polar regions?

  They varied and sometimes drifted due to extreme daylight conditions
• What did Duffy et al. (2001) suggest about individual differences in circadian rhythms?

  Individuals can have different cycle lengths and preferences for sleep times
• What flaw did early research studies of circadian rhythms have?

  Participants were not isolated from all external cues
• How can research on circadian rhythms be improved?

  By using artificially consistent lighting to minimize environmental cues
• What is chronotherapeutics?

  The study of how timing affects drug treatments
• How can circadian rhythms affect drug effectiveness?

  Timing of medication can modify its effects on patients
• What did Buhr et al. (2010) suggest about temperature and circadian rhythms?

  Temperature may control the body clock rather than light
• How does temperature influence the SCN?

  Changes in body temperature set a rhythm in the SCN
• What is the relationship between the SCN and other body clocks?

  Other body clocks provide feedback to the body and influence overall rhythms
• 
  

  The internal biological processes that occur in living organisms over a 24-hour period, even in the absence of external cues like light and darkness.
• Siffre's findings


  When isolated from external cues, Siffre's circadian rhythms tended to drift and did not readily adapt to a 24-hour clock.
• Drift


  The tendency of a free-running rhythm to slowly change its period over time, meaning the rhythmic pattern becomes longer or shorter than 24 hours.
• Free-running rhythms


  A condition where a living organism's internal biological processes do not synchronize with the external environment, often resulting in a rhythmic period that is not exactly 24 hours.