Biological rhythms

• What are biological rhythms?

  Cyclical changes in biological systems due to environmental cyclic changes
• What are the three types of biological rhythms?

  • Circadian rhythms: cycles occurring once every 24 hours
  • Infradian rhythms: cycles taking longer than 24 hours
  • Ultradian rhythms: cycles occurring more than once every 24 hours
• What regulates biological rhythms?

  Endogenous pacemakers and exogenous zeitgebers
• What is the core body temperature variation over a day?

  • Lowest at 4am: 36°C
  • Highest at 6pm: 38°C
  • Varies by about 2 degrees Celsius
• How does core body temperature affect cognitive abilities?

  Internally warmer temperatures lead to better performance
• What did Gupta (1991) find regarding IQ performance?

  Improved IQ performance at 7pm compared to 2pm and 9am
• What dictates the sleep-wake cycle?

  The circadian rhythm
• What are the exogenous zeitgebers that influence sleep-wake cycles?

  Light and dark
• How does the circadian system respond to alterations in sleep schedules?

  It becomes out of balance
• How do teenagers' circadian rhythms compare to adults'?

  Teenagers' rhythms typically begin 2 hours later
• What were the outcomes of Monkseaton High School's later school day experiment?

  • Positive academic outcomes
  • Improved health outcomes
  • Students were nicer to each other
• What did Michel Siffre do to investigate biological rhythms?

  Spent extended periods underground
• What was Siffre's free-running biological rhythm duration?

  Around 25 hours
• What does Siffre's study suggest about natural circadian rhythms?

  They can persist without external cues but are slightly longer than 24 hours
• What is a limitation of Siffre's study regarding population validity?

  It is based on a single individual
• What is a potential extraneous variable in Siffre's study?

  Using a lamp that mimics night and day
• What are the strengths and weaknesses of Siffre's case study?

  Strengths:

  • Provides insight into biological rhythms without external cues

  Weaknesses:

  • Low population validity
  • Potential extraneous variables affecting results
• What did Folkard (1985) study demonstrate about circadian rhythms?

  Participants struggled to adjust to a sped-up clock
• What ethical issue arose in Folkard's study?

  Participants were not informed about the clock manipulation
• What are the practical applications of understanding circadian rhythms in employment?

  • Shift work can lead to desynchronization of circadian rhythms
  • Increased risk of accidents and health issues
  • Educating employers can prevent accidents and improve health
• How can understanding circadian rhythms improve medical treatments?

  • Helps determine optimal times for drug administration
  • Can increase efficacy of treatments for various disorders
• What is a significant individual difference in sleep-wake cycles?

  Some cycles can vary from 13 to 65 hours
• What is the main endogenous pacemaker in the body?

  The Suprachiasmatic Nucleus (SCN)
• What role does the SCN play in circadian rhythms?

  It maintains circadian rhythms by receiving light information
• How does the SCN communicate with the Pineal Gland?

  By passing information about light levels
• What chemical does the Pineal Gland produce?

  Melatonin
• What do studies of individuals in the Arctic suggest about the SCN?

  It regulates circadian rhythms even without external cues
• What did Decoursey et al's study on chipmunks demonstrate?

  Destruction of SCN connectors led to loss of sleep-wake cycles
• What ethical concern is raised by Decoursey et al's study?

  Chipmunks were not protected from harm
• What does the term zeitgeber mean?

  Time-giving
• What is entrainment in the context of biological rhythms?

  Synchronization of internal body clock rhythms to external cues
• What are the examples of exogenous zeitgebers?

  1. Light: Resets the internal biological clock
  2. Social cues: Mealtimes and social activities influence rhythms
• How do light levels affect the SCN?

  Receptors in the SCN are sensitive to light changes
• What did Miles et al's study suggest about blind individuals?

  76% have sleep-wake disorders, indicating EPs alone cannot maintain a 24-hour rhythm
• How do social cues affect sleep-wake cycles in infants?

  Infants learn their wake/sleep cycle from social stimuli