Endogenous pacemakers + Exogenous Zeitgebers

• What is the suprachiasmatic nucleus (SCN)?

  A tiny bundle of nerve cells in the brain
• What role does the SCN play in the body?

  It maintains circadian rhythms like sleep/wake cycle
• Where is the SCN located?

  Above the optic chiasm in the brain
• How does the SCN receive information about light?

  Through nerve fibres connected to the optic chiasm
• What happens to the biological clock when our eyes are closed?

  It adjusts to changing patterns of daylight
• What did DeCoursey et al. (2000) study demonstrate?

  SCN connections are crucial for sleep/wake cycle
• What was the outcome for the chipmunks in DeCoursey et al.'s study?

  Their sleep/wake cycle disappeared
• What does the outcome of DeCoursey et al.'s study suggest about the SCN?

  It is essential for survival and sleep patterns
• What did Ralph et al. (1990) find in their study with hamsters?

  Mutant hamsters had a 20-hour sleep/wake cycle
• What happened when SCN cells from mutant hamsters were transplanted?

  Normal hamsters adopted a 20-hour cycle
• What role does the pineal gland play in sleep?

  It produces melatonin during the night
• What is melatonin?

  A chemical that induces sleep
• How does the SCN influence the pineal gland?

  It passes information about day length and light
• What are peripheral oscillators?

  Circadian rhythms in various body organs
• Where are peripheral oscillators found?

  In organs like the liver and pancreas
• What did Damiola et al. (2000) demonstrate about feeding patterns?

  They can alter liver circadian rhythms
• What does the research suggest about the SCN and peripheral oscillators?

  Peripheral clocks can act independently of SCN
• What ethical concerns arise from animal studies like DeCoursey et al.'s?

  Animals may be exposed to harm and risk
• What are exogenous zeitgebers?

  External factors that reset biological clocks
• How do exogenous zeitgebers affect the sleep/wake cycle?

  They reset biological clocks through entrainment
• What happens to the biological clock in the absence of external cues?

  It continues to tick in a cyclical pattern
• What is the role of light as a zeitgeber?

  It resets the SCN and influences hormones
• What did Campbell and Murphy (1998) demonstrate about light?

  Light can be detected by skin receptors
• What was the effect of shining light on participants' knees?

  It deviated their sleep/wake cycle by 3 hours
• How do social cues influence infants' sleep/wake cycles?

  They help entrain circadian rhythms
• At what age do infants begin to develop circadian rhythms?

  About 6 weeks of age
• What is the effect of adult-determined schedules on infants?

  They influence mealtimes and bedtimes
• What does the interactionist system suggest about endogenous pacemakers?

  They are rarely free-running and unaffected
• What is a limitation of total isolation studies?

  They lack validity due to rarity
• What do Miles et al. (1977) illustrate about exogenous zeitgebers?

  They may not adjust internal rhythms for everyone
• What do studies in Arctic regions show about sleep patterns?

  Normal sleep patterns despite prolonged light
• What methodological issues exist in the Campbell and Murphy study?

  Findings have not been replicated and confounding variables
• What are the key components of the endogenous pacemaker system?

  • Suprachiasmatic nucleus (SCN)
  • Pineal gland and melatonin
  • Peripheral oscillators in various organs
• What are the strengths and weaknesses of animal studies in sleep research?

  Strengths:

  • Provide insights into biological mechanisms
  • Can control variables in a lab setting

  
  

  Weaknesses:

  • Ethical concerns regarding animal welfare
  • Generalizability to humans is limited