Pacemakers and Zeitgebers

• What are endogenous pacemakers?

  Internal biological clocks that regulate our bodily cycles
• What is an example of an endogenous pacemaker?

  Suprachiasmatic nucleus (SCN)
• Where is the SCN located?

  The SCN is located in the hypothalamus of the brain and slightly above the eye cross in order to receive information about light to regulate cycles
• Which gland does the suprachiasmatic nucleus send signals to?

  The pineal gland
• What does the pineal gland secrete?

  Melatonin
• Who destroyed the SCNs of chipmunks and studied their sleep cycles in their natural environment?

  DeCoursey
• What are the strengths of endogenous pacemakers?

  • Research support - Siffre, menstrual cycles
  • Scientific methods
• What are the limitations of endogenous pacemakers?

  • Ethical issues with animal studies
  • Extrapolation issues with animal studies
• Who studied mutant hamsters with 20 hour sleep cycles by transferring cells to normal hamsters?

  Ralph
• Who studied exogenous zeitgebers by shining light pads on the backs of knees?

  Campbell and Murphy
• What did Campbell and Murphy find?

  Sleep cycles could be disturbed when skin receptors sense light (the exogenous zeitgeber)
• What is a real-life example of exogenous zeitgebers in action?

  Newborn babies being entrained into both a sleep cycles and a mealtime cycle by parents
• What are strengths of the exogenous zeitgebers?

  • Research support - Campbell and Murphy
  • Real-life application - newborn babies
  • Both exo zeitgebers and endo pacemakers are interactionist together
• What are the limitations of exogenous zeitgebers?

  • Participant variables in Campbell and Murphy’s study
  • Doesn’t consider nature on its own
  • Artificial environment in Campbell’s study