endogenous pacemakers and exogenous zeitgebers

• exogenous zeitgebers


  external cues that may affect or entrain our biological rhythms, such sd influence of light
• endogenous pacemakers


  internal body clocks that regulate many of our biological rhythms, such as the influence of SCN on the sleep/ wake cycle
• exogenous zeitgebers 


  light- Campbell and Murphy- shone light pad on back of knees

  social cues- babies rhythms are entrained by bedtimes and mealtimes
• endogenous pacemakers 


  the SCN- receives info about light directly

  animal studies + the SCN- Decoursey et al- sleep/ wake cycle disappeared- SCN destroyed

  the pineal gland + melatonin- the SCN passes info to the pineal gland that controls melatonin
• evaluation


  weakness: ethics in animal studies

  • DeCoursey study harmed animals

  weakness: methological studies

  • light pas study findings not replicated+ isolating one zeitgeber may be unrealistic