Key words

•  Endogenous Pacemakers... (internal factors)

   

  ­These are part of the internal organism. Internal influences which affect the body clocks that regulate biological rhythms, such as the sleep wake cycle. Examples of these are the role of the SCN and the secretion of melatonin from the pineal gland.
•  Exogenous Zeitgebers...(external factors)

   

  ­These are external cues in the environment that may affect our biological rhythms. E.g. the influence of light, exercise, meal time etc. on the sleep/wake cycle.