Endogenous pacemakers & Exogenous zeitgebers

• Endogenous Pacemakers - mechanisms within the body that govern the internal, biological, bodily rhythms
• Endogenous pacemakers AO3:

  • ✅ Support for the role of the SCN - hamster studies where SCN neurons from different hamsters were transplanted & their circadian rhythms changed
  • ❌ Dangers of disrupted rhythms - teens on devices at night disrupt melatonin & affects sleep - increased rate of mood disorders
• Exogenous zeitgebers - an environmental cue that helps to regulate the biological clock in an organism
• Exogenous Zeitgebers AO3:

  • ✅ Support for the role of melanopsin - blind people still have circadian rhythms because the connection still exists between the eye & the SCN
  • ✅ Real life applications - treats seasonal affective disorder using light therapy which stimulates sunlight to reset melatonin levels
• Endogenous pacemakers:

  • Mechanisms within the body that govern the internal, biological, bodily rhythms
  • Examples are the suprachiasmatic nucleus & the pineal gland
  • The suprachiasmatic nucleus is the 'master clock' which controls other biological clocks in the body
  • The SCN is reset daily when light levels change
  • The pineal gland produces melatonin at night which induces sleep
• Exogenous zeitgebers

  • Environmental cues that help to regulate the biological clock in an organism
  • Light resets the internal biological clock daily. Melanopsin is sensitive to natural light & signals to SCN to reset daily cycle
  • Social cues ( e.g. mealtimes ) act as zeitgebers