Endogenous Pacemakers and Exogenous Zeitgebers

• What are endogenous pacemakers?

  Internal mechanisms that govern biological rhythms
• What factors can alter and affect endogenous pacemakers?

  Environmental factors such as light
• How does the SCN function in relation to biological rhythms?

  It controls other biological rhythms and links to areas of the brain responsible for sleep and arousal
• How does the endogenous pacemaker govern the sleep/wake cycle?

  • SCN receives information about light from the optic nerve
  • SCN sends signals to the pineal gland
  • Increases melatonin production at night to induce sleep
  • Decreases melatonin production as light levels increase
• What are exogenous zeitgebers?

  Environmental events that reset the biological clock of an organism
• What are two types of exogenous zeitgebers?

  Social cues and light