endogenous pacemakers + sleep/wake cycle

• Suprachiasmatic nucleus (SCN)

  • bundle of nerves in hypothalamus
  • primary pacemaker - maintains circadian rhythm
  • nerve fibres connected to eye cross in optic chiasm - receives info
  • passed info to pineal gland - more melatonin production

  animal studies

  • DeCoursey et al: destroyed 30 chipmunk’s SCN, Watched 80 days in habitat - sleep/wake cycle dissappeared
  • Ralph et al: bred mutant hamsters with 20 hour sleep/wake, SCN from foetal tissue transplanted into normal hamster - normal -> 20 hour
• endogenous pacemakers evaluations

  • W: overestimated SCN importance: other rhythms in many organs + cells - change mice feed pattern, change in liver cell rhythm up to 12 hour - no affected on SCN
  • W: isolation: total isolation stuides rare + artifical light + everyday they interact