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Biorhythm regulation


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Biorhythm regulation

  1. 1. Endocrine SystemPart 6: Biorhythm Regulation
  2. 2. Pineal Gland Pine cone shaped gland Size: 5-8 mm
  3. 3. Pineal Gland
  4. 4. Pineal Gland Function light absorbed by the retina is transferred and interpreted by suprachiasmatic nucleus (SCN)
  5. 5. Suprachiasmatic Nucleus SCN in the hypothalamus
  6. 6. Suprachiasmatic Nucleus
  7. 7. Pineal Gland Function SCN passes information onto pineal gland Pineal gland synthesizes and secretes melatonin
  8. 8. Melatonin Peptide hormone Made from amino acid tryptophan
  9. 9. Melatonin Levels Production inhibited by light exposure Secretion decreases during the day, increases at night Amount of light detected by SCN is inversely proportional to the amount of melatonin produced in the evening
  10. 10. Melatonin Levels amount secreted depends on the length of the night
  11. 11. Melatonin Levels high in infancy and childhood decreases with age
  12. 12. Melatonin Effects Decreases motor activity Induces fatigue Lowers body temperature
  13. 13. Circadian Rhythm Light-dependent rhythms Synchronize rhythm with outside world Daily rhythms: light-dark cycles Cues from eyes:  visual information  light received
  14. 14. Melatonin & Sleep Cycles Regulates the sleep-wake cycle  increased melatonin increases sleepiness Can be used to treat sleep disorders:  Insomniac  Shift workers  Jet lag  Blind people (can’t set circadian rhythm because can’t detect light with eyes)
  15. 15. Melatonin & Seasons Melatonin levels change with the seasons  what happens above the Arctic circle? Correlates to seasonal activities in animals  winter have longer nights  thus increased levels of melatonin signals winter season
  16. 16. Melatonin & Reproduction Suppresses libido by inhibiting secretion of the gonadotropins (LH & FSH) Inhibits GnRH affecting reproductive organs Regulates fertility during mating season  Animals with breeding seasons in the spring/summer (long days, short nights) will have reproduction repressed by melatonin (e.g. horse)  Animals who breed during fall/winter (short days, long nights) will have increased frequency of mating with increased melatonin (e.g. sheep)  mating season can be artificially induced