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นาฬิกาทางชีววิทยา

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นาฬิกาทางชีววิทยา

  1. 1. Biological Rhythms
  2. 2. Animal can predict the future?
  3. 4. 2 criteria for existence of a clock <ul><li>Behavior rhythmic </li></ul><ul><li>Rhythm persists without external cues </li></ul><ul><ul><li>done by isolation </li></ul></ul><ul><ul><li>eclosion of fruit flies in dark </li></ul></ul>
  4. 5. Biological Clock <ul><li>“ are internal timing mechanisms that involve both self-sustaining physiological pacemakers and cyclic synchronizer (zeitge r bers)” </li></ul><ul><li>suprachiasmatic nuclei </li></ul>
  5. 8. Clock properties <ul><li>Persistence in constant conditions </li></ul><ul><li>Stability of period length </li></ul><ul><li>Entrainment by environmental cycles </li></ul><ul><ul><li>Period control : daily adjustment of the free-running period of the natural day-night cycle </li></ul></ul><ul><ul><li>Phase control : adjustment to a new light-dark cycle </li></ul></ul>
  6. 9. Advantages of biological clocks <ul><li>Anticipation of environmental change </li></ul><ul><li>Synchronization of behaviour with an event that cannot be sensed directly </li></ul><ul><li>Continuous measurement of time </li></ul>
  7. 10. Types of Rhythms <ul><li>Biological clocks for ALL of the earth’s natural cycle </li></ul><ul><li>dialy tides (1/2 lunar day, 12.4 hr) </li></ul><ul><li>solar day (24 hr) </li></ul><ul><li>month </li></ul><ul><li>year </li></ul><ul><li>many years </li></ul>
  8. 11. Internal Rhythms <ul><li>High frequency </li></ul><ul><ul><li>period shorter than 30 min </li></ul></ul><ul><ul><li>ex :- heart rate, respiration rate </li></ul></ul><ul><li>Ultradian rhythms </li></ul><ul><ul><li>longer than 30 min, shorter than 20 hr </li></ul></ul><ul><ul><li>ex :- fluctuation of growth hormone, body temperature in cat </li></ul></ul>
  9. 12. Internal Rhythms (cont) <ul><li>Circadian Rhythms </li></ul><ul><ul><li>approximately 24 hr long </li></ul></ul><ul><ul><li>ex :- cellular and endocrinological parameters hepatic aminotransferase in swine </li></ul></ul><ul><ul><ul><li>age </li></ul></ul></ul>
  10. 14. Internal Rhythms (cont) <ul><li>Infradian Rhythms </li></ul><ul><ul><li>period length > 28 hr but < 2.5 days </li></ul></ul><ul><ul><li>Circatrigentian rhythms , ~30 days period </li></ul></ul><ul><ul><li>ex :- sexual cycle of polyestrous domestic animals </li></ul></ul>
  11. 15. Internal Rhythms (cont) <ul><li>Annual Rhythms </li></ul><ul><ul><li>annual cycle or seasonal cycle </li></ul></ul><ul><ul><li>ex :- Horse begin to show estrus as long day season Sheep begin to show estrus as short day season </li></ul></ul>
  12. 16. Internal Rhythms (cont) <ul><li>Parasitic Rhythms </li></ul><ul><ul><li>Dirofilaria immitis ; canine heart worm </li></ul></ul><ul><ul><ul><li>microfilaria are most active and most found in peripheral circulation in the evening </li></ul></ul></ul>
  13. 17. External Influences <ul><li>Circadian Rhythms </li></ul><ul><ul><li>are endogeneous, persists under conditions of constant light or constant darkness </li></ul></ul><ul><ul><li>usually influenced by external factors :- light, barometic pressure, drugs </li></ul></ul>
  14. 18. External Influences (cont) <ul><li>Light </li></ul><ul><ul><li>hamster entrain to 12 hr light - 12 hr dark </li></ul></ul><ul><ul><li>not to 6 hr light - 30 hr dark </li></ul></ul><ul><ul><li>red light </li></ul></ul><ul><li>Barometric Pressure </li></ul><ul><ul><li>horse, swine --> show high level of activity before storms </li></ul></ul>
  15. 19. External Influences (cont) <ul><li>Drugs </li></ul><ul><ul><li>drug effect the body rhythms --> caffeine, theophyline </li></ul></ul><ul><ul><li>Jet-lag or sleep disturbance --> melatonin, benzodiazepines </li></ul></ul>
  16. 20. Biological basis for entraining rhythms <ul><li>Cyclic variations within the cells </li></ul><ul><ul><li>cyclic variation in the macromolecules within the cells --> inhibitor of protein synthesis </li></ul></ul><ul><li>Suprachiasmatic Nucleus </li></ul><ul><ul><li>master clock </li></ul></ul>
  17. 21. Biological basis for entraining rhythms <ul><li>Pineal gland </li></ul><ul><ul><li>contain photoreceptor cell --> 3 rd eye </li></ul></ul><ul><ul><li>synchronize circadian rhythms :- release hormone, neurotransmitters </li></ul></ul><ul><ul><li>sensory function in fish, amphibian, reptiles </li></ul></ul>
  18. 22. Biological basis for entraining rhythms <ul><li>Pineal gland </li></ul><ul><ul><li>in mammals, lack of photosensory cells </li></ul></ul><ul><ul><li>produce melatonin </li></ul></ul><ul><ul><ul><li>Higher quantity in plasma and CSF at night </li></ul></ul></ul><ul><ul><ul><li>antigonadotrophic effect in long day breeder ( horse ) </li></ul></ul></ul><ul><ul><ul><li>progonadotrophic effect in short day breeder ( sheep ) </li></ul></ul></ul>
  19. 24. Neurological Basis of Sleep <ul><li>Function </li></ul><ul><ul><li>conserve energy </li></ul></ul><ul><ul><li>replenishing neurotransmitter </li></ul></ul><ul><li>Types of Sleep </li></ul><ul><ul><li>slow wave sleep (SWS) or quick sleep </li></ul></ul><ul><ul><ul><li>synchronous wave of high voltage, slow activity </li></ul></ul></ul>
  20. 25. Neurological Basis of Sleep <ul><li>Types of Sleep (cont) </li></ul><ul><ul><li>rapid eye movement sleep (REM) or active sleep or sleep of body </li></ul></ul><ul><ul><ul><li>low voltage </li></ul></ul></ul><ul><ul><ul><li>fast activity similar that seen in wakeful state </li></ul></ul></ul><ul><ul><ul><li>little muscle activity --> sleep of body </li></ul></ul></ul><ul><ul><ul><li>so difficult to arouse than in SWS </li></ul></ul></ul><ul><ul><li>falling asleep -- serotonin may induce drowsiness and sleep </li></ul></ul>
  21. 27. Pattern of sleep and activity
  22. 28. Pattern of sleep and activity <ul><li>Dogs </li></ul><ul><ul><li>eye may open / close </li></ul></ul><ul><ul><li>REM may accompanied by leg movement, vocalization and apnea or polypnea </li></ul></ul><ul><ul><li>during day, caged dog -- more than 1/2 their time sleeping, 1/4 standing </li></ul></ul>
  23. 29. Pattern of sleep and activity <ul><li>Cats </li></ul><ul><ul><li>like a dog, caged cat -- spend 10 hr / day sleeping </li></ul></ul><ul><ul><li>during REMS, the nictitating membrane cover the eye </li></ul></ul><ul><ul><li>farm cat spent 40% of time asleep, most of it at night </li></ul></ul>
  24. 30. Pattern of sleep and activity <ul><li>Pigs </li></ul><ul><ul><li>spend more time resting than any other domestic animal </li></ul></ul><ul><ul><li>19 hr / day -- recumbent </li></ul></ul><ul><ul><li>5 hr / day -- asleep </li></ul></ul><ul><ul><li>only 1/3 hr / day are spent in other activity -- drinking, walking, playing or fighting </li></ul></ul><ul><ul><li>most domestic pig :- diurnal </li></ul></ul>
  25. 31. Pattern of sleep and activity <ul><li>Horses </li></ul><ul><ul><li>able to drowse and even to engage in SWS while standing </li></ul></ul><ul><ul><li>during the day : horse awake 88% of time, (alert) </li></ul></ul><ul><ul><li>unlike ruminants, show tachecardia, leg movement and increase respiration rate during REMS </li></ul></ul>
  26. 33. Pattern of sleep and activity <ul><li>Cattle </li></ul><ul><ul><li>essentially diurnal </li></ul></ul><ul><ul><li>major activities are grazing, ruminating and resting </li></ul></ul><ul><ul><li>gazing time is inversely proportional to the quality of the pasture (5-8 hr/day) </li></ul></ul>
  27. 35. Pattern of sleep and activity <ul><li>Sheep </li></ul><ul><ul><li>spend 50% of daylight hour grazing </li></ul></ul><ul><ul><li>travel 4 - 14 km a day, 0.8 km a day on pasture </li></ul></ul>
  28. 36. Pattern of sleep and activity <ul><li>Common Problems </li></ul><ul><ul><li>hyperactivity </li></ul></ul><ul><ul><li>nocturnal wakefulness </li></ul></ul>

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