Biological Rhythms

1. Biological Rhythms

2. Animal can predict the future?

4. 2 criteria for existence of a clock • Behavior rhythmic • Rhythm persists without external cues • done by isolation • eclosion of fruit flies in dark

5. Biological Clock “are internal timing mechanisms that involve both self-sustaining physiological pacemakers and cyclic synchronizer (zeitgerbers)” suprachiasmatic nuclei

8. Clock properties • Persistence in constant conditions • Stability of period length • Entrainment by environmental cycles • Period control : daily adjustment of the free-running period of the natural day-night cycle • Phase control : adjustment to a new light-dark cycle

9. Advantages of biological clocks • Anticipation of environmental change • Synchronization of behaviour with an event that cannot be sensed directly • Continuous measurement of time

10. Types of Rhythms Biological clocks for ALL of the earth’s natural cycle • dialy tides (1/2 lunar day, 12.4 hr) • solar day (24 hr) • month • year • many years

11. Internal Rhythms • High frequency • period shorter than 30 min • ex :- heart rate, respiration rate • Ultradian rhythms • longer than 30 min, shorter than 20 hr • ex :- fluctuation of growth hormone, body temperature in cat

12. Internal Rhythms (cont) • Circadian Rhythms • approximately 24 hr long • ex :- cellular and endocrinological parameters hepatic aminotransferase in swine • age

14. Internal Rhythms (cont) • Infradian Rhythms • period length > 28 hr but < 2.5 days • Circatrigentian rhythms, ~30 days period • ex :- sexual cycle of polyestrous domestic animals

15. Internal Rhythms (cont) • Annual Rhythms • annual cycle or seasonal cycle • ex :- Horse begin to show estrus as long day season Sheep begin to show estrus as short day season

16. Internal Rhythms (cont) • Parasitic Rhythms • Dirofilaria immitis ; canine heart worm • microfilaria are most active and most found in peripheral circulation in the evening

17. External Influences • Circadian Rhythms • are endogeneous, persists under conditions of constant light or constant darkness • usually influenced by external factors :- light, barometic pressure, drugs

18. External Influences (cont) • Light • hamster entrain to 12 hr light - 12 hr dark • not to 6 hr light - 30 hr dark • red light • Barometric Pressure • horse, swine --> show high level of activity before storms

19. External Influences (cont) • Drugs • drug effect the body rhythms --> caffeine, theophyline • Jet-lag or sleep disturbance --> melatonin, benzodiazepines

20. Biological basis for entraining rhythms • Cyclic variations within the cells • cyclic variation in the macromolecules within the cells --> inhibitor of protein synthesis • Suprachiasmatic Nucleus • master clock

21. Biological basis for entraining rhythms • Pineal gland • contain photoreceptor cell --> 3rd eye • synchronize circadian rhythms :- release hormone, neurotransmitters • sensory function in fish, amphibian, reptiles

22. Biological basis for entraining rhythms • Pineal gland • in mammals, lack of photosensory cells • produce melatonin • Higher quantity in plasma and CSF at night • antigonadotrophic effect in long day breeder (horse) • progonadotrophic effect in short day breeder (sheep)

24. Neurological Basis of Sleep • Function • conserve energy • replenishing neurotransmitter • Types of Sleep • slow wave sleep (SWS) or quick sleep • synchronous wave of high voltage, slow activity

25. Neurological Basis of Sleep • Types of Sleep (cont) • rapid eye movement sleep (REM) or active sleep or sleep of body • low voltage • fast activity similar that seen in wakeful state • little muscle activity --> sleep of body • so difficult to arouse than in SWS falling asleep -- serotonin may induce drowsiness and sleep

27. Pattern of sleep and activity

28. Pattern of sleep and activity • Dogs • eye may open / close • REM may accompanied by leg movement, vocalization and apnea or polypnea • during day, caged dog -- more than 1/2 their time sleeping, 1/4 standing

29. Pattern of sleep and activity • Cats • like a dog, caged cat -- spend 10 hr / day sleeping • during REMS, the nictitating membrane cover the eye • farm cat spent 40% of time asleep, most of it at night

30. Pattern of sleep and activity • Pigs • spend more time resting than any other domestic animal • 19 hr / day -- recumbent • 5 hr / day -- asleep • only 1/3 hr / day are spent in other activity -- drinking, walking, playing or fighting • most domestic pig :- diurnal

31. Pattern of sleep and activity • Horses • able to drowse and even to engage in SWS while standing • during the day : horse awake 88% of time, (alert) • unlike ruminants, show tachecardia, leg movement and increase respiration rate during REMS

33. Pattern of sleep and activity • Cattle • essentially diurnal • major activities are grazing, ruminating and resting • gazing time is inversely proportional to the quality of the pasture (5-8 hr/day)

35. Pattern of sleep and activity • Sheep • spend 50% of daylight hour grazing • travel 4 - 14 km a day, 0.8 km a day on pasture

36. Pattern of sleep and activity • Common Problems • hyperactivity • nocturnal wakefulness