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Biological Rhythms. Animal can predict the future?. 2 criteria for existence of a clock. Behavior rhythmic Rhythm persists without external cues done by isolation eclosion of fruit flies in dark. Biological Clock.

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2 criteria for existence of a clock l.jpg
2 criteria for existence of a clock

  • Behavior rhythmic

  • Rhythm persists without external cues

    • done by isolation

    • eclosion of fruit flies in dark


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Biological Clock

“are internal timing mechanisms that involve both self-sustaining physiological pacemakers and cyclic synchronizer (zeitgerbers)”

suprachiasmatic nuclei


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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


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Advantages of biological clocks

  • Anticipation of environmental change

  • Synchronization of behaviour with an event that cannot be sensed directly

  • Continuous measurement of time


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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


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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


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Internal Rhythms (cont)

  • Circadian Rhythms

    • approximately 24 hr long

    • ex :- cellular and endocrinological parameters hepatic aminotransferase in swine

      • age


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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


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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


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Internal Rhythms (cont)

  • Parasitic Rhythms

    • Dirofilaria immitis ; canine heart worm

      • microfilaria are most active and most found in peripheral circulation in the evening


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External Influences

  • Circadian Rhythms

    • are endogeneous, persists under conditions of constant light or constant darkness

    • usually influenced by external factors :- light, barometic pressure, drugs


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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


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External Influences (cont)

  • Drugs

    • drug effect the body rhythms --> caffeine, theophyline

    • Jet-lag or sleep disturbance --> melatonin, benzodiazepines


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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


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Biological basis for entraining rhythms

  • Pineal gland

    • contain photoreceptor cell --> 3rd eye

    • synchronize circadian rhythms :- release hormone, neurotransmitters

    • sensory function in fish, amphibian, reptiles


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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)


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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


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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



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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


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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


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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


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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


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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)


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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


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Pattern of sleep and activity

  • Common Problems

    • hyperactivity

    • nocturnal wakefulness


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