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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
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
Biological Clock

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

suprachiasmatic nuclei

clock properties
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
advantages of biological clocks
Advantages of biological clocks
  • Anticipation of environmental change
  • Synchronization of behaviour with an event that cannot be sensed directly
  • Continuous measurement of time
types of rhythms
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
internal rhythms
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
internal rhythms cont
Internal Rhythms (cont)
  • Circadian Rhythms
    • approximately 24 hr long
    • ex :- cellular and endocrinological parameters hepatic aminotransferase in swine
      • age
internal rhythms cont14
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
slide15
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
slide16
Internal Rhythms (cont)
  • Parasitic Rhythms
    • Dirofilaria immitis ; canine heart worm
      • microfilaria are most active and most found in peripheral circulation in the evening
slide17
External Influences
  • Circadian Rhythms
    • are endogeneous, persists under conditions of constant light or constant darkness
    • usually influenced by external factors :- light, barometic pressure, drugs
slide18
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
slide19
External Influences (cont)
  • Drugs
    • drug effect the body rhythms --> caffeine, theophyline
    • Jet-lag or sleep disturbance --> melatonin, benzodiazepines
slide20
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
slide21
Biological basis for entraining rhythms
  • Pineal gland
    • contain photoreceptor cell --> 3rd eye
    • synchronize circadian rhythms :- release hormone, neurotransmitters
    • sensory function in fish, amphibian, reptiles
slide22
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)
slide24
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
slide25
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

slide28
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
slide29
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
slide30
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
slide31
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
slide33
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)
slide35
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
slide36
Pattern of sleep and activity
  • Common Problems
    • hyperactivity
    • nocturnal wakefulness
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