Thermoregulation

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Thermoregulation

  1. 1. ThermogulatorAdaptationsThermoregulation
  2. 2. ThermoregulationRegulation of internal body temperatureMaintenance of body temperature within anacceptable range
  3. 3. Example of Thermoregulatorhumans live in climates of varying temperature butable to maintain constant body temperature
  4. 4. Cold & Warm bloodedWhy are the terms for classifying organismsinto cold-blooded and warm-bloodedinaccurate?What are the correct terms?What is the advantage of being able toregulate body temperature?What is the disadvantage of regulating bodytemperature?
  5. 5. ThermoregulationEctotherm EndothermMetabolic rate Low HighHeatgenerationToo little towarm bodyEnough to keepbody warmInternal bodytemperatureDetermined byenvironmentStable, regardless ofexternalfluctuationsExampleorganismsfish, reptiles,amphibiansmammals, birds
  6. 6. Advantage of Thermoregulation1. High levels of aerobic metabolism Perform vigorous activity for longer periods E.g. flight2. Enable terrestrial living Extreme temperature fluctuation on land(opposed to aquatic)
  7. 7. Disadvantage of Thermoregulation1. Energetically expensive Example: at rest, body temperature 20oC humans: 1300-1800 kcal/day alligator: 60kcal/day1. Need to consume more food
  8. 8. Methods of ThermoregulationAdaptations:Physical adaptationsBehavioral adapationsCirculatory adaptationPhysiological changes:Rate of heat exchangeEvaporative heat loss (cooling)Rate of heat productionRate of metabolic heat production
  9. 9. Physical AdaptationsInsulationhair, fur, feathersfat located just beneath the skinhttp://www.freakingnews.com/Fat-Cat-Pics-24390.asp
  10. 10. Behavioral AdaptationsGrossMovementHuddling:decreasesurface area& heat lossRe-locating:Findingshaded areasBasking insunMigrationMarine Iguana(Amblyrhynchus cristatus).Basking in the sun.http://life-sea.blogspot.ca/2011/08/life-of-marine-iguana.html
  11. 11. Thermoregulator?Q: Are ectothermsthermoregulators?A: Yes if bodytemperature is beingregulated, even if themechanism is abehavioural adaptation(I.e. moving to awarmer location)http://29.media.tumblr.com/eiAbVQY7Vplg25wgYVcAt9P0o1_500.jpg
  12. 12. Behavioural Adaptations Torpor: state of low metabolic activity Applied during environmental extremes Conserves energy Hibernation: long-term torpor Survive long periods of cold temperatures on limitedsupplies of energy Body temperature declines Estivation: summer torpor Survive long periods of high temperatures or whenwater is scarce Example: Lung Fish (http://www.youtube.com/watch?v=ZUsARF-CBcI)
  13. 13. Circulatory AdaptationCounter current heat exchange(Fig. 44.5)
  14. 14. Countercurrent Heat ExchangeArteries carrying warm blood in limbs (andwings) are in close contact with veinsconveying cool blood back toward the trunkVenus blood approaching torso will be almostas warm as the body core
  15. 15. Methods of ThermoregulationAdaptations:Physical adaptationsBehavioral adaptationsCirculatory adaptationsPhysiological changes:Rate of heat exchangeEvaporative heat loss (cooling)Rate of heat productionRate of metabolic heat production
  16. 16. Rate of Heat ExchangeRegulated by blood vessel sizeVasoconstrictionVasodilation
  17. 17. Rate of Heat ExchangeVasoconstrictionDecrease superficial blood vessel diameterDecrease blood flow to surface, cooling skinReduce heat loss from bodyVasodilationIncrease in diameter of blood vessels near bodysurfaceIncrease blood flow to surface, warming skinTransfers body heat to environment
  18. 18. Extreme ColdWhy does your body allow you to get frostbite?What happens to body temperature withhypothermia? Why is hypothermia such aconcern but frost bites aren’t?
  19. 19. CryopreservationSuspending life due to freezingfrozen cytosol can expand to break the cell membraneNeed to dehydrate cells before freezingOnly certain cell types can be cryopreservedSemenBlood (special cells for transfusion, or stem cells)Tissue samples like tumors and histological cross sectionsHuman eggsHuman embryos that are 2, 4 or 8 cells
  20. 20. Frozen Wood FrogsKenneth B. Storey – Carleton UniversityVideo: http://www.youtube.com/watch?v=UvCdOXG2rPo (1:56)
  21. 21. Evaporative Heat Loss (cooling)Water absorbs heat when it evaporateSweating evaporates water across skin thusremoving heat from body
  22. 22. Rate of Heat ProductionSkeletal muscle contractionresults in shivering whichgenerates more heatPhysical evidence: goosebumps
  23. 23. Rate of Metabolic HeatProductionHormones can cause mitochondria toincrease metabolic activity to produce heatinstead of ATPBrown adipose (fat) tissue metabolismFat cells have high concentration of mitochondriato generate heatnewborns have many of these cells; don’t shiverApplies only to endotherms
  24. 24. Brain: The body’s thermostatSensory receptor (input):Thermoreceptors on skin sense temperatureIntegration: hypothalamusContains neurons that respond to changes inbody temperature above and below thenormal rangeEffector (output):Behavioural changesPhysiological changes (heat exchange,evaporative cooling, heat production,metabolic rate)
  25. 25. Cold Response:Physiological ChangesEvaporativeCoolingRate of heatexchangeRate of heatproduction
  26. 26. Cold Response:Physiological ChangesRate of heat exchange decreases:Vasoconstriction of blood vessels near skinless blood to skin = less heat lossBlood redirected to torso (organs)Rate of heat production increases:muscles contractshivering generates heatRate of metabolic heat production increases:brown adipose (fat) tissue metabolism
  27. 27. Heat Stress Response:Physiological Changeshigh body temperaturehypothalamus nerve pathwaybody temperaturedropsblood vessels dilate;increased blood flow;heat leaves skinsweat glands induced;sweat evaporation
  28. 28. Physiological ThermoregulatoryResponsehttp://www.bbc.co.uk/bitesize/intermediate2/biology/images/200/113_bitesize_intermediate2_biology_subunit5_metabolic_rate.png http://bioserv.fiu.edu/~walterm/B/homeostasis/lectur33.jpg
  29. 29. Physiological ThermoregulatoryResponse SummaryStimulus DecreasetemperatureIncreasetemperatureBloodvesselsSkeletalmusclesSweatglands
  30. 30. Physiological ThermoregulatoryResponse SummaryStimulus DecreasetemperatureIncreasetemperatureBloodvesselsVasoconstriction:decrease blood flowVasodilation:increase blood flowSkeletalmusclesShiveringSweatglandsDecrease productionof sweatEvaporative cooling:increase sweat
  31. 31. Fig. 44.10

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