Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Energy and ThermoregulationMaintaining internal environments: Challenge for all living environmentsRegulators: use internal control mechanisms to regulate internal change in the face of fluctuations in the external environments.Conformers: allows internal environment to conform to external changes (for a particular environmental variable)Regulating and conforming are extremes of a continuum: Organisms may conform to some environmental factors and regulate others. e.g. fish – thermoconformers, osmoregulators.Homeostasis (steady state): Maintaining relatively steady internal environment even when external environment changes significantly. Dynamic equilibrium: external factors try to change internal environment, internal control mechanisms oppose such changes.Body temperature: 37oCpH: 7.4blood glucose: 90mg/100mL of bloodMechanisms of homeostasis:Set point: the desired temperature (variable)Stimulus: fluctuations in the variableSensor: detect stimulus and triggers an appropriate changeResponse: activity that helps return the variable to the set pointHome heating system as an example of homeostasisDo you see the machanism of homeostasis here ?Negative feedback loop: response that reduces the stimulus. (exercise and sweting)Positive feedback loop: responses amplify the stimulus (labor)Regulated changes of setpoint: e.g. temperatures change when asleep and awake, hormone levels in women’s menstrual cycleAcclimatization: change in normal range of homeostasis in response to internal environment. e.g. increased blood flow and red blood cell productionAcclimatization is not adaptation – acclimatization is temporary; adaptation is natural selection working on a population over several generations.Homeostatic process for thermoregulation: Essential to maintain internal temperatures within “tolerable” range.Enzymes have narrow optimal temperature range. 10oC change in temperature reduces enzyme activity 2 to 3 foldProteins start to denature and loose activityEndothermy: warm themselves by heat generated by metabolism (birds and mammals). Have ways of warming and cooling their bodies. Consume more food than ectothermsEctothermy: gain their heat from external sources (amphibians, lizards, snakes, turtles, fishes). Mostly change body temperature by behavior.Endotherms may have some ectothermic behavior. Two strategies are not mutually exclusive.Poikilotherm: Animal whose temperature varies with environmentHomeotherm: Has a relatively constant body temperatureCommon misconception: poikilotherms are coldblooded; homeotherms are warmblooded.Balancing heat loss and gain: Heat exchange is regulated by four physical processes:ConductionConvectionRadiationEvaporationThermoregulatory organ: major role played by the integumentary system (skin, hair, nails, fur, scales, claws)Theromregulatory adaptations:InsulationCirculatory adaptationsEvaporative loss of heatBehavioral adaptationsAdjusting thermogenesisTheromregulatory adaptations:InsulationCirculatory adaptationsEvaporative loss of heatBehavioral adaptationsAdjusting thermogenesisInsulation: Prevent flow of heat between animal and environmentHair, feather: traps air and insulates, raising hair traps more airGoose bumpsSome animals ooze oil into their hair to prevent them from getting wetTheromregulatory adaptations:InsulationCirculatory adaptationsEvaporative loss of heatBehavioral adaptationsAdjusting thermogenesisCirculatory adaptations: Regulate blood flow near body surface and maintain core body temperatureVasodialation: nerve signals relax muscles of the superficial blood vessel walls, increased blood flow to the surface, heat directed to the skin, increase in surface temperature, heat dissipated by radiation, example: jack rabbits earsVasoconstriction: Diameter of superficial blood vessels decrease, reduces blood flow to the surface and prevents heat loss.Circulatory adaptations contd….Countercurrent exchange: arrangement of tissues and blood vessels in a particular way that maximizes heat exchange. Example: goose and dolphin;VeinArterySkinCapillarynetwork withinmuscleBloodvesselsin gillsHeartArtery andvein underthe skinDorsal aortaGreat white shark…..also helps maintain core body temperature in essential tissues, like flight musclesBluefin tunaBody cavity31°29°25°27°23°21°Theromregulatory adaptations:InsulationCirculatory adaptationsEvaporative loss of heatBehavioral adaptationsAdjusting thermogenesisEvaporative heat loss: Water evaporates considerable heat during evaporationPanting in dogsSweatingFluttering of pouch at the base of the mouthTheromregulatory adaptations:InsulationCirculatory adaptationsEvaporative loss of heatBehavioral adaptationsAdjusting thermogenesisBehavioral responses:MigrationBody orientationHibernationBathingHuddlingStoring high calorie food (honey)Theromregulatory adaptations:InsulationCirculatory adaptationsEvaporative loss of heatBehavioral adaptationsAdjusting thermogenesisAdjusting thermogenesis:Shivering thermogenesis: heat production as a result of increased muscle activityNonshivering thermogenesis: some specialized chemical reactions results in heat production instead of ATP in mitochondriaAdjusting thermogenesis contd…Some ecothermic animals can do some endothermic regulation (egg incubation by Burmese python, resulting from spasmodic muscle contraction)Adjusting thermogenesis contd…Some insects perform “warm-up” preflight shivering to get critical muscles warmed upAcclimatization in Thermoregulation:Thicker coat during winterEnzymes with different optimal temperatures but same function Cells with antifreeze compoundsPhysiological thermostats – temperature regulation in humans:Fever: increase in set point of body temperature in the hypothalamus, for instance – response to