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Homeostasis

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Homeostasis Homeostasis Presentation Transcript

  • Homeostasis
  • Regulating vs Conforming
    • Difference between regulating and conforming
    • Why is regulation more energy expensive than conforming?
    • Adaptation needs to outweigh the needs of the body more than the benefits of the body
  • Balances
    • The natural environment is a system of balances
      • Law of thermodynamics
    • Input and output should be equal
      • When will there be an imbalance?
  • Thermoregulation
    • Temperature affects a lot of things
    • Proteins
    • Membranes
    • What else?
  • Four physical processes of heat gain and loss
    • Conduction
    • Convection
    • Radiation
    • Evaporation
    • What is a wind chill effect?
  • Endothermy vs Ectothermy
    • Define endotherm/ ectotherm
    • True or false: ectotherms are always cold-blooded.
  • Advantages of endothermy
    • Longer vigorous activities than ectotherms
    • Sustained activity is only possible in endotherms
    • Thermal problems living in a terrestrial environment is resolved through endothermy; e.g. endotherms can live in below-freezing production- temperature that deactivate the metabolism of ectotherms
  • Disadvantage of endothermy
    • Thermoregulators invest more energy in their activity than conformers, thus, increasing the energy intake of regulators.
    • Question: why is ectothermy a good strategy in living in a new environment?
  • Adaptation of animals that thermoregulate
    • Adjusting the rate of heat exchange between the animal and its surroundings
    • e.g. insulation such as feathers, fat
    • changes in the circulatory system- vasodilation/vasoconstriction
    • countercurrent heat exchange- arteries are in opposite direction that of veins in the extremities; heat exchange is determined by physiology or environment
    • Cooling through evaporative heat loss
    • Behavioural response- posture or movement (migration/hibernation/estivation/winter sleep)
    • Changing the rate of metabolic heat- applies only to endotherms
  • Mechanisms of temperature control
    • Mammals/ birds
      • Constant heat loss
      • Constant heat production
      • Nonshivering thermogenesis vs shivering thermogenesis
  • Nonshivering thermogenesis (NST)
    • Hormones- inc metabolic activity of mitochondria rather than production of ATP
    • Brown fat
    • Insulation
    • Blubber
  • Panting and evaporative cooling
    • Increase rate of heat exchange
  • How does fur/hair help in insulation?
  • Amphibians and Birds
    • Movement is key to heat production
    • Production of mucus to counter evaporative cooling
    • Reptiles have scales that inc skin’s SA
    • Vasoconstriction in extremities of marine iguana
  • FIshes
    • Mostly are conformers
    • Endothermic fishes use countercurrent heat exchange system
    • Presence of special heat generating organs
  • Invertebrates
    • Aquatic invertebrates- mainly thermoconformers
    • Terrestrial invertebrates- same as vertebrate ectotherms
    • Flying insects- smallest endotherms
  • Flying insects
    • Generate heat through flight muscles
    • Countercurrent exchange mechanisms
      • Shutdown mechanisms during hot weather
    • Uses shivering in incubation
    • Huddling
    • Evaporative cooling
    • fanning
  • Thermostat
    • Controls temperature
    • Warm receptors- indicate inc in temp
    • Cold receptors- indicate dec in temp
    • What kind of mechanisms will each receptor activate?
    • Below normal range?
    • Above normal range?
  • Acclimation vs acclimatization
    • Acclimation- laboratory
    • Acclimatization- natural environment
    • Antifreeze- used by ectotherms in sub-zero environment
    • Proteins- e.g. Heat shock proteins
  • Torpor
    • Physiological state of low activity and low metabolism
    • Hibernation vs winter sleep
    • Estivation
    • Daily torpor
  • Osmoregulation
    • Functions in maintaining the composition of the cell’s cytoplasm
    • Mostly done indirectly
    • Open circulatory- uses hemolymph
    • Close circulatory- use interstitial fluid
    • Kidneys are specialized organs in maintaining the composition of the body’s fluid composition
  • Transport epithelia
    • e.g. transport epithelium face the outside environment to release unwanted solutes but have tight junction in between cells to inhibit back flow; functions like the Casparian strip of plants
  • Ammonia
    • Most common in aquatic animals
    • Can easily pass through membranes via diffusion
    • Invertebrates release ammonia all throughout the body
    • Fish release ammonia in the form of ammonium ions through the gills (kidneys excrete only minimal amount)
    • Freshwater fishes excrete NH4 ions but also take in Na ions through the gill epithelium to have a higher concentration of Na ions compared to the environment
  • Urea
    • less toxic compared to ammonia
    • Need less water in eliminating
    • Used by mammals, adult amphibians, marine fishes and turtles
    • Ammonia+CO2
    • Transported via the circulatory system and filtered in the kidneys
    • Can be transported in high concentration due to low toxicity
    • Uses more energy
    • Animal adaptation: amphibians in water excrete ammonia but excrete urea in land, what is the advantage of this lifestyle?
  • Uric Acid
    • relatively nontoxic nitrogenous waste
    • Insoluble in water and excreted as semisolid paste
    • Advantage: low water loss
    • Disadvantage: highly expensive
    • Present in land snails, insects, birds, reptiles
  • Osmoconformers vs osmoregulators
    • Osmoconformers- animals that have the same concentration of body fluid and of the external environment; live in relatively stable environment
    • Osmoregulators- maintains the concentration of body fluid; body fluid is not isoosmotic with that of the environment
    • Stenohaline- animals that cannot tolerate broad change in solute concentration
    • Euryhaline- animals that can tolerate substantial change in external osmolarity, e.g. salmon
  •