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  • Created by: Sophie
  • Created on: 27-04-13 10:36
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  • Homeostasis
    • The maintenance of a constant internal environment
    • Controlled:
      • Body temperature
      • Water Content- otherwise too much water could move in or out of cells and damage them
      • Ion content- otherwise too many ions could move in or out of cells
      • Blood sugar levels
      • Waste products to remove
        • CO2, toxic in high quantities
        • Urea- made from excess amino acids
    • Body temperature
      • Enzymes have an optimum temperature, within the human body its 37 degrees celcius
        • Could lead to death if too hot or cold
      • Thermoregulatory centre in the brain which acts as 'thermostat'
        • Receptors sensitive to temperature of blood flowing through the brain
        • Receives impulses from detectors in the skin
      • TOO HOT
        • Hairs lie flat
        • Sweat produced by sweat glands
        • Blood vessels dilate so more blood flows closer to the surface, making it wasier for heat to be transferred from the blood to the environment
      • TOO COLD
        • Hairs stand up to trap an insulating layer of air
        • No sweat produced
        • Blood vessels supplying skin capillaries constrict to close off the skin's blood supply
        • Shiver- requiring respiration releasing energy to warm the body


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