Biology B2 Unit 5

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Controlling internal conditions

The internal conditions of your body have to be controlled within narrow limits to maintain a constant internal environment

You have to remove waste products:

  • Carbon dioxide:
    • Produced during cellular respiration
    • If it is not removed, it lowers the pH of cells, affecting enzymes
    • Removed by being passed into the bloodstream to be transported to the lungs to be exhaled
  • Urea:
    • Produced in the liver when excess amino acids are broken down
    • Is poisonous so if levels build up, will cause damages
    • Filtered out of the blood by kidneys then passed into the bladder to be urinated out
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Controlling body temperature

Your blood glucose concentration is monitored and controlled by your pancreas

Insuling and glucagon are the hormones involved in controlling levels

Insulin converts glucose into glycogen

Glucagon breaks down glycogen (that is stored in the liver) to glucose

In diabetes, the blood glucose levels may rise to fatally high levels because the pancreas does not secrete enough insulin. It can be treated by injections of insulin before meals

It is important that the core body temp. is maintained at 37ºC for your enzymes to work best.

Body temp. is monitored and controlled by the thermoregulatory center in the brain

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Controlling body temperature - response when too c


  • A - hair muscles pull hairs on end
  • B - Erect hairs trap insulating air
  • C - Capilleries constrict (narrow) to make less blood flow to skin (vasoconstriction)
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Controlling body temperature - response when too h


  • D - Hair muscles relax making hair go flat stopping insulating air.
  • E - sweat secreted by sweat glands. Cools skin by evapouration
  • F - capillaries dilate (widen) to allow more blood to flow to the skin to radiate heat (vasodilation)
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