Science // Biology // B1 // Homeostasis

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  • Homeostasis
    • It is vital that the internal environment of the body is kept fairly constant. This is called homeostasis.
    • Different factors that need to be kept include;
      • Water
      • Temperature
      • Sugar levels
      • Mineral content
    • Many mechanisms that are used for homeostasis involve hormones.
      • Hormones are chemical messengers that are carried in the blood stream. They are released by glands and pass to their target organ. Hormones take longer to have an effect than nerves but their responses are usually longer.
        • Many of these control mechanisms work by negative feedback which means that if the levels change too much, hormone is released and this brings the change back to normal levels.
    • Homeostasis process
    • Blood sugars.
      • It is vital that the sugar or glucose level of the blood is kept constant. If it gets too low then cells will not have enough use for respiration and if it is too high, then glucose may star to pass out in the urine.
      • Insulin is the hormone that controls the level of glucose in the blood.
      • Blood Glucose levels too high?
        • 1. Insulin injected by pancreas
          • 2. Glucose absorbed by tissues
            • 3. Glucose absorbed by the liver
              • 4. Blood glucose reduced
      • Blood glucose levels too low?
        • 1. Insulin not injected by pancreas
          • 2. Less glucose absorbed by tissue
            • 3. Less glucose absorbed by liver
              • 4. Blood glucose increased
      • How diabetics control blood sugars.
  • When glucose levels are too high, more insulin is made. The insulin converts excess glucose into glycogen to be stored in the liver.
    • Insulin is the hormone that controls the level of glucose in the blood.
    • People with diabetes do not produce enough insulin, the need insulin injections in order to control the levels of glucose in their blood, they also need to control their diet carefully too.


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