Homeostasis

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  • Created by: emews
  • Created on: 13-11-17 16:49
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  • Homeostasis
    • The conditions inside our body must be very carefully controlled if the body is to function effectively.
    • Homeostasisis the maintenance of a constant internal environment.
      • The nervous system and hormones are responsible for this.
    • internal conditions that are regulated:
      • One example of homeostasis is the concentration of carbon dioxide in the blood being carefully controlled
      • Body temperature is controlled to maintain the temperature at which the body’s enzymes work best, which is usually 37°C.
      • Blood sugar level is controlled to provide cells with a constant supply of glucose for respiration. It is controlled by the release and storage of glucose, which is in turn controlled by insulin.
      • Water content is controlled to protect cells by stopping too much water from entering or leaving them.
      • Water content is controlled by water loss from:
        • the lungs - when we exhale
        • the skin - by sweating
        • the body - in urine produced by the kidneys
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    • Homeostatic control is achieved using negative feedback mechanisms:
      • if the level of something rises, control systems reduce it again
      • if the level of something falls, control systems raise it again
    • Regulating body temperature
      • When we get too hot:
        • Sweat glands in the skin release more sweat. The sweat evaporates, removing heat energy from the skin.
        • Blood vessels leading to the skin capillaries become wider - they dilate - allowing more blood to flow through the skin, and more heat to be lost.
      • When we get too cold:
        • Muscles contract rapidly - we shiver. These contractions need energy from respiration, and some of this is released as heat.
        • Blood vessels leading to the skin capillaries become narrower - they constrict - letting less blood flow through the skin and conserving heat in the body.
      • The skin
        • The hairs lie flat when we are warm, and rise when we are cold.
        • The hypothalamus is the part of the brain which monitors the body's temperature.
        • The hypothalamus responds to this information by sending nerve impulses to effectors to maintain body temperature.
    • Glucose is needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level.
      • Insulin is a hormone - produced by the pancreas - that regulates glucose levels in the blood.
      • Diabetes is a condition in which the blood glucose levels remain too high.
        • It can be treated by injecting insulin.

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