Hormonal System

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  • Hormonal System
    • Sends information as chemical signals
    • Made up of endocrine glands and hormones
      • Endocrine glands
        • Group of cells specialised to secrete hormones
          • E.G. Pancreas secretes insulin
      • Hormones
        • Chemical messengers
          • E.G. Proteins or peptides or steroids
        • Secreted when an endocrine gland is stimulated
          • By a change in concentration of a specific substance or by electrical impulses
        • Diffuse directly into the blood and transported by circulatory system
          • Only bind to specific receptors for that hormone
            • Known as target cells
    • Hormone = first messenger
      • It carries the chemical message from endocrine gland to receptor on target cells
        • Enzyme catalyses production of the signalling molecule in the cell
          • The signalling molecule signals to other parts of the cell to change
            • Second messengers activate a cascade (chain of reactions) in the cell
  • Exocrine glands secrete chemicals through ducts into cavities or onto surface of body
    • Usually enzymes


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