1.1(10) - The Endocrine System


The Endocrine System

Charlotte Jones

Signalling by using hormones

  • Hormones are molecules released by endocrine glands directly into the blood, acting as messengers, carrying signals from the endocrine gland to a specific target tissue/cell.
  • There are two types of hormone:
    • Protein and peptide hormones and derivatives of amino acids (adrenaline/insulin/glucagon)
    • Steroid hormones (sex hormones)
  • Endocrine glands release hormones directly into the blood via blood capillaries, the picture below shows different endocrine glands in the human body.
  • Exocrine glands do not release hormones.


The Target Tissue

  • The target cells have receptors on their plasma membranes that are complementary to the specific shape of the hormone molecule.
  • Homones can therefore travel around the blood without affecting cells around it that


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