Edexcel IGCSE Biology: Double Science 复习笔记 2.10.11 The Endocrine System

Edexcel IGCSE Biology: Double Science 复习笔记 2.10.11 The Endocrine System

The Endocrine System


  • Information is sent through the endocrine (hormonal) system as chemical substances known as hormones
  • Hormones are carried by the blood and can therefore circulate around the whole body
  • Hormones transmit information from one part of the organism to another and bring about a change (they provide a signal that triggers a response)
  • They alter the activity of one or more specific target organs
  • Hormones are used to control functions that do not need instant responses
    • Compared to the nervous system the effects of hormones are slower but they act for longer


  • Hormones are produced by endocrine glands
  • The endocrine glands that produce hormones in animals are known collectively as the endocrine system
    • A gland is a group of cells that produces and releases one or more substances (a process known as secretion)




Structures that make up the endocrine system

  • Important structures in the endocrine system are:
    • Pituitary gland: a ‘master gland’ that makes hormones such as FSH and LH
    • Thyroid: produces thyroxine, which controls metabolic rates and affects growth
    • Pancreas: produces insulin, which regulates blood glucose levels
    • Adrenal glands: produces adrenaline
    • Testes (males): produce testosterone
    • Ovaries (females): produce oestrogen





The major endocrine glands of the body. These glands secrete hormones that circulate around the body in the bloodstream



Exam Tip

Make sure you can recognise and recall all the structures shown in the diagram above. Although you will not be expected to recall the thyroid gland and the role of thyroxine in the body, this endocrine gland may be referred to in an exam question that asks more generally about the endocrine system or hormones, so it is worth being aware of!