Edexcel IGCSE Biology: Double Science 复习笔记 2.10.11 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