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The evolution of hormones and the nervous system

Hormones and two examples of hormonal communication

Multicellular organisms need a way for their cells [cell: Basic unit of life. Unicellular organisms only have one cell. Multicellular organisms have many cells. ] to communicate with each other. This has led to the development of hormonal communication systems.

Hormones are:

  • chemicals
  • secreted by glands
  • transported by the bloodstream to target organs

Move your mouse over the different glands in the diagram below, to see different examples of these glands.

You will need to recall two examples of the above glands and hormones for your examination. Hormones regulate the functions of many cells and organs. Compared with the nervous system, they bring about slower, but long-lasting, responses.

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