B3 Life on Earth

How are our nervous systems organised?

  • The evolution of multicellular organisms has led to nervous and hormonal communication systems.
  • Sensor (receptor) cells detect stimuli and effector cells produce responses to stimuli.
  • Nervous systems are made up of nerve cells (neurones) linking receptor cells (e.g. in eyes, ears and skin) to effector cells (in muscles/glands).
  • In humans and other vertebrates the nervous system is coordinated by a central nervous system (spinal cord and brain).
  • Nervous systems use electrical impulses for fast, short-lived responses.
  • Hormones are chemicals that travel in the blood and bring about slower, longer-lasting responses.
  • You must know two examples, in humans, of nervous and of hormonal communication.
  • Nervous and hormonal communication systems are involved in maintaining a constant internal environment. This is called homeostasis.
Review 7
Review 8
Back to Index