The Nervous System

• Stimulus


  Anything that we respond to
• Receptors


  • In animals, receptors respond to stimuli (e.g. sound, smell, visual stimuli)
  • There are many types of receptor, each responding to a particular type of stimulus
  • If a receptor is stimulated, it may cause an effector such as a muscle or gland to produce a response
• Neurones


  Nerve cells that link the receptors to a coordinator
• Central nervous system (CNS)


  • The coordinator, consisting of the brain and spinal cord
  • The role of the CNS is to make sure the correct receptor is linked to the correct effector
  • A neurone carries information in the form of small electrical charges called nerve impulses
• The role of the nervous system in animals is summarised in Figure 6.1
• Types of nervous action


  • Voluntary actions
  • Reflex actions
• Systems that allow humans to respond to changes in the environment


  • Nervous system
  • Hormonal system
• Stimulus

  Changes in the environment that humans respond to
• Receptors


  • Receive information about changes in the environment
  • There are many types, each sensitive to a different type of stimulus
• Response to stimulus


  1. Receptor receives information

  2. Effector (e.g. muscles) produces a response
• Nerve cells or neurones link receptors and effectors to the co-ordinator (brain or spinal cord) and transport the electrical signal (nerve impulse)
• Jane texts John


  John texts Jane
• The receptors for the 5 senses are found in the ear, skin, eye, tongue, and nose