The Nervous System

• Nervous System


  Consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves that carry information to/from the CNS)
• Neurone


  A nerve cell
• Sensory neurone

  A neurone that carries information from a receptor to the CNS
• Receptor


  An organ that detects a stimulus (e.g. skin, eyes, ears, nose, tongue)
• Stimulus


  A change in the environment that can be detected (e.g. pain, light, sound)
• Relay neurone

  A neurone that transmits an impulse from a sensory to a motor neurone
• Motor neurone

  A neurone that carries information from the CNS to an effector
• Effector


  A structure (muscle or gland) that carries out an action when stimulated by a motor neurone
• Coordinator


  Detects the signal from a receptor and sends a signal to the effector
• Response


  The action carried out by the effector
• Information is brought to the CNS and taken away by nerves which are bundles of neurones
• Neurones are long cells which carry electrical signals along their length
• Synapse


  The tiny gap between two neurones where the signal passes chemically across
• How information flows from receptors to effectors

  1. Stimulus

  2. Receptor

  3. Sensory neurone

  4. Relay neurone

  5. Motor neurone

  6. Effector

  7. Response
• Reflex action


  A fast, automatic and protective (FAP) response to a stimulus, often not involving the brain
• Reflex arc

  1. Stimulus

  2. Receptor

  3. Sensory neurone

  4. Relay neurone

  5. Motor neurone

  6. Effector
• The eye

  • Cornea refracts light
  • Iris controls amount of light entering
  • Lens focuses light onto retina
  • Retina contains light receptor cells
  • Optic nerve carries impulses to brain
• In bright light


  Pupil contracts, less light enters eye
• In dim light


  Pupil dilates, more light enters eye