The nerveous system and sense organs

• Nervous system

  A network of nerve cells and fibres that carry impulses between different parts of the body
• Nervous system

  • Gathers information about the body environment
  • Essential in movement and controlling body temperature
• Parts of the nervous system

  • Central nervous system (CNS)
  • Peripheral nervous system (PNS)
• Central nervous system (CNS)

  Comprises of brain and spinal cord, the main control centre of the body
• Peripheral nervous system (PNS)

  Consists of complex network for nerves that extends the CNS to all parts of the body
• Any damage in the CNS will impair the ability of the body to function and might be fatal
• The skull protects the brain and the vertebrae column protects the spinal cord
• Components of the PNS

  • Receptors
  • Effectors
• Receptors

  In the sense organs (eyes, ear, etc), their role is to gather information often as a result of a change in the environment (a stimulus)
• Nervous system response to stimulus

  1. Receptors send messages to the CNS along sensory nerves

  2. CNS makes decisions about how to respond

  3. CNS sends messages to effectors along motor nerves

  4. Effectors (muscles or glands) bring about the responses
• Sense organs

  • Ears (sound, balance)
  • Nose (chemicals)
  • Eyes (light)
  • Skin (touch, pressure, pain, temperature)
  • Tongue (chemicals)
• Eyes

  Light sensitive cells in the retina detect light and send messages to the brain via the optic nerve
• Ears


  Detect sounds as vibrations that pass through the air, magnified by the ear and messages carried to the brain by the auditory nerve
• Nose

  Cells inside the nose detect different chemicals, information sent to the brain along the olfactory nerve
• Tongue

  Detects chemicals in foods and passes information to the brain
• Skin

  Contains receptors that detect touch, temperature, pressure and pain, all information passed to the brain, fingertips more sensitive