Neurones

• Stimuli are detected by sensory receptors that send impulses along sensory neurones to the central nervous system
• Neurones are specialised cells that carry nervous impulses
• Types of neurones


  • Sensory neurones
  • Motor neurones
  • Relay neurones
• Sensory neurone


  • Carries impulses to the central nervous system
  • Axon endings pass impulses to other neurones
  • Cell body contains nucleus
• Relay neurone


  • Found only in the central nervous system
  • Dendrites collect impulses from receptor cells
  • Axon carries impulses towards cell body
• Motor neurone


  • Carries impulses from the central nervous system to effector organs
  • Electrical impulse jumps from one gap in the myelin sheath to the next, speeding up the rate of transmission
  • Axon carries the electrical impulse over long distances through the body
  • Nerve ending transmits the impulse to an effector, such as a muscle or gland
• Sensory neurones carry impulses from receptors to the central nervous system
• Synapse


  The point where two neurones meet, with a small gap between them
• Transmission of nerve impulse across a synapse

  1. Electrical nerve impulse reaches end of axon

  2. Electrical impulse causes chemical neurotransmitter to be released from vesicles into gap between neurones

  3. Neurotransmitter diffuses across the gap and fits into receptors, causing a new electrical impulse in next neurone