Reflex arc

• • Sensory neurons, intermediate relay neurons and motor neurons work together to bring about a response to a stimulus 
  • A reflex arc is a pathway along which impulses are transmitted from receptor to an effector without involving conscious regions of the brain 
  • As it does not involve the brain, a reflex response is quicker than any other type of nervous response 
• • Examples: 
  • Removing the hand rapidly from a sharp or hot object 
  • Blinking 
  • Focusing the eye on an object 
  • Controlling how much light enters the eyes 
• In the example below: 

  • A pin (stimuli) is detected by a pain receptor in the skin 
  • Sensory neuron sends electrical impulses to the spinal cord (coordinator) 
  • Electrical impulse are passed on to an intermediate neuron in the spinal cord 
  • Intermediate neuron connects to the motor neuron and passes the impulse on 
  • The motor neuron carries the impulses to the muscle in the leg (effector) 
  • Impulse causes the muscle (quads) to contract and pull leg up and away from sharp object (response) 

  
• Reflex arc pathway