Reflexes

• What are Reflexes 


  Reflexes are automatic responses to certain stimuli - they can reduce the chances of being injured
• An example of a Reflex is...


  if someone shines a bright light in your eyes, your pupils automatically get smaller so that less light enters your eye - this stops them being damaged
• Where does the reflex arc go through?


  the central nervous system
• Where do the neurones in the reflex arc go?


  The neurones in the reflex arcs go through the spinal cord of through an unconscious part of the brain
• Stage 1 of the Reflex Arc 


  When a stimulus (e.g. touching a hot object) is detected by recpetors an impulse is sent along a sensory neurone to the CNS
• Stage 2 of the Reflex Arc


  In the CNS the sensory neurone passes on the message to anothe type of neurone - a relay neurone
• Stage 3 of the Reflex Arc 


  Relay Neurones relay the the impulse to a motor neurone
• Stage 4 of the Reflex Arc 


  The impulse then travles along the motor neurone to the effector
• Stage 5 of the Reflex Arc 


  the effector then completes the response (e.g. the muscle contracts and moves your hand away from a hot object)
• Block Diagram of a Reflex Arc 


  Stimulus - Receptor - Sensory Neurone - CNS (relay Neurone) - Motor Neurone - Effector - Response