reflexes

• receptor - detects stimulus and creates an action potential in the sensory neurone
• sensory neurone - carries impulse to the spinal cord
• relay neurone - connects the sensory neurone to the motor neurone within the spinal cord or the brain
• motor neurone - carries impulse to the effector to carry out the response
• Knee-jerk reflex:

  • spinal reflex
  • when the leg is tapped just below the patella, it stretches the patella tendon and acts as a stimulus
  • stimulus initiates reflex arc that causes extensor muscle on top of the thigh to contract
  • relay neurone inhibits motor neurone of the flexor muscle, causing it to relax
  • this contraction causes the leg to kick
  • maintains posture and balanec
• Blinking reflex

  • involuntary blinking of the eye lids
  • occurs when the cornea is stimulated, response to loud sounds or bright light
  • purpose is to keep the cornea safe from damage
  • stimulus triggers an impulse along the sensory neurone, impulse passes through relay neurone in the lower brain stem
  • impulse sent along branches of the motor neurone to initiate a motor response to close the eyelids
• importance of reflex arcs:

  • Involuntary - They allow the brain to concentrate on complex processes.
  • Rapid - They ensure a swift response.
  • Protective - They safeguard the body from potential injuries.
  • Innate - They are intrinsic mechanisms present from birth, eliminating the need for learning.