Spinal Reflexes

Spinal Reflexes

1. Principles of Spinal Reflexes

   • adaptable to particular motor tasks
   • coordinated reflex responses in several muscles
     • Polysynaptic: Flexion
       • afferent from nociceptor, efferent motor to muscle, inhibitory interneuron to make sure antagonist muscle is inactive
     • Monosynaptic: Stretch
       • stretch receptor: muscle spindle
         • What is the structure?
           • intrafusal muscle fibers (innervated by sensory axons)
             • nuclear chain
             • nuclear bag
               • dynamic
               • static
           • gamma motor neurons
             • dynamic
             • static
           • sensory axons: innervate spindles
             • Ia: primary sensory ending
             • II: secondary sensory
         • What is its function?
           • detect changes in muscle length
       • afferent from spindle, efferent to muscle, inhibitory interneuron to make sure antagonist muscle is inactive
   • supraspinal centers modulate and adapt spinal reflexes or reverse movements