PHGY 209 Lecture Notes - Lecture 23: Withdrawal Reflex, Stretch Reflex, Motor Neuron
25 Nov 2017
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They integrate voluntary movements, tension monitoring (how much force the muscles are exerting), pain, proprioceptive feedback and they take information from other spinal nerve levels. Most spinal reflexes can be overridden by individual resist. Stretch reflex: controls muscle length: monosynaptic (primary, polysynaptic (secondary) Polysynaptic at least 2 synapses involved to the motor neuron. Excitation of motor neurons (leaving through ventral root) innervating the ipsilateral flexor. Inhibition of motor neurons innervating the ipsilateral extensor since during flexion the antagonist muscle relaxes. Other neurons cross over the midline and do the opposite action of what"s o(cid:374) the ipsilateral side. This allows the contralateral leg needs to handle the weight. Proportional to the magnitude of pain stimulus. Big pain = fast response, more withdraw. The withdraw lasts longer for a more painful stimulus. The after discharge is longer for a more painful stimulus (proportional to the magnitude of stimulus) The more painful, the more interneurons are stimulated/required.
