PHGY 209 Final: CNS Motor study guide
18 Jun 2016
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Extension: flexor muscle relaxes = antagonist, extensor muscle contracts = agonist, increase angle around joint. Flexion: flexor muscle contracts = antagonist, extensor muscle relaxes = agonist, decrease angle around joint. Coordinated flexor and extensor muscle activation and relaxation (inhibiting motor neurons that innervate a muscle) Limb position is maintained by a balance of flexor and extensor muscle tension. Cell bodies in ventral horn of spinal cord or brainstem (cranial nerves) Sensory impulses move through dorsal root ganglion, into spine and up dorsal columns. Some also enter the dorsal horn of gray matter and act on interneurons. Those innervate motor neurons in ventral horn, which extend out to ventral root and innervate skeletal muscle. Descending motor commands act on theses interneurons. Activated by: skin receptor: pain, joint receptor: proprioceptive feedback, descending pathways: voluntary movements, other spinal levels: coordinates complex movements. Inhibited by: tendon receptor: tension monitoring, muscle receptor (antagonistic muscle): length monitoring.
