Direct/indirect pathways, modification of descending commands

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Health + Exercise Science
HES 319
Brian Tracy

17 February Man with missing arm Doctors redirected the nerves that would normally go from the spine down the patient’s arm to the patient’s chest muscles. When the patient thinks about a specific movement of the arm or hand, the nerve impulses travel from the brain to a corresponding location on the muscle. Electrodes – fixed to the harness worn on the shoulder – direct electrical impulses emitted from the nerves and forward them to the arm. A computer processes the electrical impulses and makes the arm perform certain movements, such as flexing the elbow, opening and closing the hand, and extending the elbow and wrist. Different descending systems are very different Some pathways are direct – single neuron going to motor neurons Some synapse in brainstem before reaching motor neurons – indirect pathways Usually more medial in spinal cord Innervate more proximal muscles, more gross movements Less sophisticated (less evolved) People who are brain dead and move – spontaneous activity in brainstem Modification of descending commands Auxiliary processing centers, help motor cortex by refining motor commands Cerebellum (little brain) Adjusts the output of major descendin
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