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