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Neurons basal ganglia basal ganglia suppress unwanted

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Unformatted text preview: ovement initiation. movement initiation. DESCENDING MODULATORY PATHWAYS (UPPER MOTOR NEURONS) MOTOR Upper motor neurons influence the spinal cord Upper motor neurons influence the spinal cord by two routes: by two routes: 1) direct projections to the spinal cord (ventral 1) direct projections to the spinal cord (ventral corticospinal tract; lateral corticospinal tract) corticospinal tract; lateral corticospinal tract) 2) indirect projections to brainstem centers 2) indirect projections to brainstem centers tthat in turn project to the spinal cord (e.g. hat in turn project to the spinal cord (e.g. corticoreticulospinal ttract) corticoreticulospinal tract) ract) Spinal Motor Tracts Spinal There are several pathways which innervate the alpha-motor neurons. innervate motor can be roughly grouped into the grouped into voluntary (direct projection) motion projection) motion pathways pathways lateral and anterior corticospinal corticospinal systems (pyramidal tracts) postural pathways.(extrapyramidal, pathways.(ex indirect projection) indirect pathways do not originate in cortex their function is to maintain an upright posture against gravity There are three principal pathways in humans: the vestibulospinal, vestibulospinal tectospinal, and reticulospinal tectospinal and reticulospinal pathways. rubrospinal system (from the red rubrospinal system nucleus) is also sometimes included, but in humans it may be insignificant. Pyramidal Motor System (Corticospinal Tract) controls all our voluntary movement via a two-neuron system: via neuron upper motor neurons in the primary motor cortex motor upper motor neuron axon extends all the way from the brain down to the spinal cord, a distance 1-3 feet the feet or more lower motor neurons in the anterior horn of the spinal cord. axon extends from the spinal cord to the skeletal muscles of the arms or legs, a distance 4-5 feet in very or feet tall people. Corticospinal Tract Corticospinal Upper motor neurons pass from Upper motor neurons pass from tthe motor cortex he motor cortex tthrough the internal capsule of hrough the internal ca...
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