Anatomy and Cell Biology 3319 Chapter Notes -Pontine Nuclei, Rubrospinal Tract, Skeletal Muscle

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3 main ascending pathways: spinocerebellar pathway, dorsal column pathway, spinothalamic pathway. Descending pathways: deliver motor (output) instructions from brain to spinal cord, each pathway contains, upper motor neurons. Originate in gray matter of the brain & send long axons down a descending tract of the spinal cord. Axon synapse with lower motor neurons: lower motor neurons. Axons of lower motor neurons exist ventral root of cord to innervate muscle or gland: classified as two groups: direct pathways or indirect pathways. Direct pathways (pyramidal tracts: extend without synapsing form the pyramidal cells in cerebral cortex to spinal cord, pyramidal cells are large neurons found in primary motor cortex. Long axons of pyramidal cells form pyramidal tracts (corticospinal tracts) control precise & skilled voluntary movements. In lateral corticospinal tract occurs in medulla with decussation of the pyramids: axons comes down and upper motor neuron makes direct connections to lower motor neuron.

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