The ‘extrapyramidal system’ in general refers to the brain’s motor circuitry excluding the corticospinal system. It primarily refers to the basal ganglia and cerebellar circuits and connections that play an important role in modifying and maintaining coordinated conscious and unconscious movements. But because the basal ganglia and cerebellum have no direct projections to the spinal cord, ‘extrapyramidal’ must logically also include all of the descending systems of the brainstem (reticulospinal etc.) that initiate and sustain movements in the absence of the pyramidal system.
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