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Medical Definition of Extrapyramidal motor system
1. Literally: all of the brain structures affecting bodily (somatic) movement, excluding the motor neurons, the motor cortex, and the pyramidal (corticobulbar and corticospinal) tract. Despite its very wide literal connotation, the term is commonly used to denote in particular the striate body (basal ganglia), its associated structures (substantia nigra; subthalamic nucleus), and its descending connections with the midbrain. (05 Mar 2000)