C_S_D 4430 Lecture Notes - Lecture 22: Acetylcholine, Cranial Nerve Nucleus, Basal Ganglia
Document Summary
The upper motor neuron (umn) communicates with a lower motor neuron (lmn) Umns originate in primary motor cortex and travel to where they synapse with their respective lmns. Lmns in turn innervate their intended specific muscle fibers. Lmns are part of the pns specifically cranial or spinal neurons. Innervates muscles of the head and neck (including those used for speech and swallowing) via cranial nerves. Umn makes synaptic contact with its respective lmn in the ventral horn of the spinal cord. This synapse occurs at level where lmn exits the spinal cord as part of a spinal nerve. Axons of lmn are bundled together to form the ventral roots of their respective spinal nerves. 90% of the umns decussate (cross midline) as they leave the skull thus, innervation via the corticospinal tract is strongly contralateral. Umn makes synaptic contact with its respective lmn in one of the cranial nerve nuclei in the brainstem.
