ANP 1106 Chapter Notes - Chapter 12 & 13: Upper Motor Neuron, Cranial Nerve Nucleus, Anterior Grey Column

• School: University of Ottawa
• Department: Anatomy and Physiology
• Course: ANP 1106
• Professor: Jackie Carnegie

Document Summary

Descending motor pathways deliver efferent impulses from the brain to the spinal cord divided into two groups: direct pathways (pyramidal tracts), and indirect pathways (all others); involve upper and ower motor neurons. Upper motor neuron are pyramidal cells of the motor cortex. Lower motor neuron are ventral horn motor neurons (spinal motor neuron or a cranial nerve motor neuron) that directly innervate skeletal muscles. Direct (pyramidal) pathways: originate from pyramidal neurons in precentral gyri. Impulses sent through the corticospinal tracts and synapse directly with the anterior horn of spinal cord. Stimulation of anterior horn neurons activates skeletal muscles that they are associated with. Regulates fast and fine (skilled) movements (i. e writing, needlework) Parts of the direct pathway corticobulbar tracts innervate cranial nerve nuclei. 90% are in the lateral corticospinal pathway; 10% are in the anterior corticospinal pathway (bilateral innervation of midline muscles) Indirect system: includes brain stem motor nuclei, and all motor pathways that aren"t part of pyramidal system.