Upper Motor Neurons Lie Completely in the Central Nervous System and Control Lower Motor Neurons

Upper motor neurons are the neurons of the CNS that influence the lower motor neurons. They are typically considered the neurons of origin of the corticospinal (cerebral cortex to spinal cord), Corticobulbar (cerebral cortex to brainstem), and brain­stem motor (brainstem to spinal cord; also called bulbospinal) pathways (see Chapter 10). Upper motor neurons send axons down to the spinal cord or into the brainstem to control the lower motor neurons (see Figure 9-1).