Neuroanatomy, Motor Neuron

Excerpt

While the term “motor neuron” suggests a single neuron type controls movement, the motor system contains multiple classes of motor neurons (see Image. Motor Neuron). Within the category of motor neurons, upper and lower motor neurons differ in origin, synaptic targets, pathways, neurotransmitters, and lesion characteristics. Overall, motor neurons (or motoneurons) form complex, tightly regulated circuits throughout the body that enable both voluntary and involuntary movement through innervation of effector muscles and glands. Upper and lower motor neurons form a 2-neuron circuit. Upper motor neurons originate in the cerebral cortex and project to the brainstem or spinal cord, whereas lower motor neurons originate in the spinal cord and innervate muscles and glands throughout the body. Recognition of the distinctions between upper and lower motor neurons, along with the pathways each neuron type follows, is essential for diagnosing motor neuron injuries and localizing lesions accurately.