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A motor neuron (or motoneuron or efferent neuron [1]) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. [2]
Any upper motor neuron lesion, also known as pyramidal insufficiency, occurs in the neural pathway above the anterior horn of the spinal cord.Such lesions can arise as a result of stroke, multiple sclerosis, spinal cord injury or other acquired brain injury.
A neural pathway connects one part of the nervous system to another using bundles of axons called tracts. The optic tract that extends from the optic nerve is an example of a neural pathway because it connects the eye to the brain; additional pathways within the brain connect to the visual cortex.
Unlike ALS, which affects both upper and lower motor neuron pathways, MMN involves only the lower motor neuron pathway, specifically, the peripheral nerves emanating from the lower motor neurons. Definitive diagnosis is often difficult, and many MMN patients labor for months or years under an ALS diagnosis before finally getting a determination ...
They typically consist of an upper motor neuron and a lower motor neuron. The lateral corticospinal tract is a descending motor pathway that begins in the cerebral cortex, decussates in the pyramids of the lower medulla [ 1 ] (also known as the medulla oblongata or the cervicomedullary junction, which is the most posterior division of the brain ...
The corticospinal tract is a white matter motor pathway starting at the cerebral cortex that terminates on lower motor neurons and interneurons in the spinal cord, controlling movements of the limbs and trunk. [1] There are more than one million neurons in the corticospinal tract, and they become myelinated usually in the first two years of life.
These tracts are in turn modulated by various parts of the central nervous system, including the nigrostriatal pathway, the basal ganglia, the cerebellum, the vestibular nuclei, and different sensory areas of the cerebral cortex. All of these regulatory components can be considered part of the extrapyramidal system, in that they modulate motor ...
Glutamate released from the upper motor neurons triggers depolarization in the lower motor neurons in the anterior grey column, which in turn causes an action potential to propagate the length of the axon to the neuromuscular junction where acetylcholine is released to carry the signal across the synaptic cleft to the postsynaptic receptors of the muscle cell membrane, signaling the muscle to ...