The sensory and motor tracts and pathways in the spinal cord carry out the conduction of sensory and motor nerve impulses to and from the brain. Somatic sensory pathways and somatic motor pathways are the two types of spinal cord tracts in the human nervous system. The somatic sensory pathways transmit sensory impulses to the cerebral cortex from somatic sensory receptors, and the somatic motor pathways transmit motor impulses to the skeletal muscles from the cerebral cortex. The upper motor neuron and lower motor neuron are the two basic sets of neurons present in the somatic motor pathways. Here in this article, let us look at the various difference between upper and lower neurons.
Upper Vs Lower Motor Neuron
|Upper Motor Neuron||Lower Motor Neuron|
|It is entirely located in the central nervous system||It is either located in the spinal cord gray matter or within the cranial nerve nuclei in the brain stem.|
|Transmits motor impulses from the brain to the synapses of the lower motor neuron||Collects the transmitted motor impulses from the upper motor neuron to the muscles in the body|
|Cell bodies of upper motor neuron bigger than lower motor neuron cell bodies||Cell bodies are comparatively smaller|
|Classified based on the pathways they travel in||Classified based on the type of muscle fibre they innervate|
|They form synapses with the lower motor neurons||They form synapses with the muscles in the body|
|Lower motor neuron lesions result in muscular atrophy, flaccid muscle weakness, fasciculation and hyporeflexia||Upper motor neuron lesions produce spastic hyperreflexia and muscle weakness|
What are Upper Motor Neurons?
The term upper motor neurons was introduced by William Gowers found in the cerebral cortex and brainstem that carries information down to activate interneurons and lower motor neurons.
What are Lower Motor Neurons?
The lower motor neuron begins in the spinal cord and ends in the skeletal muscle. If the lower motor neurons are lost, it leads to weakness, muscle twitching, and muscle atrophy.
Both upper and lower motor neurons make up the somatic nervous system that controls the voluntary muscular movements. From the differences, we can conclude that the main difference between upper and lower motor neuron is the origin and the function.
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