Difference Between Upper And Lower Motor Neurons

Upper And Lower Motor Neurons The sensory and motor tracts and pathways of 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. Somatic sensory pathways transmit sensory impulses to the cerebral cortex from somatic sensory receptors, and somatic motor pathways transmit motor impulses to skeletal muscles from the cerebral cortex.

The upper motor neuron and the lower motor neuron are the two basic sets of neurons present in somatic motor pathways . Here in this article, let’s look at the various differences between upper and lower neurons.

Main differences:

Upper motor neuron Lower motor neuron
It is completely located in the central nervous system. It is found in the gray matter of the spinal cord or within the nuclei of the cranial nerves in the brain stem.
Transmits motor impulses from the brain to lower motor neuron synapses It picks up the motor impulses transmitted from the upper motor neuron to the muscles of the body.
Upper motor neuron cell bodies larger than lower motor neuron cell bodies Cell bodies are comparatively smaller
Classified according to the routes they travel Classified according to the type of muscle fiber they innervate
They form synapses with lower motor neurons. They form synapses with the muscles of the body.
Lower motor neuron injuries cause muscle atrophy, flaccid muscle weakness, fasciculation, and hyporeflexia Upper motor neuron injuries produce spastic hyperreflexia and muscle weakness

What are upper motor neurons? 

The term upper motor neurons was introduced by William Gowers which is found in the cerebral cortex and brainstem that carries information to activate interneurons and lower motor neurons.

What are lower motor neurons?

The lower motor neuron begins in the spinal cord and ends in skeletal muscle. If lower motor neurons are lost, weakness, muscle spasms, and muscle atrophy occur.

Both upper and lower motor neurons form the somatic nervous system that controls voluntary muscle movements. From the differences, we can conclude that the main difference between upper and lower motor neuron is origin and function.

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