Difference Upper and Lower Motor Neurons

The spinal cord’s sensory and motor pathways support the transmission of sensory and motor impulses, respectively. Motor routes take impulses from the brain and spinal cord to the muscles of the effector, whereas sensory pathways take impulses from the sense receptors to the brain and spinal cord. The two fundamental sets of neurons found in the somatic motor pathways are upper and lower motor neurons. Let’s examine the different distinctions between upper and lower neurons in this post. 

Upper Motor Neurons

William Gowers coined the term “upper motor neurons” (UMNs) in 1886. They are present in the cerebral cortex and brainstem and transmit information to lower motor neurons and interneurons, which in turn activate muscles directly. The primary source of voluntary movement comes from UMNs in the cerebral cortex. The bigger pyramidal cells in the cerebral cortex are these ones. In layer V of the primary motor cortex, which is located just below the cerebral cortex’s surface, are large pyramidal cells known as Betz cells. With a diameter of over 0.1 mm, Betz cell neurons have the largest cell bodies in the brain.

Structure and Function of the Upper Motor Neurons

Upper Motor Neurons have a cell body in the cerebral cortex, basal ganglia, or brainstem, and a long axon that travels down the spinal cord to synapse with LMNs. UMNs are highly branching neurons that link to numerous other neurons in the brain and spinal cord. Upper Motor Neurons are responsible for controlling voluntary movement and maintaining muscle tone. UMNs get information from numerous brain areas, such as the primary motor cortex, premotor cortex, basal ganglia, and cerebellum, which modulate their activity to generate smooth and synchronized motions.

Significance OF  Upper Motor Neurons

A kind of motor neuron located close to the central nervous system. Damage or malfunction to the Upper Motor Neurons can cause a number of movement disorders, including spasticity, weakness, and loss of motor control. Stroke, severe brain injury, cerebral palsy, and multiple sclerosis are common diseases that damage Upper Motor Neurons. In these circumstances, it’s possible for the UMNs to sustain an injury, impairing communication between the brain and the LMNs and causing a loss of voluntary motor control.

Lower Motor Neurons

Lower motor neurons (LMNs) are motor neurons with a motor function that are either found in the brainstem’s cranial nerve nuclei and the anterior nerve roots (cranial nerve lower motor neurons) or in the anterior grey column. Spinal lower motor neurons, which innervate skeletal muscle fibers and serve as a conduit between upper motor neurons and muscles, are essential for many voluntary actions. Lower motor neurons of the cranial nerve also help with vocalization, chewing, and some voluntary movements of the tongue, face, and eyes. Atrophy of the muscles and flaccid paralysis can result from damage to the lower motor neurons.

Structure and Function of the Lower Motor Neurons

The axon of the Lower Motor Neurons ARE shorter and runs from the spinal cord or brainstem to the muscles they govern. They are in charge of activating muscles and creating movement. Lower Motor Neurons are responsible for controlling voluntary movement and maintaining muscle tone. They receive information from several sources, including the primary motor cortex, basal ganglia, and cerebellum, which modify LMN activity to create smooth and synchronized motions.

Significance OF  Lower Motor Neurons

This sort of neuron can be found close to muscles. Multiple motor diseases, including muscular weakening, atrophy, and paralysis, can be brought on by  Lower Motor Neurons injury or malfunction. Amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and polio are common diseases that impact Lower Motor Neurons. Under these circumstances, the LMNs may be harmed, resulting in a loss of muscular control and strength.

Difference Between Upper and Lower Motor Neurons

Upper Motor Neurons	Lower Motor Neurons
The central nervous system contains it totally.	Either the cranial nerve nuclei in the brain stem or the grey matter of the spinal cord contain it.
Upper motor neuron cell bodies are larger than lower motor neuron cell bodies.	Comparatively speaking, cell bodies are smaller than upper motor neurons.
According to the pathways they are using, they are categorised.	Categorized according to the kind of muscle fibres they innervate.
They connect with the lower motor neurons through synapses.	They develop synapses with the body’s muscles.
Muscle weakness and spastic hyperreflexia are symptoms of upper motor neuron lesions.	Muscular atrophy, flaccid muscle weakness, fasciculation, and hyporeflexia are the effects of lower motor neuron injuries.