Difference Between Upper and Lower Motor Neuron

To know the difference between upper and lower motor neurons, let’s get introduced to these terms. The Central Nervous system (CNS) consists of the brain in the spinal cord and upper motor neurons are higher up in the CNS whereas lower motor neurons are located at the lower regions of the CNS. Also known as motoneuron, a motor neuron is a neuron having a cell body located in the motor cortex, spinal cord, or the brainstem, and whose axon fiber projects to the spinal cord or outside of the spinal cord (to directly/indirectly control effector organs like muscles and glands. The spinal cord is the place where communication between upper and lower motor neurons takes place.

What is Upper Motor Neuron?

Upper motor neurons (upper nerve cells) are present in the cerebral cortex and also brainstem carries information down to activate interneurons and also lower motor neurons which ultimately signal muscles to contract or relax.

What is Lower Motor Neuron?

It is the nerve cell that goes from the spinal cord to the muscle  Its cell body is in the spinal cord and its termination takes place in a skeletal muscle. 

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Let’s see the below tabular chart to know the upper motor neuron vs lower motor neuron.

Difference Between Upper and Lower Motor Neuron

Upper Motor Neuron Lesion vs Lower Motor Neuron Lesion

The difference between upper and lower motor neuron lesion is such that an upper motor neuron lesion is the lesion that occurs in the neural pathway above the anterior horn of the spinal cord or cranial nerves motor nuclei; whereas a lower motor neuron lesion affects the nerve fibers that travel from the anterior horn of the spinal cord to the associated muscle.

Upper and Lower Motor Neurons: What's the Difference?   

The upper motor neuron is the motor component of the central nervous system that transmits impulses from the brain to lower motor neuron synapses, whereas the lower motor neuron is the motor component that connects with the muscles. 

The motor part of the somatic nervous system is made up of upper and lower motor neurons. They are responsible for the voluntary movement of muscles. The motor cortex, a posterior part of the frontal lobe of the brain, initiates and coordinates voluntary muscular movements. 

Upper Motor Neuron  

The upper motor neuron is a type of motor neuron that originates in the cerebral cortex's motor region or in the brainstem. It is responsible for transmitting nerve impulses from the brain to lower motor neurons. As a result, it isn't involved in nerve impulse transmission to the muscles. A neurotransmitter called glutamate transmits nerve impulses from upper motor neurons to lower motor neurons through glutamatergic receptors.   

The corticospinal tract, corticobulbar tract, colliculospinal tract, rubrospinal tract, vestibulospinal tract, and reticulospinal tract are the six pathways of the upper motor tract. 

Lower Motor Neuron    

The lower motor neuron transmits nerve impulses from the upper motor neurons to the effector's muscles. It could come from the brainstem, the anterior grey column, anterior nerve roots, or cranial nerve nuclei of the cranial nerves. Lower motor neurons' primary function is to connect the spinal cord or brainstem to the muscles. As a result, the cranial and spinal nerves are the lower motor neurons. 

Upper and Lower Motor Neurons have Similarities too   

• The somatic nervous system includes upper and lower motor neurons.   

• They help the brain send nerve impulses to the muscles.

• They are both in charge of voluntary muscular movements. 

Definition 

Upper Motor Neuron: A motor neuron that originates in the cerebral cortex's motor region or in the brainstem. 

A motor neuron that transmits nerve impulses from the upper motor neurons to the effector muscles is known as a lower motor neuron. 

Significance 

Upper Motor Neuron: A type of motor neuron that is found near the central nervous system. 

Lower Motor Neuron: This type of neuron is found near muscles. 

Transmission  

Upper Motor Neuron: Sends nerve impulses from the brain to lower motor neuron synapses. 

Lower Motor Neuron: Sends nerve impulses from upper motor neurons to the muscles via the lower motor neuron. 

Bodies of Cells 

The upper motor neuron is larger and is found in the cortex of the brain. 

Lower Motor Neurons are small motor neurons that are found in the grey matter of the spinal cord and the brainstem. 

Based on the Classification 

Upper Motor Neuron Pathway: They travel in this direction. 

Lower Motor Neuron: They innervate a specific type of muscle fiber. 

Classification   

There are six pathways in the upper motor neuron. 

Lower Motor Neuron: Nerves of the skull and spine 

Damage Signs and Symptoms  

Increased muscle tone and hyperactive deep reflexes in the upper motor neuron 

Lower Motor Neuron: Muscle atrophy, hyperactive deep reflexes, and decreased muscle tone. 

Lesion of the Upper Motor Neuron vs. the Lower Motor Neuron,  

To put it another way, an upper motor neuron lesion occurs when damage is sustained along a nerve fiber's path to or from the spinal cord's anterior horn, whereas a lower motor neuron lesion occurs when damage is sustained along a muscle's neural pathway from the anterior horn to its associated muscle.  

Conclusion 

Motor neurons in the upper motor cortex are responsible for transmitting nerve impulses from the central nervous system to the lower motor cortex, which in turn transmits nerve impulses to the muscles. It is made up of both upper and lower motor neurons, which make up the somatic nervous system, which is in charge of controlling voluntary muscular motions. The origins and functions of upper and lower motor neurons are vastly different from each other.