Difference Between Sensory and Motor Neurons

In a nervous system, neurons are the basic functional and structural units that are present in billions. Before getting the difference between sensory and motor neurons, know that both of them function to communicate and pass electrical impulses to and from the central nervous system. Based on the functioning, there are three main types of neurons:

• Sensory Neurons
• Motor Neurons
• Inter-Neurons

We will discuss the differences between sensory and motor neurons, but first, take a glance at the comparison table below!

Comparison Table

	Sensory Neurons	Motor Neurons
Definition	Neurons transmit impulses from the external organs to the brain.	Neurons transmit impulses from the brain to the sensory organs.
Polarity	Unipolar in nature	Multipolar in nature
Location	The dorsal root of ganglion	The ventral root of ganglion
Length of Fibers	Short axons & long dendrites	Long axons & short dendrites
Number of Neurons	Average of ten million neurons in an adult	Average of ½ million neurons in an adult
Present in	Tongue, ears, eyes, skin, and nose	Glands and muscles

Sensory Neurons – Brief Description

Another name for sensory neurons is the “afferent neurons. These are the nerve cells of a body, accountable for transferring the external stimuli to the impulses inside a body. Most of the sensory neurons work as pseudo-unipolar as they have one axon to divide into two branches. All the sensory information in the brain goes along the afferent nerve fibers via the spinal cord. This information or stimuli can be from outside a body or inside. For instance, sound or light and several senses of body postures, etc.

Motor Neurons – Brief Description

A motor neuron is commonly called a “motoneuron,” which is located in the motor cortex, spinal cord, and brainstem of a living body. These neurons appear with the usual body type for a nerve cell such that it’s multi-polar with a single axon and numerous dendrites.

All the fibers of motor neurons extend to the spinal cord or outside of it to manage the effector organs, either directly or indirectly. The central function of a motor neuron is to transmit electrical impulses from the spinal cord to smooth and skeletal muscles. This way, it controls all the muscular movements in one’s body.

Check Out the Differences Between Sensory & Motor Neurons

If you thoroughly compare these two neurons, the key difference lies in their structure and working. Sensory and motor neurons help the central nervous system in coordinating several functions of a body.

Main Function

Sensory Neurons

Its fundamental purpose is to notice and transmit the external impulses to the internal, electrical stimuli that will receive a further message from the brain.

Motor Neurons

Motor neuron promotes the contraction of muscles and also adjusts proprioceptive sensitivity. So, it works to handle all the muscular movements in a body.

Direction of Impulses

Sensory Neurons

These neurons are responsible for drawing external impulses from the organs to the CNS.

Motor Neurons

These neurons transmit motor impulses/stimuli from the CNS to the targeted effector cells.

Location of the Cell Body

Sensory Neurons

A cell body of such neurons is present in the spinal cord at the dorsal root of the ganglion. Moreover, there are no extended dendrites situated in it.

Motor Neurons

The cell body of a motor neuron is detected in the spinal cord, at the ventral root of the ganglion, and consists of extended dendrites.

Type of Pathways

There are usually two pathways for neurons in a body, mainly the efferent pathway and the afferent pathway.

Sensory Neurons

Sensory neurons follow the afferent pathway having afferent fibers, which means it carries impulses from an external organ to the brain and spinal cord.

Motor Neurons

On the other hand, motor neurons pursue the efferent pathway having efferent fibers, which means it conducts impulses away from the brain and towards the organs.

Average Neurons in an Adult

Sensory Neurons

In an adult, the average number of sensory neurons is 10 million.

Motor Neurons

In an adult, the average number of motor neurons is almost a half million.

Location of Neurons

Sensory Neurons

Sensory neurons are largely present in ears, eyes, skin, nose, tongue, etc.

Motor Neurons

Motor neurons are usually found in the glands and muscles of a body.

Polarity of Neurons

Sensory Neurons

These neurons are unipolar in nature.

Motor Neurons

These neurons are naturally multipolar.

Size of Dendrites & Axons

Sensory Neurons

These neurons consist of numerous short dendrites at both ends of a cell body, having one long axon in between.

Motor Neurons

Motor neurons have a cell body at one end and long dendrites on the other. Whereas a long axon is present in the middle.

Conclusion

From the above article, we hope to clear all the essential differences between sensory and motor neurons. There is no way that one has more importance than the other, but both hold their own significance. Either its sensory or motor neurons, both types work together to coordinate the impulses and overall working of a body.