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Sensory and the motor neurons are the two important types of neurons that are a significant part of the nervous system. These neurons mainly work as the cells of the human body. Therefore, they are also called nerve cells. Both the sensory and the motor neurons play a significant role in the functioning of the human body. The main function associated with the sensory and the motor neurons is their transmit of the electrical signals to and from the brain. The transmission of messages across the senses and organs of the body takes place with the help of the sensory and the motor neuron accompanied by the relay neuron. In this article, we will discuss the structure, functions, and differences between the sensory and the motor neurons.
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Key Takeaways: Dorsal ganglia, spinal cord, motor, nucleus, receptors, nervous system, Central nervous system, brain, axons, neurons, nerve cells, dendrites, soma
What are Sensory Neurons?
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The sensory neurons are known to be located in the dorsal ganglia of the spinal cord. These are the afferent neuron that helps in analyzing the stimulus which is received by the sensory organs. This stimulus further activates the sensory neuron for processing and transmitting the information. These sensory neurons are concerned with traversing the sensory inputs from the receptors to the brain through the spinal cord. Mechanoreceptors, Thermoreceptors, Nociceptors, Electromagnetic receptors, and Chemoreceptors are the five different components or cells present in a sensory neuron.
Sensory Neurons
Structure of Sensory Neurons
Sensory neurons are known as afferent neurons. They are mainly located in the dorsal root ganglion. This ganglion along with the neurons is collectively situated at the dorsal roots of the spinal cord in the Central Nervous System.
- Unlike the motor neurons, sensory neurons do not carry distinct axons and dendrites. Therefore, they are called pseudo unipolar neurons.
- One common structural feature between the sensory and the motor neuron is seen in terms of both carrying the soma as their component. This soma includes its nucleus.
- A synaptic junction also serves to be an important component between the two different sensory neurons. These extend as the central branch from the soma.
- However, they are known for working as per the available receptors. These receptors are almost associated with the sensory neurons to transmit the information which is further led to the brain.
Structure of Neurons
Also Check: Electrical and Chemical Synapse
Functions of Sensory Neurons
Sensory neurons mainly function as a transmitter of information from the peripheral systems including muscles and organs back to the Central Nervous System.
- It helps in controlling the heartbeat and simultaneously maintains the blood circulation with the support of the sensory receptors instilled in the blood vessels.
- These are also responsible for the sensations of burning or tingling due to the inflammation in the sensory neurons.
- The taste buds in our tongue are able to recognize different tastes with the help of the receptors present on them accompanied by the sensory neurons for transmitting the signals to the brain.
What are Motor Neurons?
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Motor neurons are a part of the spinal cord in the Nervous system in general. All the kinds of muscle movements in a human body are linked with the functioning of the motor neurons. It is responsible for carrying away the electrical and chemical signals from the Central Nervous System (CNS) towards the muscles, thus, triggering the movement. Human beings eat, drink, blink, dance, walk, sit, and this is all because of the functioning of the motor neurons which instigates both the voluntary and the non – voluntary movements of the human muscles. Lower motor neurons and the upper motor neurons are its two types.
Motor Neurons
Also Check: Types of Reflexes
Structure of Motor Neurons
The structure of the motor neuron can be understood via its components, that is, the axons, dendrites, and the soma. These neurons carry numerous dendrites and a single axon that performs most of its functions.
- The motor neurons are known as efferent neurons and are situated in the Central Nervous System (CNS). Specifically, the motor neurons constitute the part of the motor cortex, brainstem, and spinal cord.
- The soma constitutes to be the most important part of the CNS and is situated along with the neurons in the Central Nervous System itself. Soma is also known to contain the nucleus in its cell body.
- The dendrites are another significant component of the motor neuron that looks like branch-like structures. They are known to be located at the ends of the neurons.
- From the soma, comes out an axon. It is believed to establish the link with the dendrites at the end of the neurons. They appear to have a long extension-like structure.
Functions of Motor Neurons
Motor neurons mainly function as a transmitter of information from the Central Nervous System to that of the peripheral systems including muscles and organs. However, this transmission involves multiple significant elements within it.
- Soma which is present in the motor neurons functions to control the cells through its nucleus.
- It contributes to releasing the protein for maintaining the proper functioning involving the transmission of the signals.
- Motor neurons are the ones which are responsible for controlling all the muscular movements throughout the human body.
- Motor neurons also consist of dendrites which help in sending and receiving the information from the end of neurons to another associated neuron.
- However, the internal transmission of information within the CNS is done with the help of axons. Axons are responsible for sending the information to the dendrites and vice – versa.
Check Important Notes for Spinal Cord Diagram
Difference Between Sensory and Motor Neurons
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The differences between Sensory and. Motor Neurons are as given below:
| Parameters | Sensory Neurons | Motor Neurons |
|---|---|---|
| Meaning | Cells functioning inside a body. | Cells cause the body to function. |
| Location | Dorsal Ganglion of Spinal Cord | Spinal Cord connecting with the Nervous System |
| Commands | Makes the body recognize stimulus through the receptors, helps the sense organs in responding. | Causes the movement in the muscles by commanding the cells to function |
| Function | Gets activated due to the receptors and function in sending signals to the brain. | Makes the muscle move by sending the signals from CNS to muscles or organs. |
| Components | Has dendrites and a single and short axon, thus, unipolar. | Has multiple dendrites and longer axons, thus, multipolar. |
| Controls | It controls the senses. | It controls voluntary and involuntary movements. |
| Way of Transmission | From Body organs to the Brain. | From Central Nervous System to the body organs. |
Sensory Neuron vs Motor Neuron
Things to Remember
- All the types of neurons serve as an essential unit of functioning in the human body. However, they lack the tendency of regenerating or reproducing once they die.
- Axons and Dendrites are the two most important components of a neuron through which the electrical or chemical signals are transmitted to the brain and the other cells of a body.
- Humans are known to have more than a hundred billion neurons in their brains.
- Scientists across the world are researching the technique of neurogenesis for the creation of nerve cells after birth.
- Parkinson’s and Alzheimer’s are the two most common neurodegenerative diseases and scientists are working consistently to generate the proper links between neurogenesis and neurodegenerative diseases to discover the easier way of treating them.
Read Also: Human Brain Diagram with Detailed Explanation
Sample Questions
Ques. Explain the two types of motor neurons. (3 marks)
Ans. The motor neurons are of two types, the upper motor neuron, and the lower motor neuron. The upper motor neuron can be found in the motor cortex or the brainstem. They are mainly associated with the transmission of the signals which are responsible for the voluntary movement in a body. Thus, conscious actions are performed by the upper motor neuron.
Whereas, the lower motor neurons are found in the spinal cord and are directly linked to the body organs and muscles, facilitating their movements. They are known to receive the information from the upper motor neuron for further stimulation of the actions. somatic, special visceral efferent, and general visceral motor neurons are the few subtypes of lower motor neurons.
Ques. How do relay neurons function? Does it accompany the sensory and the motor neuron in their functioning? Explain (5 marks)
Ans. The relay neuron is also known as the interneuron. Relay neuron works alongside the sensory and the motor neuron, its main function is to create the interlinking between these two main nerve cells. These neurons have extremely short axons which make them easily recognizable and simultaneously, it accompanies various other neurons to connect with the brain and the spinal cord. Mainly, the relay neuron acts as a communication link between the sensory neuron and the motor neuron.
Yes, it accompanies the motor and the sensory neurons in their functioning. For instance,
- Sensory neurons are used to transmit messages from the organs of the body to that of the brain.
- This transmission either takes place via the electrical synapse or the chemical synapse.
- As a result, the electrical synapse is responsible for transmitting the electrical signals which is a converted form of chemical signals.
- On the other hand, the chemical synapse can transmit the chemical signals directly.
- This transmission through synapse from one neuron to another is accompanied by the relay neuron.
- The same process takes place in terms of the motor neurons. Therefore, the work of the sensory and the motor neuron couldn’t be completed without the relay or the interneurons.
Ques. What is the difference between voluntary and involuntary actions? Give an example of each. (3 marks)
Ans. Every organism, be it a human or animal, performs some kind of voluntary or involuntary action. All the actions or movements which require the process of thinking before occurring is known as voluntary action. The actions which the animals regulate themselves are termed voluntary. For example, running, walking, sitting, etc.
On the other hand, the actions, about which humans are not consciously aware, are known as involuntary. All the movements and actions which are not regulated by the animals come in this category. These movements take place within the human body unconsciously, however, most of them play significant functions and remain important. For example, blood circulation, respiration, digestion, etc.
Ques. What are the similarities between the sensory and the motor neurons? (4 marks)
Ans. There are multiple similarities in the sensory neuron and the motor neuron, such as,
- Both are the types of cells that comprise components like axons and dendrites, which help them in their functioning.
- Both the neurons are responsible for transmitting the electrical signals to and from the brain and the body organs and muscles. However, their exact functioning differs in a variety of ways.
- Both the neurons require the relay neuron or the interneuron for completing their functions in a coherent way.
- The very basic similarities between both are that both the neurons function as a cell of a body. They consist of a cell body and a nucleus, all the basic functions of the human body including the cordial working of the brain, CNS, and the body organs are performed by the motor and the sensory neurons.
Ques. What are the sensory receptors? (2 marks)
Ans. Sensory receptors are the most important part of the sensory neurons, in fact, the sensory receptors serve as the basis on which the sensory neurons function. These receptors are mainly the nerve ending which is responsible for sending the signals to Central Nervous System. However, these receptors get activated only after they recognize the stimulus from the environment acting upon the body. Chemoreceptors and thermoreceptors are two types.
Ques. What are Neurons? (2 marks)
Ans. Neurons are the nerve cells that act as the messenger. These are responsible for the transmission of information across the human body. The information in the form of electrical and chemical impulses is transmitted from the organs and muscles to the brain and from the Central Nervous System to the organs. Therefore, the neurons are known to be the basic element that is responsible for the functioning of the human body. Dendrites, axons, and the cell body are the three main components of a neuron.
Ques. What is the brain of cells? Explain in the context of neurons. (2 marks)
Ans. The brain of a cell is a nucleus that is responsible for regulating all the functions of any cell. For instance, the soma which is a component of the sensory and the motor neuron consists of a nucleus that controls all its activities. The functioning of the neurons is maintained by the soma and the soma works on the basis of its nucleus.
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