Introduction of sensory and motor neurons
The study and practice of biology helps us to analyze the human body adequately. The nervous system is a critical part of our body that needs to be understood in order to lead a prosperous life. Neurons form the basic foundation for receiving sensory inputs, instructing the muscle through motor commands, and sending the signals back to the brain to initiate actions. Talking about the types of neurons on the basis of functions and structure, the central nervous system comprises two types of neurons- Sensory and Motor Neurons. We’ll be looking at the difference between sensory and motor neurons. The difference between sensory and motor neuron has been tabulated below:
Sensory Vs Motor Neurons
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We hope that it’s pretty much clear how sensory and motor neurons differ from each other. Now, we will be looking forward to our next section i.e. difference between sensory and motor neurons on the basis of their structure.
Structural Differences: Difference Between Sensory Neuron and Motor Neuron
Although the core function of the neurons differentiate between sensory neuron and motor neuron, both the neurons also differ in structure. Let’s look into the structural difference between the sensory neuron and motor neurons and what makes them different from each other.
Sensory Vs Motor Nerves: Difference Between Sensory Neuron and Motor Neuron
To differentiate between sensory neuron and motor neuron, we will be defining the structure of both the neurons one by one.
Sensory Nerves Vs Motor Nerves
Structure of Sensory Neurons:
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Sensory neurons conduct signals from sensory organs to the CNS. Sensory Neurons arise from the dorsal root ganglion, which are specialized clusters present at the dorsal roots of the spinal cord.
Sensory neurons lack distinct axons and dendrites.
Sensory neurons possess receptors.
The soma of the sensory neurons possesses a nucleus and other cell organelles.
A synaptic junction with second-order sensory neurons is formed as the central branch extends from soma to the posterior horn of the spinal cord.
These neurons are also known as pseudo unipolar neurons.
Structure of Motor Neurons
To understand the difference between sensory neuron and motor neuron in a better way, let's learn the structure of Motor neurons.
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Motor nerves transmit the signals from the CNS to the sensory organs and thus, help in initiating actions.
These neurons are located at the ventral root ganglion of the spinal cord.
Motor neurons consist of a long axon and multiple dendrons.
They lack receptors.
These neurons are also known as multipolar neurons.
These are the main differences between sensory and motor nerves.
We hope that the functional difference between sensory nerve and motor nerve is pretty much clear. Thus, we will be moving towards our next section that is to differentiate sensory nerves and motor nerves on the basis of the functions they perform.
Differentiate Between Sensory and Motor Neurons on the Basis of Functions
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Till now, we have just discussed the basic functions and how to differentiate between sensory neuron and motor neuron. But, the functions of sensory and motor neurons are vast. Let's compare and contrast sensory and motor neurons on the basis of the function they perform in the human body.
For the difference between sensory and motor neurons, let’s first look at the functions performed by sensory neurons.
Functions of Sensory Neurons
We will see the difference between sensory and motor nerves on the basis of function.
We know, sensory neurons transmit the signal from the sense organs to the CNS in the form of sensory signals. Let’s look at some of the most important functions performed by sensory neurons in the human body.
Controlling the Heartbeat and Blood Circulation
The sensory receptors in the blood vessels are responsible for registering blood pressure. Sensory neurons can be found in the aorta, carotid arteries, pulmonary artery, capillaries in the adrenal gland, and the tissues of the heart itself, from where the signals are sent to the medulla and thus, help in controlling BP and blood circulation.
Effects in Neuritis
Inflammation of sensory neurons results in the sensation of burning, tingling, or stabbing pain. These are even worse at night and are aggravated by temperature change.
Taste Buds
Taste receptor cells on our tongues form a group of 50 to 150. These cells respond to the chemicals present in the food and thus, form taste buds, which help us in differentiating among the food items of different tastes.
Fun Fact:
An average adult can have more than 8,000 taste buds!
Sensory neurons and motor neurons work in coordination which each helps in the functioning of our body. So, if you are able to taste something, it’s because of the harmonized working of both the neurons.
We hope that the difference between sensory nerve and motor nerve is now clear. The topic is pretty much simple and just needs a bit of understanding. The difference between sensory and motor nerves can be well understood with the table in the first section.
FAQs on Difference Between Sensory and Motor Neurons
1. What are the key differences between sensory and motor neurons?
The primary difference lies in the direction of nerve impulse transmission. Sensory neurons carry signals from sensory receptors towards the central nervous system (CNS), while motor neurons carry signals away from the CNS to effector organs like muscles and glands. Key differences are:
- Direction of Impulse: Sensory neurons are afferent (carry signals to the CNS); motor neurons are efferent (carry signals away from the CNS).
- Location of Cell Body: In sensory neurons, the cell body is located in the dorsal root ganglion of the spinal cord. In motor neurons, it is located in the ventral horn of the spinal cord.
- Structure: Sensory neurons are typically pseudounipolar, having a single process that splits into two branches. Motor neurons are multipolar, with a distinct axon and multiple dendrites.
- Function: Sensory neurons detect stimuli (like touch, light, or sound) and transmit this information for processing. Motor neurons transmit commands to trigger a response, such as muscle contraction.
2. Are 'afferent' and 'efferent' neurons the same as sensory and motor neurons?
Yes, these terms directly correspond to sensory and motor neurons based on the direction they transmit information. Afferent neurons are sensory neurons because they carry nerve impulses 'arriving' at the central nervous system (CNS) from the body's periphery. Efferent neurons are motor neurons because they carry nerve impulses 'exiting' the CNS to produce an effect in the body.
3. What is the role of interneurons in relation to sensory and motor neurons?
Interneurons, also known as relay or association neurons, act as the crucial link between sensory and motor neurons. Located entirely within the central nervous system (CNS), their primary function is to process and integrate the incoming signals from sensory neurons and then transmit the appropriate command to motor neurons. They are essential for complex pathways and reflexes, allowing the brain and spinal cord to make a decision before a response is initiated.
4. How do sensory and motor neurons work together in a reflex arc?
In a reflex arc, sensory and motor neurons work in a rapid, coordinated sequence to produce an involuntary response. For example, if you touch a hot object:
- 1. A sensory receptor in your skin detects the heat (stimulus).
- 2. A sensory neuron transmits a high-speed signal from your finger to the spinal cord.
- 3. In the spinal cord, an interneuron receives the signal, processes the threat, and immediately relays it to a motor neuron.
- 4. The motor neuron carries the 'withdraw' command from the spinal cord to the muscles in your arm (the effector).
- 5. The muscles contract, pulling your hand away from the hot object. This entire pathway from stimulus to response occurs before the brain even consciously perceives the pain.
5. What are the main functions of a motor neuron?
The main function of a motor neuron is to carry instructions from the central nervous system (CNS) to the body's effectors, which are typically muscles or glands. This initiates a physical response. Key functions include stimulating muscle contraction, which allows for all voluntary movements like walking and talking, as well as involuntary actions like the beating of the heart. They also trigger glandular secretion, such as releasing hormones or enzymes.
6. What is the basic structure of a sensory neuron?
A typical sensory neuron has a unique structure known as pseudounipolar. It features a cell body (soma) located off to the side in the dorsal root ganglion, just outside the spinal cord. From this cell body, a single short process extends and splits into two longer branches: a peripheral branch that extends to the sensory receptor in the skin or organ, and a central branch that extends into the spinal cord to communicate with other neurons.
7. What happens if motor neurons are damaged, but sensory neurons remain intact?
If motor neurons are damaged while sensory neurons are unaffected, a person would still be able to feel sensations like touch, pain, pressure, and temperature in the affected area. However, they would lose the ability to voluntarily move the muscles in that region. The communication pathway from the central nervous system to the muscles is broken, resulting in paralysis, even though the sensory feedback loop to the brain remains functional.
