What is a Nerve Cell?

The nerve cell, also known as a neuron, is the main structural and functional unit of the nervous system. The neurons or nerve cells are primarily involved in receiving and transmitting information from and to the brain. They transfer various messages from different parts of the body to the brain and back. Neurons have a lot in common with other types of cells, but they are different from them based on their structure and functions. The human body consists of millions and billions of nerve cells. The size of nerve cells can vary from nanometers to meters. The length of nerve cells depends on their function and location in the body.

Structure of Nerve Cell

The shape, size, and structure of nerve cells depend on their position and function in the body. Usually, the size of nerve cells varies depending on how long the electrical impulses are to be transmitted.  

The nerve cell is a specialized individual cell that forms our nervous system. All the human body neurons have three parts, a cell body, an axon, and dendrites. The nerve cell parts consist of the following:

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  • Cell Body: 

The cell body in a nerve cell is its core. It is also called soma. The cell body consists of the nerve cell’s nucleus along with other specialized cell organelles such as the endoplasmic reticulum, Golgi apparatus, mitochondria and other components. The cell body is an essential part of a neuron and carries genetic information. It also helps maintain the cell’s overall structure and provides energy to carry out the cell’s activities.

  • Axon: 

An axon is a part of the nerve cell, which is a long tube-like structure that joins the cell body at a specific position. The axon is primarily involved in carrying the electrical signals from the cell body to the neuron ending and transmitting it to other surrounding neurons.

  • Dendrites: 

They are the root-like projections on a cell body that facilitate transmission and receiving of messages to and back from other neurons. Dendrites process and send the electrical impulses received from the axon endings to the cell body.

  • Myelin Sheath: 

It is the outermost layer of a nerve cell. Its primary function is to cover and protect the nerve fibres in the neurons.

  • Synapse: 

It is known as the ending part of the nerve or nerve junction. Its primary function is to permit the entry of electrical impulses from one neuron to another. 

Types of Nerve Cell or Neurons

Now that we have studied the nerve cell parts and length of nerve cells let’s look at the different types of neurons. Depending on their functions, neurons can be broadly classified into three types:

  • Sensory Neurons: 

Sensory neurons are generally found in the sense organs of the human body, such as the eyes, nose, skin, tongue and ears. These nerve cells are triggered by the chemical and physical inputs of our environment, such as sound, heat and light. The sensory neurons facilitate the movement of sensory impulses from the sensory organs to the central nervous system. There are approximately 10 millions sensory neurons in the human body. 

  • Motor Neurons: 

Motor neurons are the ones that facilitate the transmission of motor impulses from the central nervous system to the different parts of the body. These types of neurons play a major role in the voluntary and involuntary movements of the body. The motor neurons are primarily found in various glands and muscles of the human body.

  • Interneurons: 

Interneurons are those neurons that act as a mediator between sensory neurons, motor neurons and the central nervous system. They help in the smooth transmission of signals. They help in conducting a smooth communication between the neurons and the central nervous system. The interneurons are present in all parts of the body and are exclusively found in the central nervous system.

Functions of Nerve Cells

The primary function of every nerve cell present in the human body is to transmit messages. But the nerve cells are also involved in the following activities:

  • It helps the body to respond to the surrounding stimuli.

  • It helps the body in the smooth conduct of metabolic activities.

  • It helps in both the voluntary and involuntary movement of the body parts.

  • It helps establish communication between the central nervous system and the body parts by enabling the smooth transmission of messages.

FAQs (Frequently Asked Questions)

Q1: How are Sensory Neurons different from Motor Neurons?

Answer: When compared with the motor neurons, the sensory neurons have a different set of functionality. The sensory neurons carry signals or electrical impulses from the sensory organs to the central nervous system. On the other hand, the motor neuron carries electrical signals from the central nervous system to the different parts of the body, which include sensory organs. The axon of sensory neurons is short in comparison to the axon of motor neurons. Sensory neurons consist of a single long dendron, but motor neurons consist of more than one dendrons. The sensory neurons are mostly located in the sensory organs of the body. Whereas the motor neurons are located mostly in glands and muscles.

Q2: What is Myelin Sheath?

Answer: Myelin is a fatty material, which is produced by the glial cells of the neurons. The myelin wraps around the axon of the neurons to form a protective layer called the myelin sheath. The myelin sheath is the outer protective layer of a nerve cell that provides insulation for the smooth transmission of the electric impulses through the axon. The myelin increases the speed of conduction of the electric signals as the fatty material prevents the electric impulses from leaking out. The myelin sheath is essential as the axons of a human nerve cell can be as long as a meter, and it requires proper insulation to conduct the signals with ease.