Neuron: Definition, Classification, Structure, & Functions

Do you know which are the longest cells in the human body? Neurons are the longest cell in the human body. Neurons are a minor component of the nervous system; they are also known as nerve cells. Neurons are specialized cells designed to communicate information to other nerve cells, muscle, and gland cells.

They are responsible for transmitting information throughout the human body. They use electrical and chemical signals to coordinate all the essential functions of life. The basic unit of the human nervous system is the neuron. In this article, we will explore the definition of neuron, types of neuron, diagram of neuron, neuron’s structure, and neuron’s functions. Continue reading to find out more!

What is Neuron and its Function?

Neurons are the basic and fundamental units of the nervous system which are responsible for transmitting signals to establish communication between the central nervous system and the body. Neurons are also called nerve cells. Neurons use electrical and chemical signals to coordinate all the essential functions of life.

What are the 3 Types of Neurons?

Neurons are of three types based on the functions:

1. Sensory Neurons or Afferent Neurons
2. Motor Neurons or Efferent Neurons
3. Interneurons

Neurons are of four types based on the structure:

1. Bipolar Neurons
2. Multipolar Neurons
3. Unipolar Neurons
4. Pseudo unipolar Neurons

Neuron Diagram

Here we provide the description of human neurons along with the Neuron diagram:

Neuron Structure

The main three parts of a neuron are the cell body or soma, axon, and dendrite. These parts are responsible for transmitting chemical and electrical signals.

1. Cell body or Soma: The cell body or Soma is also called a cyton. It contains a nucleus and cytoplasm that connects to dendrites. It carries signals to the other neurons and controls all the functions of the cell.
2. Axon: Axon is a part of a nerve cell or neuron that carries nerve impulses away from the cell body. A neuron typically has one long, slender projection called an axon. Most axons of vertebrates are enclosed in a myelin sheath.
3. Dendrite: Dendrites are root-like projections at the beginning of the neuron that help receive and process signals to the cell body.

Other than the basic parts of a neuron there are some important structures that are also present in the neuron.

1. Axon Hillock: The axon hillock is the region where the axon is connected to the soma or the cell body. It considered being the originating point or the initial segment of the axon.
2. Schwann cell: Schwann is various glial cells present in the peripheral nervous system. They supply the myelin for the peripheral nervous system.
3. Myelin sheath: Myelin is a white insulating sheath that forms around the axon in most neurons. It is covered by an outermost thin sheath called neurilemma.
4. Nodes of Ranvier: The gaps present between the myelin sheath are called Nodes of Ranvier.
5. Axon Terminals: Axon terminals are the button-like structure found at the end of the axon and placed near the dendrites. Axon terminal contains certain chemicals called neurotransmitters.
6. Synapses: Synapses are the gaps present between the axon of one neuron and the dendrites of another neuron. It allows a neuron to transmit signals to another neuron.

Fun Fact!

The human spinal cord has \(13,500,000\) neurons.

Functions of Neurons

The functions of neurons are mentioned below:

1. Neurons are the nerve cells that send and receive signals from the human brain.
2. They have specific projections called axons to transmit electrical and chemical signals.
3. In chemical synapses, electrical signals are converted into chemical signals or neurotransmitters. They are biological junctions through which signals are transmitted from one neuron to another or non-neuronal cells such as muscles and glands. Chemical synapses permit neurons to form circuits within the central nervous system.
4. In electrical synapses,  two neurons are connected by a gap junction. The ion channels can flow through these gap junctions. Impulse transmission in electrical synapses is much faster than chemical synapses. The membranes of pre and postsynaptic neurons are in very close proximity to electrical synapses. Therefore, electrical impulse can flow directly from one neuron to the other across these synapses.

Summary

Neurons are fundamental units of the nervous system. They are responsible for receiving sensory input from the outside world. The essential parts of neurons are the dendrite, an axon, cell body, or soma. They can be represented as the branches (dendrite), roots (axon), and trunks (cell body) of a tree (neuron). In a nutshell, for proper coordination among different organs of the human body, neurons play an important role.

Based on the structure, neurons can be classified into four types namely, multipolar, bipolar, unipolar, and pseudo unipolar. Based on the functions, neurons can be classified into 3 namely, Sensory Neurons or Afferent Neurons, Motor Neurons or Efferent Neurons, and Interneurons.

Learn About the Structure of Neuron

FAQs on Neurons

Q.1. What are the 3 types of neurons according to functions?
Ans: The 3 types of neurons according to functions are sensory neurons, motor neurons, and interneurons. 

Q.2. Define neurons.
Ans: Neurons are the basic and fundamental units of the nervous system and the brain. Neurons are also called nerve cells. They are responsible for sending and receiving signals from the central nervous system.

Q.3. What are the 7 parts of a neuron?
Ans: The 7 parts of a neuron are cell body, axon, dendrite, myelin sheath, Nodes of Ranvier, Schwann cell, and axon terminal. 

Q.4. What is the use of neurons?
Ans: Neurons are responsible for sending and receiving information throughout the human body using electrical impulses and chemical signals.

Q.5. What are the 4 types of neurons according to structure?
Ans: The 4 types of neurons according to the structure are multipolar, bipolar, unipolar, and pseudo unipolar.  

Q.6. How do neurons work?
Ans: Neuron produces nerve impulses that allow neurons to communicate with each other, computation to be performed and information to be processed.

Q.7. What is the gap between two neurons called?
Ans: The gap between two neurons is called a synapse.

Learn About Types of Neuron Based on Structure

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