Main Difference – Nerve vs Neuron
Nerve and neuron are two structural components that make up the nervous system of vertebrates. The nervous system helps animals to respond to both external and internal stimuli. The information gathered by the sensory receptors in the body are sent to the central nervous system by the neurons in the peripheral nervous system. The central nervous system is also composed of neurons. The relevant responses are sent to the effector organs with the aid of peripheral nervous system. The main difference between nerve and neuron is that a nerve is a bundle of neurons along with their connective tissue sheaths, blood vessels, and lymphatics whereas a neuron is a cell of the nervous system that conducts nerve impulses.
Key Areas Covered
1. What is a Nerve
– Definition, Types, Functions
2. What is a Neuron
– Definition, Types, Functions
3. What are the Similarities Between Nerve and Neuron
– Outline of Common Features
4. What is the Difference Between Nerve and Neuron
– Comparison of Key Differences
Key Terms: Central Nervous System, Cranial Nerves, Endoneurium, Epineurium, Interneurons, Mixed Nerves, Motor Nerves, Motor Neurons, Nerve, Neuron, Peripheral Nervous System, Sensory Nerves, Sensory Neurons, Spinal Nerves
What is a Nerve
A nerve is a bundle of axons of a large number of neurons in the peripheral nervous system. A nerve is a wire-like structure which transmits nerve impulses in the form of chemical and electrical signals between central nervous system and sensory or effector organs. Each axon in a nerve is wrapped with a connective tissue layer called endoneurium. The axon bundle of the nerve is wrapped by a connective tissue layer called epineurium. A fascicle is a group of neurons. A cross section of a nerve is shown in figure 1.
Figure 1: A Cross-section of a Nerve
Three types of nerves are found based on the direction of transmitting signals within the nervous system. They are sensory nerves, motor nerves, and mixed nerves. Sensory nerves are also known as afferent nerves, and carry information from the sensory receptors into the central nervous system. Motor nerves carry nerve impulses from the central nervous system to the effector organs. Mixed nerves contain both sensory and motor neurons within the same nerve.
Based on the way they are connected to the central nervous system, two types of nerves can be identified as cranial nerves and spinal nerves. The parts of the head are innervated by cranial nerves, which are connected with the brain. Twelve cranial nerves are found in humans. Most of the body parts are innervated by spinal nerves, which are connected to the spinal cord. Nerve fibers can be divided based on their diameter, velocity of the signal conduction, and the myelinated state of the axons as well. The group A nerves have a large diameter. They are myelinated and have a high signal conduction velocity. The group B nerves have a small diameter. They are also myelinated, but their conduction velocity is low. The group C nerves are unmyelinated, with a small diameter, and low conduction velocity. The nerves in the left upper limb of humans are shown in figure 2.
Figure 2: Nerves in the Left Upper Limb
What is a Neuron
A neuron is the functional unit of the nervous system which transmits nerve impulses between the central and peripheral nervous systems. There are three types of neurons based on their function in the nervous system. They are sensory neurons, motor neurons, and interneurons. The sensory neurons transmit nerve impulses generated at the sensory receptors to the central nervous system. The motor neurons transmit nerve impulses from the central nervous system to the effector organ. The interneurons are also called association neurons, and they connect sensory and motor neurons at the central nervous system. Neurons allow the communication and coordination of functions in the body. The nerve impulses are transmitted in the form of electrical and chemical signals through the neurons.
A neuron consists of three characteristic components. They are the cell body or soma, axon, and dendrites. The cell body of the neuron consists of the cellular structures of a eukaryotic cell, including a nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus. The dendrites are tiny projections of the cell body. They pick signals from the other cells. The axon is a long, thin fiber extended from the cell body. The branches of the axon at its terminal are the synaptic knobs. Most axons are wrapped with a fatty myelin sheath produced by Schwann cells. The small gaps within the myelin sheath are called the nodes of Ranvier. The structure of a typical nerve cell is shown in figure 3.
Figure 3: A Typical Neuron
Similarities Between Nerve and Neuron
- Both nerve and neuron are structural and functional components of the nervous system in vertebrates.
- Both nerve and neuron are involved in transmitting nerve impulses between sensory or effector organs and the central nervous system.
Difference Between Nerve and Neuron
Definition
Nerve: A nerve is a whitish fiber of neuron cells which carry impulses to the central nervous system and from the central nervous system to the effector organs.
Neuron: A neuron is a specialized cell involved in transmitting nerve impulses.
Found in
Nerve: Nerves are found only in the peripheral nervous system.
Neuron: Neurons are found in both peripheral and central nervous systems.
Structure
Nerve: A large number of nerve fibers are grouped together to form a nerve along with blood vessels and lymphatics.
Neuron: A neuron is composed of an axon, cell body, and dendrites.
Significance
Nerve: The nerve acts a conducting zone for transporting signals.
Neuron: The chemical and electronic signals are generated in the neuron.
Types
Nerve: Cranial nerves, spinal nerves, sensory nerves, and motor nerves are the types of nerves in the body.
Neuron: Sensory neurons, motor neurons, and interneurons are the types of neurons in the body.
Conclusion
Nerve and neuron are two components of the nervous system of a vertebrate. The neuron is the cell that makes up the nervous system. The nerve is a bundle of neurons. The neuron is responsible for generating nerve impulses in the form of chemical and electrical signals whereas nerves provide the environment for conducting the nerve impulses. Thus, the main difference between nerve and neuron is their application in the nervous system in vertebrates.
Reference:
1.”Nerves : Various Types of Nerves and their Function in Human Body @Byjus.” Biology. Byjus Classes, 07 Sept. 2016. Web. Available here. 03 July 2017.
2.”Classification of Nerves – Boundless Open Textbook.” Boundless. N.p., 12 Oct. 2016. Web. Available here. 03 July 2017.
3. Lodish, Harvey. “Nerve Cells.” Molecular Cell Biology. 4th edition.U.S. National Library of Medicine, 01 Jan. 1970. Web. Available here. 03 July 2017.
4.”Nerve Cell.” Nerve Cell | Structure, Nerve Cell Function | [email protected]. N.p., n.d. Web. Available here. 03 July 2017.
Image Courtesy:
1. “1319 Nerve StructureN” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia
2. “Nerves of the left upper extremity” By Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body (See “Book” section below)Bartleby.com: Gray’s Anatomy, Plate 816 (Public Domain) via Commons Wikimedia
3. “Neuron” (CC BY-SA 3.0) via Commons Wikimedia
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