Difference Between Neurons and Neuroglia

Main Difference – Neurons vs Neuroglia

Neurons and neuroglia are the two types of cells that make up the nervous system of higher vertebrates. The main difference between neurons and neuroglia is that neurons are involved in the signal transduction in the nervous system whereas neuroglia are the supporting cells of the neurons. Neurons are the structural and functional unit of the nervous system. Neurons are also called nerve cells. The three types of neurons in the body are motor neurons, sensory neurons, and interneurons. Different types of neuroglia can be identified in the central nervous system (CNS) and the peripheral nervous system (PNS). The neuroglia found in the CNS are astrocytes, oligodendrocytes, microglial cells, and ependymal cells. The neuroglia found in the PNS are Schwann cells and the satellite cells.

Key Areas Covered

1. What are Neurons
      – Definition, Characteristics, Types, Function
2. What are Neuroglia
      – Definition, Characteristics, Types, Function
3. What are the Similarities Between Neurons and Neuroglia
      – Outline of Common Features
4. What is the Difference Between Neurons and Neuroglia
      – Comparison of Key Differences

Key Terms: Astrocytes, Central Nervous System (CNS), Ependymal Cells, Interneurons, Microglial Cells, Motor Neurons, Neuroglia, Neuron, Oligodendrocytes, Peripheral Nervous System (PNS), Satellite Cells, Schwann Cells, Sensory Neurons, Signal Transduction

What are Neurons

Neurons are the structural and functional units of the nervous system in vertebrates and invertebrates upward from cnidarians. They are involved in the transition of electrical impulses, coordinating and controlling various functions of the body. Typically, a neuron consists of a cell body with a large nucleus. The cytoplasm of a neuron consists of Nissl granules. The Nissl granules are formed from the rough endoplasmic reticulum and rosettes of free ribosomes. These granules are involved in the protein synthesis. Two or more long fibers, called axons, extend from the cell body. The axons carry nerve impulses away from the cell body. A bundle of nerve fibers forms a nerve.

Figure 1: Motor Neuron

The three types of neurons in the body are sensory neurons, motor neurons, and interneurons. Both sensory and motor neurons are components of the PNS. The sensory neurons carry nerve impulses from the sensory organs to the CNS. The motor neurons carry nerve impulses from the CNS to the effector organ. The interneurons are found in the spinal cord, interconnecting the sensory and motor neurons at the spinal cord. The anatomy of a typical motor neuron is shown in figure 1.

What are Neuroglia

Neuroglia refers to the supportive cells of the nervous system. They provide the structural support to the neurons. Furthermore, neuroglia cells provide nutrients and oxygen to the neuron cells. Some of the glial cells such as Schwann cells and oligodendrocytes are myelinated and are involved in providing the electrical insulation through the axons. Different types of neuroglia are found in the CNS and PNS.

Neuroglia in the Central Nervous System

Astrocytes

The astrocytes are star-shaped cells with numerous projections. The neurons and their synaptic ends are tightly held by the projections of astrocytes. These projections attach the neurons to the blood capillaries, facilitating the transport of nutrients and oxygen. Astrocytes regulate the external chemical environment of the neurons by recycling the neurotransmitters and balancing the amounts of ions.

Oligodendrocytes

The oligodendrocytes are the cells that wrap around the axons of the neurons in the CNS. They have less projections than oligodendrocytes. The projections of oligodendrocytes wrap several times around the axon. Since they possess several projections, each projection wraps around the axons of several neurons. The formation of the myelin sheath around the axon insulate the axons and decreases the time taken to the signal transduction through the axon.

Microglial Cells

The microglial cells have thorny processes, touching the neighboring neurons. These cells perform a phagocytic function by removing the neuron debris. They are capable of detecting the injuries of the neurons.

Ependymal Cells

The ependymal cells are found in the ventricles of the CNS. These cells serve as a permeable barrier between the underlying cells and the cerebrospinal fluid (CSF). The movement of cilia in the ependymal cells are involved in the circulation of the CSF.

Difference Between Neurons and Neuroglia

Figure 2: Types of Neuroglia

Neuroglia in the Peripheral Nervous System

Schwann Cells

The Schwann cells are functionally analogous to the oligodendrocytes in the CNS since they insulate the nerve axons. In addition, Schwann cells are functionally analogous to the microglial cells in the CNS, which clear the nerve debris.

Satellite Cells

The satellite cells are functionally analogous to astrocytes in the CNS as both regulate the external environment of the neurons in the PNS. These cells are highly sensitive to the injuries and produce the chronic pain.

Similarities Between Neurons and Neuroglia

Both neurons and neuroglia are the two types of cells that make up the nervous system.
Both neurons and neuroglia are involved in coordinating and controlling various functions of the body.

Definition

Neurons: Neurons are the cells in the nervous system, which receive and transmit nerve impulses.

Neuroglia: Neuroglia are the supporting cells in the nervous system, which provides mechanical and structural support to neurons, supply nutrients and oxygen to neurons, and provide electrical insulation through axons of the neuron.

Significance

Neurons: Neurons are the functional unit of the nervous system.

Neuroglia: Neuroglia are the supporting cells of the neurons.

Function

Neurons: Neurons are involved in the signal transduction.

Neuroglia: Neuroglia provide nutrients to neurons and produce the packaging media between neurons.

Granules

Neurons: Neurons have Nissal granules.

Neuroglia: Neuroglia do not have granules.

Axons

Neurons: Neurons have long, slender projections called axons, which conduct the nerve impulses.

Neuroglia: Neuroglia do not have axons. However, some neuroglia comprise small, slender projections.

Synapses

Neurons: Neurons form synapses between two neurons, and between neurons and the sensory or effector organs.

Neuroglia: Neuroglia do not form synapses.

Size

Neurons: Neurons can be 4 μm to 1 mm.

Neuroglia: Neuroglia are smaller than neurons.

Quantity

Neurons: Around 100 billion neurons are present in the human body.

Neuroglia: The number of neuroglia in higher vertebrates is 5 to 10 times the number of neurons.

In a Mature Nervous System

Neurons: Most neurons are incapable of multiplying and differentiating in a mature nervous system.

Neuroglia: Neuroglia in a mature nervous system are capable of multiplying by themselves.

With Age

Neurons: The number of neurons remains the same with age.

Neuroglia: The number of neuroglia is reduced with age.

Types

Neurons: The three types of neurons are sensory neurons, motor neurons, and interneurons.

Neuroglia: The neuroglia in the CNS are astrocytes, oligodendrocytes, microglial cells, and ependymal cells. The neuroglia in the PNS are Schwann cells and satellite cells.

Conclusion

Neurons and neuroglia are two types of cells found in the nervous system. Neurons are the structural and functional unit of the nervous system. They receive and transmit nerve impulses to coordinate and control the functions of the body. The three types of neurons are sensory neurons, motor neurons, and interneurons. Neuroglia are the supportive cells of the nervous system. They also help to supply nutrients and oxygen to the neurons. One of the main functions of the neuroglia is to insulate the nerve axons, increasing the speed of the transduction of the nerve impulses. Different types of neuroglia can be found in CNS and PNS. The main difference between neurons and neuroglia is the structure and the function of each type of cells in the nervous system.

Reference:

1.“Neuron.” Encyclopædia Britannica, Encyclopædia Britannica, inc., Available here. Accessed 21 Aug. 2017.
2.“Neuroglia of the Central Nervous System – Boundless Open Textbook.” Boundless, 9 Nov. 2016, Available here. Accessed 21 Aug. 2017.

Image Courtesy:

1. “Blausen 0657 MultipolarNeuron” By BruceBlaus – Own work (CC BY 3.0) via Commons Wikimedia
2. “Blausen 0870 TypesofNeuroglia” By “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia