Key Differences – Neurilemma vs Myelin Sheath
Before discussing the difference Between Neurilemma and Myelin Sheath, let us first briefly look at the function of the nervous system. Animals gather information from the environment and communicate with all the parts of the body through the nervous system. It is mainly made up of nerve fibers and nerve cells, which are localized mainly in the brain and spinal cord. Apart from the nerve cells (neurons), the nervous system is supported by two types of cells; Schwann cells and Oligodendrocytes, which are commonly known as neuroglia. Neurilemma and myelin sheath are two important cellular components derived from neuroglia. The key difference between Neurilemma and the myelin sheath is that Neurilemma is the cytoplasm and the nuclei of the Schwann cells lying outside the myelin sheath while Myelin sheath is a modified cellular membrane wrapped around the axon of the neurons. In this article, the difference between neurilemma and myelin sheath is described further.
What is Neurilemma?
The cytoplasm and the nuclei of the Schwann cells which lie outside the myelin sheath are collectively called the neurilemma. The neurilemma is only present in the peripheral nervous system and is absent in the central nervous system due to the lack of Schwann cells. The neurilemma is important for the regeneration process of nerves. It is believed that the lack of neurilemma accounts for the inability of the regeneration of central nervous system.
What is Myelin Sheath?
Myelin sheath is formed by consecutive wrappings of Schwann cell membrane around the axon of a neuron. In the peripheral nervous system, Schwann cells produce the myelin sheath, while oligodendrocytes produce the myelin in central nervous system. Myelinated axons in the central nervous system produce the white matter, whereas that in the peripheral nervous system produce nerve fibers. Myelin sheath protects and insulates the axon. It is made up of phospholipids. Myelin sheaths are interrupted at regular intervals along the nerve fiber and are called nodes of Ranvier.
What is the difference between Neurilemma and Myelin Sheath?
Definition of Neurilemma and Myelin Sheath
Neurilemma: Neurilemma is the cytoplasm, and the nuclei of the Schwann cells lie outside the myelin sheath.
Myelin sheath: Myelin sheath is a modified cellular membrane wrapped around the axon of the neurons.
Characterisitcs of Neurilemma and Myelin Sheath
Neurilemma: In the central nervous system, Schwann cells form the myelin sheath, while, in the peripheral nervous system, myelin is formed by oligodendrites.
Myelin sheath: Neurilemma is formed by Schewann cell.
Neurilemma: Neurilemma nourishes help for the regeneration of nerves.
Myelin sheath: Myelin sheath protects and insulates the axon.
Myelin sheath: Myelin sheath is present in both central and peripheral nervous system.
Neurilemma: Neurilemma is only present in the peripheral nervous system.
Image Courtesy: “Complete neuron cell diagram en” by LadyofHats – Own work. Image renamed from Image:Complete neuron cell diagram.svg. (Public Domain) via Wikimedia Commons
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