What is the Difference Between Axolemma and Neurilemma

The key difference between axolemma and neurilemma is that axolemma is the cell membrane of the axon while neurilemma is the outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron.

Neurons are nerve cells that send signals all over the body to allow people to engage in all types of activities, including breathing, talking, eating, walking, and thinking. In neuroscience, neurons consist of a large cell body and nerve fibers. Axon is one nerve fiber and an elongated extension for sending impulses. Dendrites are nerve fibers that usually receive impulses. These impulses typically travel from one axon, cross a synapse, and reach the dendrite of another cell. Axolemma and neurilemma are two structures that are connected to the nervous system and are often discussed in neuroscience. However, they are different structures and perform different functions.

What is Axolemma?

Axolemma is the cell membrane of the axon. The axon is the branch of a neuron through which nerve signals are transmitted. Axolemma is a three-layered bilipid membrane. It has a thickness of 8nm. As axolemma is a phospholipid bilayer membrane, the charged ions/particles cannot directly pass through it. Therefore, specialized transmembrane proteins (sodium/potassium pump and ion channels) that sit within the axolemma are required to assist the charged ions/particles across the membrane.  This will help to generate transmembrane potentials that will ultimately generate an action potential.

Figure 01: Myelinated Neuron

The primary function of an axolemma is to relay signals between a neuron and its’ Schwann cells. Furthermore, these signals control the proliferative and myelin-producing functions of the Schwann cells and play a role in the regulation of the size of the axon.

What is Neurilemma?

Neurilemma is the cytoplasmic sheath of a Schwan cell that is present around the myelin sheath of an axon. In fact, a neurilemma is a layer of Schwann cells wrapped around the axon. It is a coil of a Schwann cell, including two layers of plasma membrane and the cytoplasm between them. Normally, a Schwann cell produces a myelin sheath around the nerve fiber. The neurilemma is only the outermost coil of the Schwann cell surrounding the myelin.

Figure 2: Medullated Nerve Fibers

In the central nervous system, axons are usually myelinated by oligodendrocytes. Therefore, they lack neurilemma. Neurilemma’s primary function is to serve as a protective function for peripheral nerve fibers. Neurilemoma is a tumor that affects neurilemma.

What are the Similarities Between Axolemma and Neurilemma?

• Axolemma and neurilemma are two structures that are connected to the nervous system.
• Both are often discussed in neuroscience.
• Both can be identified in the peripheral nervous system.
• They can be diagnosed through a pelvic examination.
• Both can be affected by different diseases.

What is the Difference Between Axolemma and Neurilemma?

Axolemma is the cell membrane of the axon, while neurilemma is the outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron. Thus, this is the key difference between axolemma and neurilemma. Furthermore, axolemma is not nucleated, whereas neurilemma is nucleated.

The infographic below presents the differences between axolemma and neurilemma in tabular form for side-by-side comparison.

FAQ: Axolemma and Neurilemma

What is the neurilemma also known as?

Neurolemma, sheath of Schwann, or Schwann’s sheath are synonyms of neurilemma.

What is an axoplasm?

Cytoplasm within the axon of a neuron (nerve cell) is known as axoplasm.

What is axolemma structure?

The axolemma is composed of a lipid bilayer and a submembrane skeleton, which is formed by the protein spectrin and actin.

Summary – Axolemma vs. Neurilemma

Axolemma and neurilemma are two structures that are connected to neurons and the nervous system. Axolemma is the cell membrane of the axon, while neurilemma is the outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron. Axolemma relays signals between a neuron and its Schwann cells, while neurilemma serves as a protective function for peripheral nerve fibers. So, this summarizes the difference between axolemma and neurilemma.