A coating of myelin covers the nerves, allowing electrical impulses to travel quicker and more efficiently. Without myelin, conditions like multiple sclerosis can occur. Myelin location is critical for the proper functioning of the central and peripheral nervous systems. In this article, we will explore the different areas of the body where myelin is found.
What is Myelin?
Myelin is a protein and lipid layer wrapped around the nerve fibers, also known as axons, of the central and peripheral nervous systems. It forms an insulating, protective sheath. Multiple segments of myelin are produced by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. The formation of myelin aids in improving nerve impulse speed and energy efficiency.
Structure of Myelin
Myelin structure varies depending on where it is located in the body. It is a layer or coating made up of phospholipids and proteins that spiral around the nerve fibers. The exact number of layers can vary, but it is typically between 40 and 100 layers in total.
Myelin layers have small gaps known as nodes of Ranvier or nerve nodes, interspersed between them. These nodes assist in electrical impulses moving along nerves more efficiently, speeding up their transmission rate.
Where is Myelin Found?
Now that we understand the basic definition of myelin and its structure, it is time to explore where it is found in the body.
Central Nervous System
Myelin in the central nervous system is produced by oligodendrocytes that wrap themselves around several axons in a process termed myelination. Oligodendrocytes are specialized glial cells that help insulate the nerves to prevent leaks and loss of energy. It is worth noting that some axons lack myelin entirely, while others possess several segments of it.
Here are some locations in the central nervous system where myelin is found:
- Brain: Myelin covers many axons in the brain, and it is especially dense in regions like the cortex, basal ganglia, and cerebellum.
- Spinal Cord: The spinal cord also contains many myelinated axons, and they are concentrated in the white matter.
- Optic Nerve: The optic nerve is the pathway that carries visual information from the retina to the brain. It is entirely myelinated.
Peripheral Nervous System
Myelin in the peripheral nervous system is created by Schwann cells that wrap themselves around a single axon. One Schwann cell generates one segment of myelin along each axon, and the axon is not wrapped in other areas.
Locations in the peripheral nervous system where myelin is found include:
- Cranial Nerves: There are 12 pairs of cranial nerves that are directly connected to the brain. Each of these nerves has myelin covering the axons.
- Peripheral Nerves: Myelinated peripheral nerves cover the arms, legs, and torso, among other areas of the body. The ulnar nerve, for instance, is the longest and most extensive nerve bundle in the upper limb, and its axons are heavily myelinated.
Myelin and Associated Diseases
Myelin is essential for the proper functioning of the nervous system, and any condition that disrupts its formation or maintenance can have serious consequences. Diseases that affect myelin in various areas of the body can lead to either demyelination or dysmyelination.
Demyelination is the gradual loss of myelin in the nerves, leading to a disruption in nerve function. This condition leads to many diseases, including:
- Multiple Sclerosis: This autoimmune disease occurs when the immune system attacks myelin in the central nervous system, leading to damage and inflammation.
- Guillain-Barre Syndrome: This is a rare and often life-threatening disorder in which the immune system attacks peripheral nerves, resulting in muscle weakness and paralysis.
- Leukodystrophies: This group of genetic disorders affects the nervous system by damaging or disrupting the production of myelin.
Dysmyelination involves abnormal myelin formation and tends to occur during early development. This can cause a wide range of physical and cognitive impairments, like:
- Childhood Leukodystrophies: These rare disorders are mostly caused by genetic mutations that disrupt myelin formation or maintenance. Symptoms can range from motor and cognitive difficulties to blindness and deafness.
- Pelizaeus-Merzbacher Disease: This is a rare genetic disorder that affects myelin formation in the central nervous system, leading to developmental delays and severe neurological symptoms.
The Role of Myelin in Neurodegenerative Disorders
Research has shown that myelin play a vital role in the development of neurodegenerative diseases like Alzheimer’s, Parkinson’s, and Huntington’s disease. Experts have been studying the relationship between the immune system, inflammation, and myelin damage in the nervous system.
The results of these studies have been inconclusive, but they suggest that myelin damage and inflammation may play a significant role in the development of neurodegenerative disorders.
We hope this article has given you a better understanding of where myelin is located in the human body and its importance in the nervous system. Its different locations have distinct features, which vary depending on individual factors.
- What is myelin? Myelin is a protein and lipid layer wrapped around the nerve fibers, also known as axons, of the central and peripheral nervous systems.
- What is the function of myelin? Myelin forms an insulating, protective sheath, improving nerve impulse speed and energy efficiency.
- What are the consequences of demyelination? Demyelination causes nerve function disruption and leads to various diseases like Multiple Sclerosis, Guillain-Barre syndrome, and Leukodystrophies.
- What is dysmyelination? Dysmyelination is abnormal myelin formations that can lead to physical and cognitive impairments.
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