Understand Difference

Unveiling the Neurilemma and Myelin Sheath: Building Blocks of the Nervous System

Introduction to

Neurilemma and

Myelin Sheath

The human nervous system plays a fundamental role in connecting the body’s various organs and tissues, ensuring that they work together to sustain our lives. This complex network comprises millions of nerve cells or neurons that transmit electrical signals to communicate and coordinate various functions of the body.

To ensure optimal functioning of these neurons, they require a high degree of insulation, which is provided by the myelin sheath, an insulating layer that covers the nerve fibers. In addition to the myelin sheath, the neurilemma also plays a crucial role in the function and health of the peripheral nervous system.

This article aims to provide a more in-depth understanding of the neurilemma and myelin sheath, including their functions and features.

The

Function of the Nervous System

The nervous system comprises two major components: the central nervous system (CNS), which is composed of the brain and spinal cord, and the peripheral nervous system (PNS), which includes all the nerves outside the spinal cord and brain. The nervous system’s primary function is to regulate and coordinate the body’s various activities, such as movement, sensation, and thoughts.

In this regard, the nervous system serves as a communication network that connects various body parts through a complex web of neurons.

Nerve Cells (Neurons) and Neuroglia

Nerve cells, or neurons, form the basis of the nervous system. They are specialized cells that communicate through electrical and chemical signals.

Neurons have specialized structures called dendrites, which receive signals from other cells, and axons, which transmit signals to other cells. In addition to neurons, neuroglia, also called glial cells, are the most abundant cell type in the nervous system.

Neuroglia performs various functions to support and maintain the neurons, such as providing insulation, metabolizing nutrients, and removing waste products.

Definition of

Neurilemma and

Myelin Sheath

The neurilemma is a thin layer of cytoplasm and nuclei of Schwann cells that surrounds some axons in the PNS. It is only present in peripheral nerves and is found only in the cranial, spinal, and autonomic ganglia.

The neurilemma performs a vital role in the regeneration of nerve fibers after damage. The myelin sheath, on the other hand, is a specialized insulating layer that surrounds the axons of many neurons.

The myelin sheath is composed of either Schwann cells or oligodendrocytes, depending on whether it is in the PNS or CNS. The myelin sheath helps increase the speed of nerve impulses by enabling the electric current to travel more efficiently along the axon.

Neurilemma

The neurilemma is a thin layer of cytoplasm and nuclei of Schwann cells that surrounds some axons in the PNS. The neurilemma is a crucial component of the peripheral nervous system, as it plays a crucial role in the regeneration of damaged nerves.

After a nerve injury, the axon’s distal end (away from the cell body) degenerates, but the neurilemma remains intact. The intact neurilemma functions as a guide for the axon to regenerate and reconnect with its target cells, which allows for neural regeneration to be possible.

The neurilemma is composed of Schwann cells, which are specialized glial cells. Schwann cells are located outside the myelin sheath, and they wrap around the axon, providing structural support and insulation.

In addition, Schwann cells aid in the regeneration of damaged axons in peripheral nerves. After an injury, Schwann cells dedifferentiate and migrate to the site of injury, where they form a pathway for the growing axon.

Only present in the peripheral nervous system, the neurilemma plays a crucial role in the regeneration of damaged nerves. A nerve injury can cause the axon to degenerate and separate from the cell body, disrupting the flow of electrical signals in the nervous system.

However, the neurilemma remains intact, providing a pathway for the growing axon to reconnect and regenerate. This feature highlights the importance of the neurilemma in aiding nerve regeneration.

Conclusion

In conclusion, the neurilemma and the myelin sheath are both crucial components of the nervous system. The neurilemma is a thin layer of cytoplasm and nuclei of Schwann cells that surrounds some axons in the PNS, playing a vital role in the regeneration of damaged nerves.

The myelin sheath, on the other hand, is a specialized insulating layer that surrounds axons, and it helps increase the speed of the transmission of nerve impulses along the axon. Understanding the role of these components in the nervous system is essential for appreciating the complexity of the structure and function of the nervous system.

Myelin Sheath

The myelin sheath is an insulating layer that covers the axons of many neurons and is composed of phospholipids. Myelin allows for the efficient and rapid propagation of electrical impulses along an axon by decreasing the leakage of ions and increasing the speed with which action potentials can be transmitted.

Formation

In the peripheral nervous system, the myelin sheath is formed by consecutive wrappings of the Schwann cell membrane around the axon. Schwann cells produce myelin in the PNS, and each cell wraps one axon segment.

In contrast, in the central nervous system (CNS), the myelin sheath is formed by oligodendrocytes that form multiple myelin segments around one membrane. This arrangement allows for compact and efficient myelin formation in the CNS.

Function

The myelin sheath serves as a critical protective layer for the axons, providing insulation from other surrounding nerve fibers. This insulation prevents cross-talk between different nerve impulses, which can occur when electrical impulses jump between closely packed axons.

The myelin sheath effectively acts as an insulator for an axon, minimizing the loss of charge that occurs as electrical impulses propagate. Myelin facilitates the saltatory conduction of electrical impulses, which involves the jumping of impulses from one node of Ranvier to the next, and this improves the speed at which signals are transmitted.

The greater the length of the myelin, the faster an impulse can travel along the length of the axon.

Nodes of Ranvier

Nodes of Ranvier are small gaps that occur on the myelin sheath at regular intervals along the axon. The function of these nodes is to allow for the propagation of electrical impulses in the axon.

They enable action potentials to be regenerated in the absence of myelin, as the ions required for conducting electrical impulses can pass freely through the cytoplasm of the axon at these nodes. Therefore, because of the nodes of Ranvier, the electric charge carried by the action potential can “jump” to the next node, which results in faster and more efficient conduction of electrical impulses along the axon.

Differences Between

Neurilemma and

Myelin Sheath

While the neurilemma and myelin sheath are both components of the nervous system, there are several differences that set them apart.

Definition of

Neurilemma and

Myelin Sheath

The neurilemma is a thin layer of cytoplasm and nuclei of Schwann cells that surrounds some axons in the peripheral nervous system. The myelin sheath, on the other hand, is a specialized insulating layer that surrounds axons, present in both the peripheral and central nervous systems.

Formation (Schwann cells vs. Oligodendrocytes)

In the peripheral nervous system, the neurilemma is formed by Schwann cells.

Schwann cells develop a layer of cytoplasm outside the myelin sheath, forming what is known as the neurilemma. The myelin sheath, on the other hand, is produced by Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system.

Oligodendrocytes form myelin segments that wrap around and insulate axons in the CNS.

Function (Nerve Regeneration vs. Protection and Insulation)

The primary function of the neurilemma is to facilitate nerve regeneration in peripheral nerves.

After injury, the intact neurilemma forms a pathway for the growing axon to reconnect and regenerate. Myelin, on the other hand, serves as a critical protective layer for the axons, providing insulation from other surrounding nerve fibers.

The myelin sheath also facilitates the rapid propagation of electrical impulses along the axon. Presence (Only Peripheral Nervous System vs.

Both Central and Peripheral Nervous System)

The neurilemma is only present in peripheral nerves, while the myelin sheath is present in both the CNS and PNS. Schwann cells produce myelin in the PNS, and each cell wraps one axon segment.

In contrast, in the CNS, oligodendrocytes form multiple myelin segments around one membrane, allowing for compact and efficient myelin formation.

Conclusion

In conclusion, the neurilemma and myelin sheath are two essential components of the nervous system that are involved in different functions. The neurilemma functions in nerve regeneration in the peripheral nervous system, while the myelin sheath provides protection, insulation, and efficient electrical impulses propagation in both the central and peripheral nervous system.

The formation of the neurilemma is through Schwann cells in the PNS, while the myelin sheath is produced by Schwann cells in the PNS and oligodendrocytes in the CNS. Understanding these components’ features is essential to appreciate their roles and how they contribute to efficient neural function.

In conclusion, the neurilemma and myelin sheath are crucial components of the nervous system that play significant roles in ensuring optimal nerve function and health. The neurilemma aids in the regeneration of damaged nerves in the peripheral system, while myelin sheath provides protection, insulation, and facilitates efficient electrical impulse propagation in both the central and peripheral nervous systems.

Schwann cells produce myelin in the peripheral nervous system while oligodendrocytes produce it in the central nervous system. Understanding these components’ features is crucial to appreciate their roles, and how they contribute to efficient neural function.

Advances in research into myelin and neurilemma may have significant implications for the treatment of nervous system disorders and rehabilitation from nerve injury.

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