Which of the following functions does the myelin sheath perform for a nerve cell?
A.
Insulation
B.
Regeneration
C.
Sensory perception
D.
Nutrition
The Correct Answer and Explanation is:
The correct answer is A. Insulation.
The myelin sheath is a critical component of the nervous system, playing a crucial role in the proper functioning of nerve cells. Here’s a detailed explanation of its function:
Myelin Sheath Overview
The myelin sheath is a fatty substance that wraps around the axons of many neurons, forming an insulating layer. This sheath is composed primarily of lipids (fats) and proteins, and it is produced by specialized cells: Schwann cells in the peripheral nervous system (PNS) and oligodendrocytes in the central nervous system (CNS).
Function of the Myelin Sheath
- Insulation: The primary function of the myelin sheath is to provide electrical insulation to the axon of the neuron. This insulation is essential because it prevents electrical impulses from leaking out of the neuron as they travel along the axon. Without this insulation, the electrical signals would dissipate, reducing the efficiency and speed of nerve signal transmission.
- Increased Conduction Speed: By insulating the axon, the myelin sheath allows electrical impulses to travel more quickly and efficiently. This is achieved through a process called saltatory conduction. In myelinated axons, the electrical impulses jump from one Node of Ranvier (gaps in the myelin sheath) to the next, significantly increasing the speed of signal transmission compared to unmyelinated axons where the impulse travels continuously along the axon.
- Protection: The myelin sheath also serves a protective role by shielding the axon from physical damage and potentially harmful substances in the extracellular environment.
Functions Not Performed by the Myelin Sheath
- Regeneration: The myelin sheath does not directly contribute to the regeneration of nerve cells. While it plays a role in the repair process in the PNS (where Schwann cells can assist in regenerating damaged axons), it is not responsible for the initial regenerative process.
- Sensory Perception: Sensory perception is primarily handled by sensory neurons and the brain’s interpretation of sensory input. The myelin sheath does not directly influence sensory perception.
- Nutrition: The myelin sheath does not provide nutritional support to the neuron. Nutrients are delivered to neurons through blood supply and other cellular mechanisms.
In summary, the myelin sheath’s primary function is insulation, which enhances the speed and efficiency of electrical signal transmission in the nervous system.