Which cells myelinate nerve fibers in the peripheral nervous system?

Appeared in: MP CHO - 2022

Explanation

Schwann cells are the specific glial cells responsible for producing the myelin sheath in the Peripheral Nervous System (PNS).
Each Schwann cell wraps around a single segment of an axon, forming an internodal segment of myelin.
This process of myelination allows for saltatory conduction, which significantly increases the speed of nerve impulse transmission.
Schwann cells also play a crucial role in the regeneration of damaged peripheral nerves.

Option A: This is a general term. 'Glial cell' refers to all supporting cells of the nervous system, which includes Schwann cells, astrocytes, and oligodendrocytes. The question asks for the specific cell, making this answer too broad.
Option C: Astrocytes are glial cells found in the Central Nervous System (CNS), not the PNS. Their main functions are to provide structural support, maintain the blood-brain barrier, and regulate the neuronal environment; they do not myelinate axons.
Option D: Oligodendrocytes are responsible for myelination, but they do so in the Central Nervous System (CNS), not the Peripheral Nervous System (PNS).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Myelination in the Peripheral Nervous System as background academic context rather than a clinical decision trigger.
Understanding the difference between Schwann cells and oligodendrocytes is critical for diagnosing and managing demyelinating diseases like Guillain-Barré Syndrome (PNS) and Multiple Sclerosis (CNS).
Nurses must recognize the different clinical presentations. GBS often presents with ascending paralysis (from feet up), while MS symptoms are varied and depend on the location of CNS lesions.
Knowledge of nerve regeneration is also key. Damage to peripheral nerves (involving Schwann cells) has a potential for recovery, whereas damage to the CNS (involving oligodendrocytes) is generally permanent.

How to Approach the Question

First, identify the key terms in the question: 'myelinate' and 'peripheral nervous system (PNS)'.
Recall the different types of glial (support) cells in the nervous system and their primary locations (CNS vs. PNS).
Evaluate each option based on these key terms.
Option A, 'Glial cell', is too general. The question seeks a specific cell type.
Option B, 'Schwann cells', are known to be in the PNS and are responsible for myelination.
Option C, 'Astrocytes', are in the CNS and have support functions, but do not myelinate.

Concept Tested & Keywords

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E6 Anatomy Grays 43e Vol 1 Part 1 p. 90-92

E6 Medicine Harrison 22e Part 2 p. 1301-1303

E6 Anatomy Applied Ashalatha 4e p. 405-407

Practise the full MP CHO - 2022

Attempt every question from this paper in a timed mock, then review the full solution for each one.