**Core Concept:** Myelination is the process by which Schwann cells and oligodendrocytes in the peripheral and central nervous systems, respectively, enwrap and insulate neuronal axons to facilitate faster conduction of electrical impulses.

**Why the Correct Answer is Right:** The correct answer, C. Oligodendrocytes, are specialized glial cells responsible for producing and maintaining myelin sheaths around neuronal axons in the central nervous system (CNS). Oligodendrocytes are derived from neural crest cells and are involved in the maintenance, repair, and production of myelin.

**Why Each Wrong Option is Incorrect:**

A. Schwann cells are responsible for myelinating axons in the peripheral nervous system (PNS) and not the central nervous system.
B. Astrocytes are a type of glial cell, but they are not involved in myelination. Their main function is to support neurons, regulate the blood-brain barrier, and maintain the extracellular matrix.
D. Ependymal cells are the cells lining the ventricles and subarachnoid space in the central nervous system and are not related to myelination.

**Clinical Pearl:** Understanding the difference between Schwann cells, oligodendrocytes, astrocytes, and ependymal cells is crucial for understanding the distinct roles of different types of glial cells in the nervous system. This knowledge is essential in various medical fields, such as neurology, neuroscience, and neuropathology.

**Correct Answer:** C. Oligodendrocytes