**Core Concept**
Oligodendrocytes are a type of glial cell in the central nervous system (CNS) responsible for producing and maintaining the myelin sheath, which is essential for the proper functioning of neurons. The myelin sheath acts as an electrical insulator, allowing for faster and more efficient transmission of nerve impulses.

**Why the Correct Answer is Right**
In the CNS, oligodendrocytes share a similar function with Schwann cells found in the peripheral nervous system (PNS). Both cells produce the myelin sheath, which facilitates the rapid transmission of nerve impulses. Oligodendrocytes can extend their processes to multiple axons, ensheathing them with myelin, whereas Schwann cells typically ensheath a single axon. This shared function highlights the importance of myelination in the nervous system.

**Why Each Wrong Option is Incorrect**
**Option A:** Astrocytes are a type of glial cell that provide nutrients and support to neurons but do not produce myelin.
**Option B:** Microglia are the resident immune cells of the CNS and play a role in phagocytosis and immune surveillance, but they do not produce myelin.
**Option C:** Ependymal cells line the ventricles and central canal of the spinal cord, producing cerebrospinal fluid, but they do not produce myelin.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that oligodendrocytes have a unique ability to myelinate multiple axons, which is crucial for the efficient transmission of nerve impulses in the CNS.

**Correct Answer: C. Microglia are the resident immune cells of the CNS and play a role in phagocytosis and immune surveillance, but they do not produce myelin.