**Question:** In CNS, the myelination is carried out by:

A. Oligodendrocytes
B. Astrocytes
C. Neurons
D. Microglia

**Correct Answer:** A. Oligodendrocytes

**Core Concept:**
The correct understanding of myelination in the Central Nervous System (CNS) is essential for NEET PG, USMLE, AIIMS, and FMGE students. Myelination is the process of creating myelin sheaths around neurons to enhance their efficiency and protect them. In the CNS, this process is primarily performed by oligodendrocytes, which are specialized glial cells. Glial cells, also known as neuroglia, play a crucial role in maintaining the homeostasis and support of neurons.

**Why the Correct Answer is Right:**
Oligodendrocytes are unique to the CNS, unlike Schwann cells in the peripheral nervous system (PNS), which are responsible for myelination there. They are derived from neural crest cells and are involved in the synthesis, assembly, and maintenance of the myelin sheaths. These sheaths are composed of compact myelin, which is an insulating lipid-rich structure that wraps around axons, enabling faster conduction of electrical impulses and protecting neurons from damage.

**Why Each Wrong Option is Incorrect:**

A. Astrocytes are another type of glial cell in the CNS, but they are not involved in myelination. Their primary role is to maintain the blood-brain barrier, provide structural support, and participate in neurotransmitter uptake.

B. Microglia are the immune cells and phagocytes of the CNS, responsible for maintaining tissue homeostasis and responding to injury or infection. They are not involved in myelination.

C. Neurons are the primary functional unit of the CNS and PNS, but they are not responsible for myelination. Neurons transmit electrical impulses and synthesize neurotransmitters, while myelination is performed by specialized cells like oligodendrocytes.

**Clinical Pearl:**
Understanding the distinction between myelination in the CNS and PNS is crucial for medical students preparing for competitive exams. Schwann cells in the PNS are responsible for myelination, while oligodendrocytes in the CNS perform this function. This distinction is essential for distinguishing between the two systems' structural and functional properties, enabling competent diagnosis and treatment of neurological disorders affecting these components.