The correct option is Schwann cells.
Explanation
The nervous system comprises neurons and neuroglial (glial) cells. Glial cells provide support, nutrition, and protection to neurons. A critical function of specific glial cells is myelination, the formation of a lipid-rich sheath around axons to insulate them and accelerate the transmission of electrical impulses.
Option Analysis
- Schwann cells is Correct: Schwann cells are the specific glial cells found in the Peripheral Nervous System (PNS). They wrap around the axons of neurons in the PNS to form the myelin sheath. Each Schwann cell myelinates only a single segment of a single axon.
- Oligodendrocytes is Incorrect: Oligodendrocytes are responsible for forming the myelin sheath in the Central Nervous System (CNS) (brain and spinal cord). Unlike Schwann cells, a single oligodendrocyte can extend its processes to myelinate segments of multiple axons simultaneously.
- Microglia is Incorrect: Microglia are specialized immune cells (macrophages) located in the CNS. They perform phagocytosis, clearing cellular debris and pathogens, and are not involved in myelination.
- Ependyma is Incorrect: Ependymal cells line the ventricles of the brain and the central canal of the spinal cord. They are involved in the production and circulation of cerebrospinal fluid (CSF).
Key Takeaway
The primary distinction in myelination lies in the location: Schwann cells myelinate axons in the Peripheral Nervous System (PNS), whereas Oligodendrocytes myelinate axons in the Central Nervous System (CNS).