PNS Neuroglia Include Schwann Cells

Schwann cells are the primary myelinating glial cells in the peripheral nervous system (PNS). The correct answer to the multiple-choice question is 2. Schwann cells.

Correct Answer

Schwann cells myelinate axons in the PNS, providing insulation for rapid nerve impulse conduction, aiding regeneration, and secreting neurotrophic factors. They derive from neural crest cells and wrap around multiple axonal segments, unlike CNS counterparts.

Option Explanations

1. Astrocytes (Incorrect)

Astrocytes are star-shaped glial cells exclusive to the central nervous system (CNS), where they support the blood-brain barrier, regulate ions, and modulate synapses. They do not occur in the PNS.

2. Schwann Cells (Correct)

Found throughout PNS nerves, Schwann cells form myelin sheaths around peripheral axons, perform phagocytosis during injury, and guide axonal regrowth. They also include non-myelinating types that envelop multiple unmyelinated axons.

3. Oligodendrocytes (Incorrect)

Oligodendrocytes myelinate multiple CNS axons simultaneously and are confined to the brain and spinal cord. PNS myelination is handled solely by Schwann cells, not oligodendrocytes.

4. Ependymal Cells (Incorrect)

Ependymal cells line the ventricles of the brain and central canal of the spinal cord in the CNS, producing and circulating cerebrospinal fluid. They have no role or presence in the PNS.