Which statement about myelination in the peripheral nervous system is true?

Which statement about myelination in the peripheral nervous system is true?

• A. All peripheral nerve fibers are myelinated.
• B. Pain fibers are heavily myelinated to speed signaling.
• C. Only nerves that connect muscles are myelinated.
• D. Some peripheral fibers are myelinated to speed transmission, while others are unmyelinated depending on function.

Answer: (D)

In the peripheral nervous system, myelination varies among axons. Some fibers are wrapped in myelin by Schwann cells, which speeds signal transmission, while others remain unmyelinated because of their smaller size or different functional needs. Myelin enables saltatory conduction, where electrical impulses jump from one node of Ranvier to the next, dramatically increasing speed and reducing energy use for action potentials along those insulated segments. Pain signaling isn’t uniformly fast or uniform in myelination. There are fast, lightly myelinated A-delta fibers and slower, unmyelinated C fibers, so pain transmission isn’t simply “heavily myelinated.” Likewise, many nerve fibers that do not connect to muscles can be myelinated or unmyelinated depending on their role. So the accurate statement is that some peripheral fibers are myelinated to speed transmission, while others are unmyelinated depending on function.

In the peripheral nervous system, myelination varies among axons. Some fibers are wrapped in myelin by Schwann cells, which speeds signal transmission, while others remain unmyelinated because of their smaller size or different functional needs. Myelin enables saltatory conduction, where electrical impulses jump from one node of Ranvier to the next, dramatically increasing speed and reducing energy use for action potentials along those insulated segments.

Pain signaling isn’t uniformly fast or uniform in myelination. There are fast, lightly myelinated A-delta fibers and slower, unmyelinated C fibers, so pain transmission isn’t simply “heavily myelinated.” Likewise, many nerve fibers that do not connect to muscles can be myelinated or unmyelinated depending on their role.

So the accurate statement is that some peripheral fibers are myelinated to speed transmission, while others are unmyelinated depending on function.