Which fiber type has a diameter range of 1-4 um?

Which fiber type has a diameter range of 1-4 um?

• A. A fibers
• B. C fibers
• C. B fibers
• D. D fibers

Answer: (A)

Diameter and myelination determine how fast a nerve fiber conducts impulses: larger, myelinated fibers carry signals quickly, while small or unmyelinated fibers conduct slowly. The 1–4 micrometer range fits the thinly myelinated subset of the A-type fibers, known as A-delta fibers. These fibers are small yet myelinated, and they carry fast pain and temperature signals—faster than unmyelinated C fibers but slower than the largest myelinated A fibers. So the 1–4 μm diameter range points to A-delta fibers within the A group. C fibers are unmyelinated and slower, and B fibers are myelinated but typically smaller or of a different functional class, not matched to this specific diameter window.

Diameter and myelination determine how fast a nerve fiber conducts impulses: larger, myelinated fibers carry signals quickly, while small or unmyelinated fibers conduct slowly. The 1–4 micrometer range fits the thinly myelinated subset of the A-type fibers, known as A-delta fibers. These fibers are small yet myelinated, and they carry fast pain and temperature signals—faster than unmyelinated C fibers but slower than the largest myelinated A fibers. So the 1–4 μm diameter range points to A-delta fibers within the A group. C fibers are unmyelinated and slower, and B fibers are myelinated but typically smaller or of a different functional class, not matched to this specific diameter window.