What is the diameter range of A fibers?

What is the diameter range of A fibers?

• A. 0.4-1.2 um
• B. 2-6 um
• C. 1-4 um
• D. 4-8 um

Answer: (C)

Nerve fiber size and myelination determine how signals travel and how local anesthetics affect them. Among myelinated fibers, the A category spans a range from small to large diameters. The smallest members of this group are the A-delta fibers, which are relatively narrow yet still myelinated and thus conduct impulses faster than unmyelinated fibers but slower than the largest myelinated fibers. Therefore, when you’re asked for the diameter range associated with A fibers, the best match is the smaller end of the myelinated-fiber spectrum, corresponding to these small A fibers. The other ranges point to either much larger myelinated fibers (which handle different functions) or to unmyelinated fibers, so they don’t fit the typical A-fiber diameter description.

Nerve fiber size and myelination determine how signals travel and how local anesthetics affect them. Among myelinated fibers, the A category spans a range from small to large diameters. The smallest members of this group are the A-delta fibers, which are relatively narrow yet still myelinated and thus conduct impulses faster than unmyelinated fibers but slower than the largest myelinated fibers. Therefore, when you’re asked for the diameter range associated with A fibers, the best match is the smaller end of the myelinated-fiber spectrum, corresponding to these small A fibers. The other ranges point to either much larger myelinated fibers (which handle different functions) or to unmyelinated fibers, so they don’t fit the typical A-fiber diameter description.