What is the diameter range for A fibers?

What is the diameter range for A fibers?

• A. 1-22 μm
• B. 100-200 μm
• C. 0.1-0.5 μm
• D. 50-80 μm

Answer: (A)

A fibers are the large, heavily myelinated nerve fibers, which gives them the fastest conduction among peripheral fibers. Their diameter spans roughly 1 to 22 micrometers, covering the Aα, Aβ, and Aδ subtypes. That broad range reflects the different speeds within this group, from the very fast Aα and Aβ to the somewhat slower Aδ, but all remain within the large, myelinated category. The other options fall outside what peripheral myelinated fibers achieve: 100–200 μm is too large for any peripheral fiber, 0.1–0.5 μm corresponds to unmyelinated C fibers, and 50–80 μm is not representative of the typical diameters in this category.

A fibers are the large, heavily myelinated nerve fibers, which gives them the fastest conduction among peripheral fibers. Their diameter spans roughly 1 to 22 micrometers, covering the Aα, Aβ, and Aδ subtypes. That broad range reflects the different speeds within this group, from the very fast Aα and Aβ to the somewhat slower Aδ, but all remain within the large, myelinated category. The other options fall outside what peripheral myelinated fibers achieve: 100–200 μm is too large for any peripheral fiber, 0.1–0.5 μm corresponds to unmyelinated C fibers, and 50–80 μm is not representative of the typical diameters in this category.