Velocity of conduction for A alpha fibers is
**Core Concept**
The velocity of conduction in nerve fibers is determined by the diameter of the fiber and the presence of myelination. A alpha fibers are large, myelinated fibers that are responsible for transmitting sensory and motor signals over long distances.
**Why the Correct Answer is Right**
The velocity of conduction in A alpha fibers is approximately 80-120 meters per second, which is the fastest among all nerve fibers. This is due to the presence of myelination, which allows the action potential to jump from node to node, increasing the speed of conduction. The large diameter of A alpha fibers also contributes to their fast conduction velocity.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a lower velocity than A alpha fibers. Myelinated fibers with smaller diameters, such as A beta fibers, have slower conduction velocities.
**Option B:** This option is incorrect because it is a lower velocity than A alpha fibers. Unmyelinated fibers, such as C fibers, have much slower conduction velocities.
**Option C:** This option is incorrect because it is a higher velocity than A alpha fibers. Some sources may quote velocities up to 130 meters per second, but 120 meters per second is a commonly accepted value.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the velocity of conduction in nerve fibers is directly related to the diameter of the fiber and the presence of myelination. This knowledge is crucial in understanding various neurological conditions, such as peripheral neuropathy and multiple sclerosis.
**Correct Answer:** C. 120 meters per second