What does amplitude measure in nerve conduction and sensory nerve conduction?

The amplitude in nerve conduction studies, particularly in sensory nerve action potentials (SNAP) and compound muscle action potentials (CMAP), measures the number of nerve fibers that are actively conducting the electrical impulse. A higher amplitude indicates that a greater number of fibers are contributing to the measured potential, which reflects the overall functional status of the nerve.

In sensory nerve conduction, the amplitude of the SNAP corresponds to the number of sensory fibers that respond to stimulation. Similarly, in motor nerve conduction, the amplitude of the CMAP reflects the number of motor fibers that are activated when a nerve signal is transmitted to a muscle. This measurement is crucial for diagnosing conditions that may affect nerve fiber integrity or the ability of fibers to propagate signals effectively.

The other options do not accurately represent what amplitude signifies in these contexts. Hence, option B is the correct choice as it directly relates to the quantification of the active fibers contributing to the signals being measured.