Why the amplitude of first compound action potential is larger than the second action potential?

The amplitude of the first compound action potential (CAP) is larger than that of the second due to the recruitment of more axons during the initial stimulation. In the first CAP, a greater number of nerve fibers are activated, producing a larger overall signal. Subsequent stimulation may activate fewer fibers or those that are less responsive, resulting in a smaller amplitude for the second action potential. Additionally, factors such as fatigue or changes in ion channel availability can also contribute to the reduced amplitude in subsequent responses.