<prompt> If refractory period of nerve is 12500th of a second, what can be the maximum frequency of excitation of the nerve?100 timessec250 timessec2000 timessec2500 timessec  <response>: Refractory period is that time period after the first stimulus during which the nerve is refractory to another stimulus. Hence, maximum frequency of excitation can be 2500 times in a second, as each next stimulus can excite the nerve if applied immediately at the end of the refractory period 12500th of a second. 