Period of depolarization of the neuron membrane during which it cannot respond to a second stimulus

The answer is absolute refractory period. The absolute refractory period defines the time of latency that happens after a nerve has been fired. Enduring 1-2 minutes throughout this stage the neuron cannot be roused no matter how tough the stimulus is. It is fundamentally renewing itself in order to be capable to fire again. The NA+ stations in the neuron are neutralized throughout the absolute refractory period and are not capable to react to any stimulus. Succeeding the absolute refractory period is the relative refractory period which is longer in extent and is when the neuron is capable to react to a stimulus but desires a stronger than normal stimulus in order to do so. 

Ithink that its like 15 mph.