During refractory period, ____

The refractory period of a neuron is the time in which a nerve cell is unable to fire an action potential (nerve impulse).  

• For a few milliseconds after the initiation of an action potential, it is impossible to trigger a second action potential. 
• This period is known as the absolute refractory period. 
• This period coincides with the period during which the voltage-gated Na⁺ channels are either activated or inactivated (depolarising and repolarising phases).