Answer: Option B
:
B
The Refractory Period, after an action potential is the period during which the neuron resists the production of another action potential;
Two types of Refractory Periods are seen :
1. Absolute Refractory Period (1-2 m/sec) : The voltage gated sodium channels are closed by the inactivation gates, and not the voltage regulated gate, and therefore do not open even to high levels of depolarization. Therefore action potential will not fire even at a very high stimulus.
2. Relative Refractory Period : In this period the inactivation gates of voltage gated Na+ channels are open, but the membrane is hyperpolarized after an action potential and will require a higher than normal stimulus, for an action potential to fire.
The incorrect statement here is ‘Postsynapticmembrane will not depolarize’. The initial depolarization of a membrane when a stimulus arrives is due to chemical gated sodium channels. These channels open even during the refractory period, therefore a membrane will depolarize even during the refractory period.