Which of these processes occur during repolarisation of nerve fibre? Open  channel Closed  channel Closed  channel Open  channel
a)	II and IV	b)	I and III	c)	II and III	d)	I and II

(a)

In neurons, the restoration of resting potential is called repolarization. After depolarization, with the increase of sodium ions inside the nerve fibre, the membrane becomes less permeable to  and more to . the  channels of axon membrane close and  channels open.  influx stops and  outflow starts until the original resting state of ionic concentration is achieved. Thus, resting potential is restored, which is called repolarization of the membrane. Until repolarization occurs, neuron cannot conduct another impulse. The time taken for this restoration is called refractory period.