In the resting stage of a neuron,the concentration gradient is generated due to:

Which of the following events occur during the repolarization of a nerve fiber?

Which of these processes occur during repolarisation of nerve fibre?
$(I)$. Open $Na^+$ channel
$(II)$. Closed $Na^+$ channel
$(III)$. Closed $K^+$ channel
$(IV)$. Open $K^+$ channel

Select the correct sequence of statements regarding the conduction of a nerve impulse and select the correct option given below.
$i.$ Rapid influx of $Na^{+}$ inside the axon.
$ii.$ $Na^{+}$ gates are closed and $K^{+}$ gates open after the refractory period.
$iii.$ Intracellular fluid is electronegative and the potential difference is $-70 \ mV$.
$iv.$ Extracellular fluid becomes electronegative.
$v.$ Disturbance to the resting potential.

Resting membrane potential is maintained by

The propagation of an action potential during nerve impulse conduction is made possible by the movement of: