During the conduction of a nerve impulse along a neuron,what is the nature of the electrical charge on the inner side of the plasma membrane?

$A$: Presence of myelin sheath increases the rate of conduction of nerve impulse.
$R$: Ionic channels are absent in the area covered by myelin sheath; therefore,depolarization occurs only at the nodes of Ranvier,resulting in saltatory or jumping conduction.

Which has the highest speed of nerve impulse?

Select the correct option for the sodium-potassium pump.

Consider the statements as True/False:
$I$. The axoplasm inside the axon contains a high concentration of $K^{+}$ and negatively charged proteins.
$II$. The axoplasm inside the axon contains a low concentration of $Na^{+}$.
$III$. The fluid outside the axon contains a low concentration of $K^{+}$.
$IV$. The fluid outside the axon contains a high concentration of $Mg^{++}$ and negatively charged proteins.
The correct option is:

On application of a stimulus on the axonal membrane,