What is resting potential? How does the conduction of a nerve impulse take place?

(N/A) Resting potential is the electrical potential difference across the resting axonal membrane.
Neurons are excitable cells because their membranes are in a polarised state.
Different types of ion channels are present on the neural membrane,which are selectively permeable to different ions.
When a neuron is not conducting any impulse (resting state),the axonal membrane is comparatively more permeable to $K^{+}$ and nearly impermeable to $Na^{+}$.
Similarly,the membrane is impermeable to negatively charged proteins present in the axoplasm.
The axoplasm inside the axon contains a high concentration of $K^{+}$ and negatively charged proteins,and a low concentration of $Na^{+}$.
In contrast,outside the axon,there is a low concentration of $K^{+}$ and a high concentration of $Na^{+}$,forming a concentration gradient.
These ionic gradients across the resting membrane are maintained by the active transport of $3 Na^{+}$ outwards and $2 K^{+}$ inwards by the $Na^{+}-K^{+}$ pump.
As a result,the outer surface of the axonal membrane is positively charged and its inner surface becomes negatively charged; thus,it is polarised.
When a stimulus is applied at point $A$ on the polarised membrane,it becomes freely permeable to $Na^{+}$. The influx of $Na^{+}$ causes a reversal of polarity (depolarisation),where the outer membrane becomes negatively charged and the inner side becomes positively charged.
The electrical potential difference across the plasma membrane at the site $A$ is called the action potential,which is termed a nerve impulse.
At sites immediately ahead (e.g.,site $B$),the axon membrane still has a positive charge on the outer surface and a negative charge on its inner surface.
As a result,a current flows on the inner surface from site $A$ to site $B$,and on the outer surface,current flows from site $B$ to site $A$ to complete the circuit.
Consequently,the polarity at site $B$ is reversed,and an action potential is generated there.
This sequence is repeated along the length of the axon,conducting the impulse.
The stimulus-induced permeability to $Na^{+}$ is short-lived and is quickly followed by a rise in permeability to $K^{+}$. Within a fraction of a second,$K^{+}$ diffuses outside,restoring the resting potential of the membrane.