Please ans this and explain what is meant by "reversal of resting membrane polarity".

The correct option is (1). 

The resting potential membrane is the state of a neuron when there is no conduction of nerve impulse. 

The Na⁺/K⁺ Pump plays an important role in maintaining resting potential. This can be explained as:

At the resting state of a neuron:

• Axonal membrane is more permeable to K⁺ and nearly impermeable to Na⁺.
• It is impermeable to negatively charged proteins present inside the axoplasm. Thus, it does not let them go out.​ As a result, the axoplasm has more concentration of K⁺ and negatively charged proteins, and less concentration of Na⁺. This creates a concentration gradient.
• Gradient is maintained by the Sodium-Potassium Pump which pumps 3Na⁺ out and 2K⁺ in.
• Hence, the outer surface of the membrane possesses a positive charge and the inner surface possesses a negative charge. This potential difference is called Resting Potential.

When a stimulus is applied at a particular site (say site A), that site becomes freely permeable to the influx of Na⁺; hence, the polarity at that site is reversed.

The membrane is now depolarised, and the potential difference across the site is called Action Potential.

Hope this clears your doubt.
Regards.
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