Explanation

In a resting nerve fibre, sodium ions predominates in the extracellular fluid, whereas potassium ions predominates in the intracellular fluid. The plasma membrane is electrically positive outside and negative inside. This difference is called potential difference. In neurons, the average resting membrane potential value is -70 mV. During depolarisation, the potential inside the membrane change from -70 mV to +30 mV. Resting potential is generally between -70 mV to -90 mV.