Q.Which of the following statements is wrong regarding conduction of nerve impulse?
a. In a resting neuron, the axonal membrane is more permeable to K+ ions and nearly impermeable to Na+ ions.
b. Fluid outside the axon has a high concentration of Na+ ions and low concentration of K+, in a resting neuron.
c. Ionic gradients are maintained by Na+ K+ pumps across the resting membrane, which transport 3Na ions outwards for 2K+ into the cell.
d. A neuron is polarized only when the outer surface of the axonal membrane possess a negative a charge and its inner surface is positively charged.

A nerve impulse is a travelling electrical signal made possible by an unequal distribution of ions across the axolemma — high K+ and negatively charged proteins inside the axon, high Na+ outside — actively maintained by the ATP-driven sodium-potassium pump (3 Na+ out for every 2 K+ in). At rest, the membrane is far more permeable to K+ than Na+, so the inside stays negative relative to the outside (typically around -70 mV); this baseline is the resting potential, and the membrane is described as polarized. A strong enough stimulus opens voltage-gated Na+ channels, letting Na+ rush in and flip the membrane's charge — depolarization — and once this reaches the threshold potential (~-55 mV) the neuron fires completely (the all-or-none principle), spiking to roughly +45 mV. The Na+ gate then closes and the K+ gate opens, letting K+ flow back out and pulling the potential back down — repolarization — and because the K+ gates ('lazy gates') close slowly, the potential often b …