A potential difference of about -70 mV between inside and outside of a single axonal membrane in resting condition may be recorded by suitable electrodes and amplifier. The pyresico-chemical and biological basis of the origin of this resting membrane potential (RMP) are suggested below:

A. The RMP is close to the equilibrium of Na⁺ ion.
B. There must be an unequal distribution of diffusible ions across the axonal membrane for the RMP.
C. The axonal membrane must be permeable to one or more species of ions for the RMP.
D. The concentration gradient of Na⁺/K⁺ ions across the axonal membrane required for the RMP, is dependent on the activity of Na⁺/K⁺ ATPase.
E. Impermeable proteins in the axoplasm do not affect the distribution of diffusible ion acoss the axonal membrane which is required for the RMP.
F. Na⁺, K⁺-ATPase pump in the axonal membrane which is essential for the RMP, is not electrogenic.

Choose all correct statements from the following options:

Correct option is B

Explanation-

(A) The RMP is close to the equilibrium of Na⁺ ion - INCORRECT
The RMP (~ -70 mV) is much closer to the equilibrium potential of K⁺ (~ -90 mV), not Na⁺. Sodium has a positive equilibrium potential (~+60 mV), and Na⁺ tends to flow inward.

(B) There must be an unequal distribution of diffusible ions across the axonal membrane for the RMP - CORRECT
The RMP arises due to unequal distribution of Na⁺, K⁺, Cl⁻ and impermeant anions across the membrane and their selective permeability. This ionic asymmetry is fundamental for generating membrane potential.

(C) The axonal membrane must be permeable to one or more species of ions for the RMP  - CORRECT
The membrane is selectively permeable, mostly to K⁺ at rest. This selective permeability is essential for the RMP to exist.

(D) The concentration gradient of Na⁺ and K⁺ ions across the axonal membrane required for the RMP, is dependent on the activity of Na⁺, K⁺-ATPase  - CORRECT
The Na⁺/K⁺ pump maintains the Na⁺ and K⁺ gradients by actively transporting 3 Na⁺ out and 2 K⁺ in, which is essential for sustaining the RMP over time.

(E) Impermeable proteins in the axoplasm do not affect the distribution of diffusible ions across the axonal membrane which is required for the RMP - INCORRECT
Impermeable negatively charged proteins inside the axon contribute to the RMP by affecting the overall charge balance and distribution of diffusible ions.

(F) Na⁺, K⁺-ATPase pump in the axonal membrane which is essential for the RMP, is not electrogenic - INCORRECT
The Na⁺/K⁺ pump is electrogenic, because it moves 3 Na⁺ out for every 2 K⁺ in, contributing directly to the negativity of the RMP.

Correct Combination:
Option b: B, C and D only
This is the correct answer as these are the only accurate statements based on the physiology of the resting membrane potential.