- 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 physico-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 Nα+ 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 Nα+ and K+ ions across the axonal membrane required for the RMP, is dependent on the activity of Nα+, K+-ATPase.
(E) Impermeable proteins in the axoplasm do not affect the distribution of diffusible ions across the axonal membrane which is required for the RMP.
(F) Nα+, K+-ATPase pump in the axonal membrane Which is essential for the RMP, is not electrogenic. Choose all correct statements from the following options:
(1) A,B and C only (2) B, C and D only
(3) C, D and E only (4) D, E and F only
Introduction
The resting membrane potential (RMP) of approximately -70 mV in neurons is a fundamental electrochemical state critical for action potential generation and nerve impulse conduction. This stable voltage difference across the neuronal membrane results from complex interactions among ionic concentration gradients, membrane permeability, and energy-dependent ion pumps. Here, we analyze the core physico-chemical and biological factors responsible for establishing and maintaining the RMP based on proposed statements.
Key Principles Underpinning Resting Membrane Potential
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Ion Concentration Gradients and Unequal Distribution (Statement B)
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RMP arises from unequal distributions of diffusible ions, mainly sodium (Na⁺), potassium (K⁺), chloride (Cl⁻), and impermeant intracellular anions like proteins.wikipedia+1
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Potassium concentration is higher inside the neuron, while sodium concentration is higher outside, establishing electrical gradients across the membrane.
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Selective Permeability of Membrane to Ions (Statement C)
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The neuronal membrane is selectively permeable, with higher permeability to K⁺ at rest due to potassium leak channels.
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This permeability allows K⁺ to move out of the cell more freely than Na⁺ can enter, which contributes to a negative internal charge and hence, the negative resting potential.courses.lumenlearning+1
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Role of Sodium-Potassium ATPase Pump (Statement D)
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The Na⁺/K⁺-ATPase actively transports 3 Na⁺ ions out and 2 K⁺ ions in, maintaining the concentration gradients essential for RMP.
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This pump is energy-dependent and crucial for sustaining the ionic gradients over time.wikipedia
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Equilibrium Potential is Close to Potassium’s, Not Sodium’s (Statement A)
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Despite the presence of Na⁺, the RMP is closer to the equilibrium potential of K⁺ (~-90 mV) due to membrane permeability rather than Na⁺ (~+60 mV).
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Therefore, the statement that RMP is close to Na⁺ equilibrium potential is incorrect.
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Effect of Impermeant Intracellular Proteins (Statement E)
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Negatively charged impermeant proteins inside the neuron contribute to the charge difference and influence ion distributions, affecting RMP[^][^].
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Stating that they do not affect ion distribution is incorrect.
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Electrogenic Property of the Pump (Statement F)
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The Na⁺/K⁺ ATPase is electrogenic because it moves more positive charges out (3 Na⁺) than in (2 K⁺), contributing to the negative internal potential.derangedphysiology+1
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Evaluation of Proposed Statements
Statement Content Correctness A RMP close to Na⁺ equilibrium potential Incorrect B Unequal distribution of diffusible ions is necessary Correct C Membrane permeable to ions is necessary for RMP Correct D Na⁺/K⁺ ATPase-dependent concentration gradients required Correct E Impermeant proteins do not affect ion distribution Incorrect F Na⁺/K⁺ ATPase pump is not electrogenic Incorrect
Correct Option
The statements that accurately represent the basis of RMP are:
(2) B, C and D only
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