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The critical role of logarithmic transformation in Nernstian equilibrium potential calculations

Sawyer, Jemima E.R.; Hennebry, James E.; Revill, Alexander; Brown, Angus M.

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Authors

Jemima E.R. Sawyer

James E. Hennebry

Alexander Revill

Angus M. Brown



Abstract

The membrane potential, arising from uneven distribution of ions across cell membranes containing selectively permeable ion channels, is of fundamental importance to cell signaling. The necessity of maintaining the membrane potential may be appreciated by expressing Ohm’s law as current = voltage/resistance and recognizing that no current flows when voltage = 0, i.e., transmembrane voltage gradients, created by uneven transmembrane ion concentrations, are an absolute requirement for the generation of currents that precipitate the action and synaptic potentials that consume >80% of the brain’s energy budget and underlie the electrical activity that defines brain function. The concept of the equilibrium potential is vital to understanding the origins of the membrane potential. The equilibrium potential defines a potential at which there is no net transmembrane ion flux, where the work created by the concentration gradient is balanced by the transmembrane voltage difference, and derives from a relationship describing the work done by the diffusion of ions down a concentration gradient. The Nernst equation predicts the equilibrium potential and, as such, is fundamental to understanding the interplay between transmembrane ion concentrations and equilibrium potentials. Logarithmic transformation of the ratio of internal and external ion concentrations lies at the heart of the Nernst equation, but most undergraduate neuroscience students have little understanding of the logarithmic function. To compound this, no current undergraduate neuroscience textbooks describe the effect of logarithmic transformation in appreciable detail, leaving the majority of students with little insight into how ion concentrations determine, or how ion perturbations alter, the membrane potential.

Citation

Sawyer, J. E., Hennebry, J. E., Revill, A., & Brown, A. M. (2017). The critical role of logarithmic transformation in Nernstian equilibrium potential calculations. Advances in Physiology Education, 41(2), https://doi.org/10.1152/advan.00166.2016

Journal Article Type Article
Acceptance Date Jan 20, 2017
Publication Date Jun 1, 2017
Deposit Date Apr 27, 2017
Publicly Available Date Jun 1, 2017
Journal Advances in Physiology Education
Print ISSN 1043-4046
Electronic ISSN 1522-1229
Publisher American Physiological Society
Peer Reviewed Peer Reviewed
Volume 41
Issue 2
DOI https://doi.org/10.1152/advan.00166.2016
Public URL https://nottingham-repository.worktribe.com/output/863413
Publisher URL http://advan.physiology.org/content/41/2/231
Contract Date Apr 27, 2017

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