The Nernst equation is key to understanding the electrophysiology of the cell membrane and the pathophysiology of K+ imbalances (i.e., hyperkalemia and hypokalemia). However, in our experience teaching medical students over the years, many students struggle to make connections between a brief introduction of the Nernst equation and its clinical application to K+ imbalances. This article aims to connect the introduction of the equation to its clinical application to understand K+ imbalances using six logical steps with detailed visual illustrations that make the connection explicit and cohesive. In addition, we highlight a few common areas related to the six steps that are often overlooked by both teachers and students. Students who are able to thoroughly demonstrate an understanding of all the six steps highlighted in this article will achieve mastery of this topic.NEW & NOTEWORTHY This article fills the gaps in teaching about the Nernst equation, which is important in medical physiology. Six logical steps are presented that connect the introduction of the equation to its clinical applications to hyperkalemia and hypokalemia, two conditions that can be life-threatening if left untreated. Only when students know how to apply the equation will their learning transition from surface to mastery.
Keywords: Nernst equation; chemical gradient; equilibrium potential; hyperkalemia; hypokalemia.