Transforming a Logically Coherent Countercurrent Multiplication Model into Interactive Courseware to Improve Physiology Education

Objectives: Countercurrent multiplication (CCM) remains one of the most conceptually challenging topics in renal physiology because traditional textbook explanations contain longstanding hidden logical flaws and lack operational, process-based models. This project aims to transform a cycle-by-cycle CCM model with internal logical consistency into interactive, modular teaching courseware, including narrated video instruction, visualizations, simulations, and learner guides, to enhance conceptual understanding among physiology students. It builds upon the author’s 2023 article in Advances in Physiology Education, which introduced a cycle-by-cycle CCM framework supported by mathematical modeling. Hypothesis: Interactive courseware grounded in the revised CCM framework and supported by adjustable mathematical simulations will improve learner comprehension, reasoning accuracy, and retention compared with traditional instructional approaches. Methods: By adding a historically missing logical link in conventional explanations of CCM that has long prevented a fully coherent mechanistic understanding of corticopapillary osmotic gradient (OGISF) formation, instructional design is organized around a logically coherent and complete, cycle-by-cycle explanatory framework. Interactive simulations adapted from the original Excel-based mathematical models (a supplemental file to author’s 2023 article) allow learners to manipulate key physiological parameters, including the transepithelial osmolarity gradient across the thick ascending limb, initial intra- and extraluminal osmolarity, cycle number, and antidiuretic hormone (ADH) status. By directly visualizing osmolarity changes across cycles, learners can examine how NKCC2-mediated transport governs the OGISF formation. The materials are being prepared for live classroom demonstration, self-directed study, and small-group discussion, followed by pilot implementation and iterative refinement. Planned pilot testing will assess usability, conceptual clarity, and the effectiveness of interactive visualization in promoting mechanistic understanding of the revised CCM framework. Results will inform iterative refinement prior to broader dissemination. Results/Instructional Architecture: The courseware is structured into four conceptual modules: (1) physiological conditions required for OGISF formation, with explicit distinction between passive factors and active driving force; (2) the emergence of OGISF from an initially uniform state; (3) progressive amplification of OGISF across repeated cycles; and (4) the transient nature of CCM and why the process cannot operate continuously. Conclusions: Translating the revised CCM framework into interactive courseware shows strong potential to resolve persistent instructional challenges and enhance conceptual mastery in renal physiology. By providing a scalable, openly accessible instructional tool, this work invites broader collaboration and continued refinement within the physiology teaching community. Funding: This work is supported by the 2025 APS Teaching Career Enhancement Award (TCEA). This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.