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Running Off Track

A Case Study in Renal Physiology



Co Authors:

Maria-Elena Conin
Department of Biology
Villanova University

Lea C. George
Department of Biology
Villanova University

Joshua D. Kumin
Department of Biology
Villanova University

Philip J. Stephens
Department of Biology
Villanova University
phil.stephens@villanova.edu

Abstract:

This interrupted case study follows the course of Cara, a high school athlete training for the state championships in cross country. She suffers from polycystic ovarian syndrome and her prescribed medication (spironolactone) greatly diminishes the action of aldosterone on the distal tubule and the collecting duct of kidney nephrons.  During practice her symptoms of dehydration are complicated by her medication with the result that her extracellular levels of sodium and potassium become imbalanced. As Cara's story develops, students will need to learn and explain the mechanism of aldosterone action on the kidney and her symptoms in terms of ion imbalance and membrane depolarization. This case study was written for use in a one-semester animal physiology course, which is taken by junior and senior science majors; it could also be used in an anatomy and physiology course that covers membrane potentials and the role of aldosterone in ion balance and kidney function.

Objectives:
  • Describe the signs and symptoms of dehydration.
  • Describe the action of aldosterone on P-cells in the distal tubule and the collecting duct of kidney nephrons.
  • Explain how an aldosterone receptor antagonist affects the levels of sodium and potassium in the blood.
  • Describe how an aldosterone receptor antagonist can be a diuretic.
  • Calculate the equilibrium potential for potassium using the Nernst equation.
  • Predict how an elevated extracellular level of potassium can depolarize the membrane potential.
  • Explain how membrane depolarization can induce cramping of skeletal muscles.
  • Explain how membrane depolarization can increase heart rate and produce arrhythmias.
Keywords: aldosterone; spirolactone; receptor; nephron; membrane potential; equilibrium potential; potassium; sodium; dehydration
Topical Area: N/A
Educational Level: Undergraduate lower division, Undergraduate upper division
Formats: PDF
Type/Method: Interrupted
Language: English
Subject Headings: Biology (General)   Medicine (General)   Physiology   Neuroscience  
Date Posted: 11/25/2016
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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