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Lacy’s Dry Run

How the Body Maintains Water Balance


Author(s)

Ann L. Parkinson
School of Health and Sport Sciences
University of the Sunshine Coast
aparkins@usc.edu.au
Nicole B. Reinke
School of Health and Sport Sciences
University of the Sunshine Coast
nreinke@usc.edu.au

Abstract

This interrupted case study in renal physiology and water balance follows the story of "Lacy," a star athlete, who makes poor fluid intake choices for the duration of a track and field day. Lacy notices changes in the volume and appearance of her urine as the day progresses, and eventually succumbs to suspected dehydration. Students work through questions about general body water inputs and outputs, the structure of the nephron and the locations within the nephron where water and sodium ion reabsorption take place. The hormonal control of water and sodium ion reabsorption by vasopressin (antidiuretic hormone) and aldosterone are also deliberated. Students then consider how nephron function is affected by the consumption of caffeine and the implications of body water imbalances on the functioning of the cardiovascular system. This case was developed for use in an upper-level human physiology course taken over two semesters and could be adapted for a lower-level physiology problem-based learning tutorial or extended for a pathophysiology course.


Objectives

  • Describe the major sources of water input and output in the human body.
  • Describe the mechanisms of water loss from the human body.
  • Describe the reabsorption of water and sodium ions in the nephron.
  • Describe the effects of caffeine on nephron function.
  • Explain some of the consequences of an imbalance of body water.
  • Describe the relationship between body fluid and blood pressure.
  • Outline the mechanisms by which water is absorbed in the small intestine.

Keywords

Renal; nephron; water balance; vasopressin; aldosterone; blood pressure; water loss; dehydration; rehydration; caffeine; sports drink

Topical Areas

N/A

Educational Level

Undergraduate lower division, Undergraduate upper division

Format

PDF

Type / Methods

Discussion, Interrupted

Language

English

Subject Headings

Physiology  |   Medicine (General)  |   Sports Science  |  


Date Posted

11/1/2019

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