Ch. 25 Fluid, Electrolyte, and Acid-Base Homeostasis

Amerman3rd EditionHuman Anatomy & PhysiologyISBN: 9780138247201, 9780138247928, 9780138201814Not the one you use?Change textbook

Amerman 3rd Edition

Ch. 25 Fluid, Electrolyte, and Acid-Base Homeostasis

Problem L2.2

Chapter 25, Problem L2.2

A woman begins a diet and exercise regimen and loses 30 lb. Will her total body water increase, decrease, or stay the same? Why?

Verified step by step guidance

Understand that total body water (TBW) is closely related to body composition, particularly the proportion of lean body mass (muscle) and fat mass. Muscle tissue contains more water (approximately 75%) compared to fat tissue (approximately 10%).

Recognize that when a person loses weight, the composition of the weight loss matters. If the weight loss is primarily from fat, the reduction in total body water will be minimal because fat tissue contains relatively little water.

Consider that if the weight loss includes a significant amount of muscle mass (e.g., due to inadequate protein intake or excessive calorie restriction), the total body water will decrease more significantly because muscle tissue is water-rich.

Evaluate the role of hydration and exercise. If the woman maintains or increases her muscle mass through resistance training and proper hydration during her regimen, her total body water might stay the same or even increase despite the weight loss.

Conclude that the change in total body water depends on the balance of fat loss versus muscle loss. If the weight loss is primarily fat, TBW will decrease slightly. If muscle mass is preserved or increased, TBW may stay the same or increase.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Total Body Water (TBW)

Total Body Water refers to the amount of fluid in the body, which is essential for various physiological functions. It constitutes a significant portion of body weight and is influenced by factors such as age, sex, and body composition. Understanding TBW is crucial for assessing hydration status and the effects of weight loss on body composition.

Body Composition Changes

Body composition changes during weight loss can affect the distribution of water in the body. When a person loses weight, especially through dieting, they often lose both fat and lean mass, which can alter the proportion of water in the body. This change can lead to a decrease in total body water, particularly if the weight loss is rapid or involves significant loss of muscle mass.

Hydration and Weight Loss

Hydration plays a critical role in weight loss and overall health. During a weight loss regimen, individuals may experience changes in fluid balance due to dietary restrictions and increased physical activity. If the diet is low in carbohydrates, for example, glycogen stores deplete, leading to a loss of water weight. Therefore, understanding how hydration interacts with weight loss is essential for predicting changes in total body water.

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Related Practice

Textbook Question

Elise Anderson is a 6-year-old girl who presents to the emergency department with a history of vomiting for the past 3 days. The nurse notices that her respiratory rate is abnormally low. What is the likely reason for this change in ventilation? Predict what Elise's arterial blood gas values would show.

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Textbook Question

Your friend argues that all water conducts electricity, regardless of what it contains. You prepare three liquids to test this hypothesis: one with distilled water (with no solutes, only water molecules), one with 5% glucose in distilled water, and one with 5% sodium chloride in water. Which of these solutions, if any, will conduct an electric current? Explain.

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Textbook Question

Explain how the amount of water in the body affects the concentration of ions and solutes in the ECF.

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Textbook Question

Diabetic ketoacidosis is characterized by an increased level of ketone bodies, which causes metabolic acidosis. A patient in diabetic ketoacidosis will have an altered rate of ventilation. Will the patient be hyperventilating or hypoventilating? How will a change in the rate and depth of ventilation compensate for an acidosis that is metabolic in nature?

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Textbook Question

What happens to the concentration of sodium ions in the ECF if you consume a large amount of salt without consuming any water? How will this affect the osmotic pressure of the ECF? Why could this lead to an elevation in blood pressure?

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Textbook Question

What happens to the pH of a solution when hydrogen ions are added?

a. The pH increases.

b. The pH decreases.

c. The pH does not change.

d. The pH does not measure hydrogen ion concentration.

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