Negative Feedback System and Red Blood Cell Physiology, Exams of Human Physiology

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Gabi N. Waite

Maria Sheakley

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Acquisition Editor: Delia K. DeTurris Managing Editor: Kenneth Schubach Director, Editorial Services: Mary Jo Casey Production Editor: Kenny Chumbley In-House Production Editor: Naamah Schwartz International Production Director: Andreas Schabert Editorial Director: Sue Hodgson International Marketing Director: Fiona Henderson International Sales Director: Louisa Turrell Director of Institutional Sales: Adam Bernacki Senior Vice President and Chief Operating Officer: Sarah Vanderbilt President: Brian D. Scanlan

Library of Congress Cataloging-in-Publication Data

Names: Waite, Gabi Nindl, author. | Sheakley, Maria, author. Title: Medical physiology Q&A/ Gabi N. Waite, Maria Sheakley. Description: New York : Thieme, [2018] | Includes index. Identifiers: LCCN 2017024887| ISBN 9781626233843 (pbk.) | ISBN 9781626233850 (eISBN) Subjects: | MESH: Physiological Phenomena | Examina- tion Questions Classification: LCC QP40 | NLM QT 18.2 | DDC 612.0076- -dc LC record available at https://lccn.loc.gov/

Important note: Medicine is an ever-changing science undergoing continual development. Research and clini- cal experience are continually expanding our knowledge, in particular our knowledge of proper treatment and drug therapy. Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors, and publishers have made every effort to ensure that such references are in accordance with the state of knowledge at the time of production of the book. Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publish- ers in respect to any dosage instructions and forms of ap- plications stated in the book. Every user is requested to examine carefully the manufacturers’ leaflets accompa- nying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage sched- ules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released on the market. Every dosage schedule or every form of application used is entirely at the user’s own risk and responsibility. The authors and publishers request ev- ery user to report to the publishers any discrepancies or inaccuracies noticed. If errors in this work are found after publication, errata will be posted at www.thieme.com on the product description page. Some of the product names, patents, and registered de- signs referred to in this book are in fact registered trade- marks or proprietary names even though specific refer- ence to this fact is not always made in the text. Therefore, the appearance of a name without designation as propri- etary is not to be construed as a representation by the publisher that it is in the public domain.

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To my mentor and close friend, Dr. Walter Balcavage.

Gabi N. Waite

To the mentors in my life: Dr. Barbara Francois, Dr. Charles “Chuck” Seidel, and Dr. Hashim Shams.

Maria Sheakley

viii

Preface

A successful student of the medical profession is able to synthesize concepts and principles that govern a human body and apply those concepts and principles to healthy and diseased patients. This requires the ability to integrate basic and clinical science information, such as understanding how the Frank Starling principle applies to cardiac resuscitation and how gastrointestinal physiology can aid in choosing the best diet for a patient. With this book, it is our goal to provide examples of how to synthesize, integrate, and apply physiological concepts to clinical situations, in a format similar to that used in the United States Medical Licensing Examination (USMLE). Accordingly, we took examples of high-yield concepts that we provide in the classroom and turned them into challenging multiple-choice questions. This book is a valuable resource for medical students to prepare for the USMLE Step 1 exam. Additionally, it is a book that provides students of any health profession the opportunity to self-assess their level of understanding. Students who need a resource for a condensed review, after completing a medical physiology course, can focus on

easy and moderate questions. Students who need to integrate physiological principles with their new understanding of pathology, pharmacology, or other medical topics can select moderate and difficult questions. Nursing and allied health students, who need to perform at a higher level in their area of expertise, will study moderate and difficult questions to prepare for their discipline- specific certifying exams. Even residents and professionals will benefit from a refresher in the mechanistic understanding of medicine. With the ever-expanding pool of medical knowledge, we see this book as an ongoing project that will continually be revised and updated based on scientific discovery and audience feedback. In this aspect, this book contributes to the new era of electronic publishing, where continuous improvement becomes a necessary reality. We welcome feedback, and look forward to hearing about the ways in which this book is used by aspiring and established medical professionals.

Gabi N. Waite, PhD Maria Sheakley, PhD

Acknowledgments

We gratefully acknowledge a multitude of colleagues who reviewed materials and answered questions, including David B. Averill, PhD (Geisinger Commonwealth), Roy W. Geib, PhD (Indiana University), David R. Riddle, PhD (Western Michigan University School of Medicine), Dr. Hashim Shams, MD, PhD (Ross University), and Brian Wilcox, MD, PhD (Geisinger Commonwealth). We are grateful for guidance and support from the entire Thieme staff and for their

remarkable editorial and production work. A special thanks to Delia DeTurris (acquisitions), Kenny Chumbley (production), and Kenneth Schubach (management) for their continued help and encouragement throughout the process. Last, but not least, we are thankful to our wonderful husbands, parents, friends, colleagues, and pets who deserved more attention but accepted our determination to meet the next deadline. Thank you!

ix

How to Use This Series

Question Difficulty Key Green Box = Easy question Yellow Box = Medium question Red Box = Hard question

Difficulty Level Icon In general, an easy question requires only a diagnosis based upon the question stem. A medium question requires not just the diagnosis of the condition based upon the question stem, but knowledge about that diagnosis so as to answer a question about it. Hard questions are a combination of medium questions with less commonly known material about the diagnosis.

Chapter Head

Section Header

Question

Stem

Answer Options

Chapter 1

Cellular Physiology

LEARNING OBJECTIVES

▶ Explain the general physiology of the cellular membrane, including diffusion, membrane transport, intracellular signaling, and feedback. ▶ Discuss the physiology of osmosis, tonicity, body fl uid compartment, Starling forces, and edema formation. ▶ Discuss the ion channels of the cell membrane and their role in membrane potentials and excitation. Describe the neuronal action potential.

1 Cellular Physiology

2

4. The plasma membrane is made up of a lipid bilayer, which determines the ability of substances to move in and out of the cell. Which of the follow- ing substances are lipid soluble and water soluble, respectively?

Lipid soluble Water soluble A. CO 2 and O 2 Na+^ and Glucose B. CO 2 and O 2 K+^ and Steroid hormones C. CO 2 and O 2 Cl-^ and Steroid hormones D. O 2 and Glucose Na +^ and K + E. O 2 and Glucose K +^ and CO 2 F. O 2 and Glucose Cl-^ and Na +

5. The permeability of a solute across a lipid bilayer membrane is based on the solute’s molecular radius, the oil/water partition coefficient, and the mem- brane’s thickness. Based on these factors, which of the following examples has the highest permeability?

Molecular radius

Oil/water partition coefficient

Membrane thickness

A. ↑ ↑ ↑

B. ↑ ↓ ↓

C. ↑ ↑ ↓

D. ↓ ↓ ↑

E. ↓ ↓ ↓

F. ↓ ↑ ↓

Questions 6 to 8

Five different dialysis bags, which are permeable to water but impermeable to glucose, are filled with five different glucose solutions. The bags are placed in different beakers containing a 0.5M glucose solu- tion for 80 minutes, and the mass of each bag is mea- sured at regular intervals. The results are recorded on the graph.

1.1 Questions

Easy Medium Hard

1. The provided images show ionic distribution of potassium (K +), chloride (Cl–) and sodium (Na+) across cell membranes. The concentration of each ion is represented by the size of its label, where a larger label indicates a higher concentration. Which image correctly represents the distribution of K+, Cl–, and Na +^ across a typical living cell membrane?

A. A

B. B

C. C

D. D

2. Normal cell function is dependent on fluidity of the cell membrane. An increase in which of the following characteristics of a cell membrane will increase membrane fluidity? A. Body cold stress B. Integral membrane protein content C. Peripheral membrane protein content D. Saturated phospholipid content E. Unsaturated phospholipid content 3. Which of the following best depicts the effect of cholesterol on membrane fluidity at higher and lower temperatures?

Effect of choles- terol at higher temperatures

Effect of choles- terol at lower temperatures A. Increase Increase B. Increase Decrease C. Increase No change D. Decrease Increase E. Decrease Decrease F. Decrease No change

a

c

b

d

1 Cellular Physiology

4

14. A 40-year-old man presents to his primary care physician with a 2-month history of intermit- tent upper abdominal pain shortly after eating. He is referred to a specialist, and upper gastrointestinal endoscopy is performed. The endoscopy reveals a peptic ulcer. He is prescribed omeprazole, a gastric proton pump inhibitor. What type of cell membrane transport is inhibited by this medication? A. Facilitated diffusion B. Osmosis C. Primary active transport D. Secondary active transport E. Simple diffusion 15. In which of the following membrane trans- port processes is the substance moving by facilitated diffusion? A. Calcium from sarcoplasm into sarcoplasmic reticulum B. Glucose from plasma into red blood cells C. Glucose from gut lumen into intestinal epithelial cells D. Potassium from extracellular space into striated muscle fibers E. Sodium from neuronal cytoplasm into extracellular space 16. A circulating hormone binds to an extracellu- lar receptor on a smooth muscle cell and initiates an intracellular response. This hormone most likely has which of the following properties? A. It is amphipathic. B. It is fat soluble. C. It is hydrophilic. D. It is lipophilic. E. It is nonpolar. 17. A circulating hormone binds to an extracel- lular receptor on epithelial tissue and initiates an intracellular response via activation of a second mes- senger. Which of the following can be classified as a second messenger? A. Adenylyl cyclase B. Cyclic AMP C. Epinephrine D. G-proteins E. Guanosine triphosphate 12. Which type of transport (passive diffusion, 1o active transport, 2o^ active transport) is utilized for the three described processes?

Nitric oxide across a smooth muscle cell membrane

Na+^ and glucose into intestinal cells

Na+^ out and K +^ into cardiac myocytes

A. Passive diffusion

1 o^ active transport

2 o^ active transport B. Passive diffusion

2 o^ active transport

1 o^ active transport C. Passive diffusion

1 o^ active transport

1 o^ active transport D. Passive diffusion

2 o^ active transport

2 o^ active transport E. 2 o^ active transport

1 o^ active transport

Passive diffusion F. 2 o^ active transport

Passive diffusion

1 o^ active transport G. 2 o^ active transport

1 o^ active transport

2 o^ active transport H. 2 o^ active transport

Passive diffusion

2 o^ active transport

13. During a routine newborn screening test, an infant tests positive for cystic fibrosis. This is an inherited condition in which the CFTR protein, a membrane chloride channel, is absent or nonfunc- tional. What effect will this have on water movement in cells with dysfunctional CFTR channels, compared to normal? A. An increased volume of water will move into cells. B. An increased volume of water will move out of cells. C. A reduced volume of water will move into cells. D. A reduced volume of water will move out of cells. E. Water movement will not be affected in these cells.

1.1 Questions

5

20. In a research study on obesity, it is shown that in the presence of insulin, the transport of d-glucose across the plasma membrane of adipose cells is much faster than the transport of l-glucose. Which of the following best explains the observed finding? A. Carrier-mediated transport of glucose B. Exchange transport of glucose C. Primary active transport of glucose D. Receptor-mediated endocytosis of glucose E. Simple diffusion of glucose 21. In the aftermath of an earthquake, humanitar- ian emergency volunteers handed out isotonic drink solutions containing NaCl and glucose to people with signs of dehydration. These oral rehydration solu- tions with NaCl and glucose are physiologically more effective than isotonic solutions containing NaCl only. Which of the following is the best explanation? A. A primary active glucose transporter at the basolateral intestinal cell membrane facilitates Na+^ and water reabsorption from the gut. B. Oral glucose increases insulin secretion, which then facilitates water reabsorption. C. The addition of glucose makes it more likely for the person to drink. D. The cotransport of glucose and Na+^ across the apical membrane of intestinal epithelial cells facilitates Na +^ and water absorption from the gut. E. The NaCl and glucose solution creates a higher osmotic pressure, which facilitates the uptake of water across the apical membrane of intestinal epithelial cells. 18. The body utilizes negative feedback systems to maintain homeostasis. The flow diagram provided shows the standard components of all negative feed- back systems. Which component of the negative feedback system is missing at the point labeled X on the diagram?

A. Afferent neurons

B. Brain

C. Effectors

D. Efferent neurons

E. Receptors

19. Five drugs are listed in the following table (A–E). If these drug molecules are all equally lipo- philic, which of the following conditions would produce the highest rate of transport of the drug molecule into a cell by simple diffusion?

Molecular weight

Intracel- lular con- centration (mM)

Extracel- lular con- centration (mM) Drug A 200 0.05 0. Drug B 250 1.0 0. Drug C 200 0.3 0. Drug D 200 0.5 0. Drug E 250 0.3 0.

A. Drug A

B. Drug B

C. Drug C

D. Drug D

E. Drug E

1.2 Answers and Explanations

7

is secondary active transport, since sodium is mov- ing down its concentration gradient while simulta- neously cotransporting glucose up its concentration gradient. Sodium and potassium are antiported across membranes using the Na+/K +^ ATPase, which utilizes ATP to move both cations against their con- centration gradients.

13. Correct: A reduced volume of water will move out of cells (D) Normally, the CFTR moves negatively charged chlo- ride ions out of the epithelial cells. Positively charged sodium ions follow passively, increasing the total electrolyte concentration in the extracellular space, which results in the movement of water out of the cell via osmosis. Hence, if the CFTR channels are dys- functional, less water will move out of cells. ( A , B ) Decreased electrolyte flow will limit (not increase) osmotic water movement. ( C ) In epithelial cells, the CFTR channel is part of a mechanism to move water out of (not into) cells. ( E ) Water movement will be affected, evident in that cystic fibrosis patients suf- fer from symptoms due to extracellular fluids with a low water content, such as sweat, digestive juices, and mucus. 14. Correct: Primary active transport (C) Proton pump inhibitors reduce stomach acid by blocking acid production. They work by inhibiting the gastric H+/K +-ATPase (proton pump), which is a primary active transport mechanism because it requires ATP to move the ions against their electro- chemical gradients. ( A ) Facilitated diffusion is a type of passive diffusion that does not require ATP, but involves a membrane protein for substances to pass through down their electrochemical gradient. ( B , E ) Osmosis and simple diffusion are passive transport mechanisms that do not require ATP. ( D ) Secondary active transport utilizes energy stored in an electro- chemical gradient to cotransport substances. One substance is transported with its gradient, while the other is transported against its gradient. 15. Correct: Glucose from plasma into red blood cells (B) Movement of glucose occurs via the GLUT1 trans- porter into red blood cells. Because glucose will be metabolized inside the cells, there is always a gradi- ent that drives glucose into the cells. ( A ) Calcium is transported by a calcium pump into the sarcoplas- mic reticulum via primary active transport. ( C ) Glu- cose is transported into intestinal epithelial cells by secondary active transport via the SGLT transporter. This is necessary so that glucose is always trans- ported toward the blood, despite varying gut glucose concentrations. ( D , E ) Sodium and potassium are either moving by simple diffusion through chan- nels, or transported by the Na-K ATPase, i.e., primary active transport. 9. Correct: PA ( C 1 – C 2 ) (B)

This is Fick’s first law of diffusion, describing the fac- tors influencing the net diffusion rate, J. J is propor- tional to the membrane permeability ( P ), the surface area for diffusion (A), and the concentration differ- ence across the membrane ( C 1 – C 2 ). The permeabil- ity, P , already includes the partition coefficient K , the diffusion coefficient D , and the membrane thickness ∆ x , as shown in answer C. ( A ) This is the bulk flow law. Flow is proportional to a difference in pressure (∆ P ) and inversely proportional to resistance ( R ). ( C ) This is the equation for the permeability, P. P = parti- tion coefficient ( K ) × diffusion coefficient (D) / mem- brane thickness (∆ x ). ( D ) This is the Stokes–Einstein equation, which expresses the relationship for the diffusion coefficient, D. D = [Boltzmann constant (B) × absolute temperature ( T )] / [6π × molecular radius ( r ) × viscosity of medium (η)]. ( E ) This is the Starling equation for transcapillary fluid movement. It is pro- portional to the difference of the hydrostatic pres- sure ( Pc capillary and P (^) i interstitial) and the oncotic pressure (π c capillary and π i interstitial).

10. Correct: From 1 to 2, 7 × 10 –5^ (A)

Substance A will diffuse from high to low concentra- tion down its concentration gradient, so it will dif- fuse from chamber 1 to chamber 2. Use the Fick law of diffusion to calculate the net rate of diffusion. J = PA ( C 1 – C 2 ) J = 7 × 10–5^ cm/sec × 2 cm^2 × (1.0 mmol/L – 0. mmol/L) J = 7 × 10 –5^ mmol/sec

11. Correct: Increase membrane surface area (D)

Based on the Fick law of diffusion [ J = PA ( C 1 – C 2 )], one of three changes will increase net diffusion across the lipid membrane. (1) An increase in the permeability of the substance, P ; (2) an increase in the surface area of the membrane, A ; or (3) an increase in the con- centration gradient across the membrane, C 1 – C 2. Therefore, an increase in membrane surface area is the best answer. ( A ) A decrease in chamber 1 con- centration will decrease the concentration gradient across the membrane, which will decrease diffusion rate. ( B ) A decrease in the permeability of substance A will decrease it net diffusion rate. ( C ) An increase in chamber 2 concentration will decrease the con- centration gradient across the membrane, which will decrease diffusion rate. ( E ) Increasing the water con- tent in chambers 1 and 2 by equal amounts will not change net diffusion rate.

12. Correct: Passive diffusion, 2 o^ active transport, 1o^ active transport (B)

Nitric oxide is a gas formed by endothelial cells. It diffuses passively across lipid membranes due to its lipid solubility. Sodium and glucose are cotrans- ported across membranes in the same direction using SGLT1 in the gastrointestinal tract. This cotransport

1 Cellular Physiology

8

19. Correct: Drug C (C) Based on the Fick law, the concentration gradient and molecular weight of a substance both play a role in diffusion across a membrane. The concentration gra- dient is greatest in drugs C and E, but since the size of the particle is considered in the permeability coef- ficient, the smaller particles pass through the mem- brane easier than large particles, so drug C is the best answer. ( A ) Drug A has the same molecular weight as drug C, but it has a smaller concentration gradient across the membrane (recall that the concentration gradient is the difference in concentration, not the ratio of concentrations), which reduces the diffusion rate. ( B ) Drug B has a negative concentration gradi- ent, so it will diffuse out of the cell, not into it. ( D ) Drug D has the same molecular weight has drug C, but it has a zero concentration gradient, so it will not diffuse across the membrane either way. ( E ) Drug E has the same concentration gradient as drug C, but a larger molecular weight, which reduces its diffu- sion rate. 20. Correct: Carrier-mediated transport of glucose (A) Glucose transport across adipose cell membranes is mediated by the carrier protein GLUT4 (the insulin- dependent glucose transporter). Carriers have speci- ficity, and the glucose carrier is stereo-selective for d-glucose. ( B ) Exchange transport of glucose occurs in the kidneys, but not in adipose tissue. ( C ) Primary active transport of glucose occurs in the gut, but not in adipose tissue. ( D ) Glucose is not transported via receptor-mediated endocytosis. ( E ) Glucose mol- ecules are too large to pass through the cell mem- brane via simple diffusion. (Note: a small amount of glucose can diffuse across the membrane via simple diffusion if given adequate time, but it is minimal.) 21. Correct: The cotransport of glucose and Na + across the apical membrane of intestinal epithelial cells facilitates Na +^ and water absorption from the gut. (D) The presence of glucose in the solution greatly increases the absorption of Na+^ and water because Na is cotransported with glucose into the intestinal epithelial cells by SGLT proteins. ( A ) Glucose is not transported with the help of an ATPase to provide a drag for water. ( B ) Insulin is not related to water reabsorption. ( C ) A better taste of the solution is not the reason for adding glucose. ( E ) Both solutions (with and without glucose) are isotonic. In addition, a hypertonic solution would facilitate diarrhea, not water reabsorption. 16. Correct: It is hydrophilic. (C) Circulating hormones are typically water soluble. They bind to extracellular receptors on cellular membranes because they are hydrophilic (water loving) and lipophobic (lipid fearing); thus they cannot pass directly through the lipid membrane. ( A ) Amphipathic substances have both hydrophilic and lipophilic properties. Common amphipathic substances are soaps, detergents, and lipoproteins. ( B , D ) Fat-soluble substances are lipophilic and can pass freely thorough a lipid membrane and directly activate intracellular mechanisms without a mem- brane transporter or intracellular second messenger system. ( E ) Molecules that have partially charged positive and negative areas are polar, and water-sol- uble substances are polar. 17. Correct: Cyclic AMP (B) Second messengers are intracellular signaling mol- ecules that are released by the cell in response to exposure to extracellular signaling molecules. They initiate an intracellular signaling cascade and trig- ger a physiological change. Some examples are cyclic AMP, calcium, inositol triphosphate (IP 3 ), and diacylglycerol. ( A ) Adenylyl cyclase is an enzyme that catalyzes the conversion of ATP to cyclic AMP and pyrophosphate. ( C ) Epinephrine is a hormone that is derived from the amino acid tyrosine and secreted by the medulla of the adrenal glands. ( D ) G-proteins are enzymes that are bound to G-pro- tein-coupled receptors and are involved in trans- mitting signals from a variety of stimuli from the outside to the inside of a cell. ( E ) Guanosine tri- phosphate (GTP) is essential to G-protein signaling in second-messenger systems, but it is not a second messenger itself. 18. Correct: Effectors (C) Negative feedback is a key regulatory mechanism for physiological function in living things. It is a regu- latory mechanism in which a change or stimulus is sensed by a sensor (receptor) and sends a message to the control center (usually the central nervous system). The control center then activates effectors, which will produce an effect to restore the initial change back toward normal. ( A ) Afferent neurons are involved in this pathway; they are indicated by the arrow between the sensors and the control cen- ter. ( B ) The brain or central nervous system is usually the control center. ( D ) Efferent neurons are involved in this pathway; they are indicated by the arrow between the control center and the X (effectors). ( E ) The receptors are the sensors.

1 Cellular Physiology

10

33. What are the patient’s estimated extracellular fluid volume and intracellular fluid volume in liters?

Extracellular fluid volume (in liters)

Intracellular fluid volume (in liters) A. 12 24 B. 12 36 C. 24 12 D. 24 36 E. 36 12 F. 36 14

34. What is the patient’s estimated blood volume in liters? A. 3. B. 4. C. 5. D. 6. E. 7. 35. Five volunteers of the same weight, height, and total body water are injected with 1 L of different solutions. The infusions are allowed to equilibrate, and no fluid is excreted. Which of the following solu- tions would cause the greatest increase in extracel- lular fluid volume? A. Hypertonic saline B. Isoosmotic urea C. Isotonic saline D. Plasma E. Water 36. Antidiuretic hormone (ADH) regulates water retention by acting to increase water reabsorption in the kidneys. If the ADH receptors are antagonized, what effects on intracellular fluid volume, extracel- lular fluid volume, and hematocrit are expected?

Intracellular fluid volume

Extracellular fluid volume

Hematocrit

A. ↑ ↑ ↑

B. ↑ ↑ ↓

C. ↑ ↓ ↓

D. ↓ ↓ ↓

E. ↓ ↓ ↑

F. ↓ ↑ ↑

Questions 30 to 31

The tank shown is divided in half by a membrane that is permeable to water and glucose but not fruc- tose. One liter of water is added to each side of the tank, with different concentrations of glucose and fructose, as illustrated in the image.

30. At time point zero, before any equilibration occurs, how does solution 1 compare to solution 2? A. It is hyperosmotic. B. It is hypoosmotic. C. It is isoosmotic. D. It is more saturated. E. It has more volume. 31. After one hour the system has reached equi- librium. At this time point, how does solution 1 com- pare to solution 2? A. It has a greater glucose molarity. B. It has a smaller glucose molarity. C. It has a greater volume of water. D. It has a smaller volume of water. E. It has a higher number of glucose particles.

Questions 32 to 34

A 42-year-old female patient has an annual exam. She weighs 60 kg. She complains of fatigue. Her hematocrit is 35%.

32. What is the patient’s estimated total body water in liters? A. 25 B. 28 C. 31 D. 34 E. 36

1.3 Questions

11

40. Subjects 1 and 2 are both 70-kg male sub- jects with the same total body water; depicted by the “normal state” in the image. Subject 1 drinks a hyperosmotic saline solution, while Subject 2 drinks a hypoosmotic saline solution. After steady-state equilibrium is achieved, which diagram best rep- resents the volume and osmolarity shift for each subject?

Subject 1 Subject 2 A. A B B. A C C. A D D. B A E. B C F. B D G. C A H. C B I. C D J. D A K. D B L. D C

37. Antidiuretic hormone (ADH) regulates water retention by acting to increase water reabsorption in the kidneys. If the ADH receptors are antagonized, what effect will this have on extracellular fluid osmo- larity and extracellular fluid Na+^ concentration?

Extracellular fluid osmolarity

Extracellular fluid Na +^ concentration A. ↑ ↑ B. ↑ ↓ C. ↑ ↔ D. ↓ ↑ E. ↓ ↓ F. ↓ ↔

38. Different tracer substances are used to mea- sure the volumes of different body compartments. Which tracers are used to measure total body water, extracellular fluid volume, and plasma volume, respectively?

Total body water

Extracellular fluid volume

Plasma volume A. Mannitol 3 H 2 O Evans blue dye B. Mannitol Evans blue dye

3 H 2 O

C.^3 H 2 O Mannitol Evans blue dye D.^3 H 2 O Evans blue dye

Mannitol

E. Evans blue dye

Mannitol 3 H 2 O

F. Evans blue dye

(^3) H 2 O Mannitol

39. 300 mL of a 2,500 mg/L mannitol solution is given to a patient intravenously. Two hours later a blood sample is taken, and the concentration of man- nitol in the plasma is 100 mg/L. Given the patient has a total body water volume of 25 L, what is the patient’s intracellular fluid volume in liters?

A. 7.

B. 15

C. 17.

D. 20

E. 25