Copyright © 2019, Elsevier Inc. All Rights Reserved. 1Chapter 03: The Cellular Environment: Fluids and Electrolytes, Acids and BasesMcCance/Huether: Pathophysiology: The Biologic Basis of Disease in Adults and Children, 8th EditionMULTIPLE CHOICE 1. Why are infants most susceptible to significant losses in total body water?a. High body surface-to-body size ratiob. Slow metabolic ratec. Kidneys are not mature enough to counter fluid lossesd. Inability to communicate adequately when he or she is thirstyANS: CRenal mechanisms that regulate fluid and electrolyte conservation are often not mature enough to counter the losses; consequently, dehydration may rapidly develop. Infants can be susceptible to changes in total body water because of their high metabolic rate and the turnover of body fluids caused by their greater body surface area in proportion to their total body size. An infant’s ability to communicate is limited and caregivers must become adept at reading their signals.PTS: 1 DIF: Cognitive Level: Remembering 2. Why does obesity create a greater risk for dehydration in people?a. Adipose cells contain little water because fat is water repelling.b. The metabolic rate of obese adults is slower than the rate of lean adults.c. The rate of urine output of obese adults is higher than in lean adults.d. The thirst receptors of the hypothalamus do not function effectively.ANS: AThe percentage of total body water (TBW) varies with the amount of body fat and age. Because fat is water repelling (hydrophobic), very little water is contained in adipose cells. Individuals with more body fat have proportionately less TBW and tend to be more susceptible to fluid imbalances that cause dehydration.PTS: 1 DIF: Cognitive Level: Remembering 3. A patient’s blood gases reveal the following findings: pH 7.3; bicarbonate (HCO3) 27 mEq/L; carbon dioxide (CO2) 58 mm Hg. What is the interpretation of these gases?a. Respiratory alkalosisb. Metabolic acidosisc. Respiratory acidosisd. Metabolic alkalosisANS: CThe values provided in this question characterize only acute uncompensated respiratory acidosis. Respiratory acidosis is characterized by a low pH and high CO2. Alkalosis is characterized by higher than normal pH. A metabolic acidosis would have a lower than normal pH with a bicarbonate concentration of <22 mEq/L.PTS: 1 DIF: Cognitive Level: Remembering 4. Water movement between the intracellular fluid (ICF) compartment and the extracellular fluid (ECF) compartment is primarily a function of what?a. Osmotic forcesb. Plasma oncotic pressurec. Antidiuretic hormoned. Hydrostatic forcesANS: AThe movement of water between the ICF and ECF compartments is primarily a function of osmotic forces.PTS: 1 DIF: Cognitive Level: Remembering 5. In addition to osmosis, what force is involved in the movement of water between the plasma and interstitial fluid spaces?a. Oncotic pressureb. Bufferingc. Net filtrationd. Hydrostatic pressureANS: DWater moves between the plasma and interstitial fluid through the forces of only osmosis and hydrostatic pressure, which occur across the capillary membrane. Buffers are substances that can absorb excessive acid or base to minimize pH fluctuations. Net filtration is a term used to identify fluid movement in relationship to the Starling hypothesis. Oncotic pressure encourages water to cross the barrier of capillaries to enter the circulatory system.PTS: 1 DIF: Cognitive Level: RememberingCopyright © 2019, Elsevier Inc. All Rights Reserved. 2 6. Venous obstruction is a cause of edema because of an increase in which pressure?a. Capillary hydrostaticb. Interstitial hydrostaticc. Capillary oncoticd. Interstitial oncoticANS: AVenous obstruction can increase the hydrostatic pressure of fluid in the capillaries enough to cause fluid to escape into the interstitial spaces. The remaining options are not causes of edema resulting from venous obstruction.PTS: 1 DIF: Cognitive Level: Remembering 7. At the arterial end of capillaries, why does fluid move from the intravascular space into the interstitial space?a. Interstitial hydrostatic pressure is higher than the capillary hydrostatic pressure.b. Capillary hydrostatic pressure is higher than the capillary oncotic pressure.c. Interstitial oncotic pressure is higher than the interstitial hydrostatic pressure.d. Capillary oncotic pressure is lower than the interstitial hydrostatic pressure.ANS: BAt the arterial end of capillaries, fluid moves from the intravascular space into the interstitial because capillary hydrostatic pressure is higher than the capillary oncotic pressure.PTS: 1 DIF: Cognitive Level: Remembering 8. Low plasma albumin causes edema as a result of a reduction in which pressure?a. Capillary hydrostaticb. Interstitial hydrostaticc. Plasma oncoticd. Interstitial oncoticANS: CAlbumin is the plasma protein that is primarily responsible for the plasma oncotic pressure because it has the highest concentration. Therefore a low concentration of albumin would lower the plasma oncotic pressure, leading to edema.PTS: 1 DIF: Cognitive Level: Remembering 9. How are secretion of antidiuretic hormone (ADH) and the perception of thirst stimulated?a. Decrease in serum sodiumb. Increase in plasma osmolalityc. Increase in glomerular filtration rated. Decrease in osmoreceptor stimulationANS: BSecretion of ADH and the perception of thirst are primary factors in the regulation of water balance. Thirst is a sensation that stimulates water-drinking behavior. Thirst is experienced when water loss equals 2% of an individual’s body weight or when osmotic pressure increases. A decrease in serum sodium would have the opposite effect. Increased glomerular filtration and decreased osmoreceptor stimulation would not lead to secretion of ADH and the feeling of thirst.PTS: 1 DIF: Cognitive Level: Remembering 10. Thirst activates osmoreceptors following an increase in which blood plasma component?a. Antidiuretic hormoneb. Aldosteronec. Hydrostatic pressured. Osmotic pressureANS: DThirst is experienced when water loss equals 2% of an individual’s body weight or when osmotic pressure increases. Dry mouth, hyperosmolality, and plasma volume depletion activate osmoreceptors (neurons located in the hypothalamus that are stimulated by increased osmotic pressure). Increased antidiuretic hormone, aldosterone, and hydrostatic pressure do not activate osmoreceptors.PTS: 1 DIF: Cognitive Level: Remembering 11. A student asks about
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