Chapter 12: Water and Electrolytes

Since the standard atomic weight of sodium is 22.99, the salt intake of an individual whose dietary sodium intake is 174 mmoles per day is: a. 10 g. b. 6000 mg. c. 3 g.

A. 10g

What percentage of blood volume is circulated through the kidneys? a. 25% b. 50% c. 75% d. 100%

A. 25%

In which part of the nephron is most of the filtered sodium reabsorbed? a. ascending loop of Henle b. distal convoluted tubule c. collecting ducts d. proximal tubule

A. Ascending loop of henle

Restoration of normal pH is accomplished by the ratio of bicarbonate to carbonic acid. Which buffer is controlled by the kidneys? a. bicarbonate b. carbonic acid

A. Bicarbonate

The most important problem resulting from dehydration during exercise is _____. a. hyperthermia b. hyponatremia c. loss of electrolytes d. excessive sweating

A. Hyperthermia

Which organs are responsible for regulation of extracellular water osmolarity and volume? a. hypothalamus and kidney b. liver and pancreas c. pancreas and kidney d. spleen and bone marrow

A. Hypothalamus and kidney

Colloid osmotic pressure attracts water into the plasma and is mainly due to _____. a. large protein molecules b. the pumping of the heart c. sodium ions d. chloride ions

A. Large protein molecule

Which of the following is NOT one of the principal regulatory mechanisms for guarding against fluctuation in pH? a. temperature variation b. buffer systems c. respiratory center d. renal regulation

A. Temperature variation

When hyperventilation occurs there is: a. an increased loss of CO2 and a decreased production of carbonic acid. b. a decreased loss of CO2 and an increased production of carbonic acid.

A. an increased loss of CO2 and a decreased production of carbonic acid.

For the specified conditions given in the table below, indicate if the components shown will increase (I) or decrease (D) immediately following the event and before homeostatic mechanisms return levels to normal. Drinking water after strenuous exercise Plasma Osmolality, Vasopressin, Aldosterone, Renin

A: plasma osmolality: decrease B: vasopressin: decrease C: Aldosterone: increase D: Renin: increase

Explain the relationship between dietary sodium intake and essential hypertension

Accumulation of sodium in body water is followed by retention of water and therefore expansion of blood volume, which increases intravascular pressure, resulting in hypertension. For those who do not excrete sodium normally, high dietary intake of sodium, which is almost completely absorbed, will result in essential hypertension.

Angiotensin II

Active hormone produced by angiotensin-converting enzyme in the lungs; functions as vasoconstrictor, as stimulator for release of aldosterone, and as stimulator of hypothalamus to release vasopressin.

Which hormone, stimulated by increased blood pressure stretching the heart, functions to inhibit sodium reabsorption to promote sodium excretion? a. vasopressin b. atrial natriuretic peptide c. aldosterone d. angiotensin II

B. ANP

When the plasma concentration of H ions exceeds the normal range the condition is called: a. alkalosis. b. acidosis

B. Acidosis

Which hormone, mediated by the enzyme renin, is primarily responsible for active reabsorption of sodium ions in the distal and collecting tubules? a. antidiuretic hormone b. aldosterone c. androsterone d. adrenocortical

B. Aldosterone

Which mineral is the most abundant anion found in extracellular fluid? a. sodium b. chloride c. phosphorus d. magnesium

B. Chloride

What is the condition that occurs in starvation or diabetes in which there is an increase in the urinary excretion of ammonia? a. metabolic alkalosis b. metabolic acidosis

B. Metabolic acidosis

When a person hyperventilates and "blows off" CO2, what effect does this have on pH? a. lowers it b. raises it c. does not alter it significantly d. delays any changes in it

B. Raises it

During a marathon it is important to provide _____ to prevent dehydration from excessive sweat loss. a. electrolyte-fortified drinks b. water c. fruit juices d. carbonated beverages

B. Water

Which body water reservoir is made up of plasma and interstitial fluid? a. intracellular b. extracellular c. total body water d. glomerular filtrate

B: extracellular

Incidence of hypertension in populations is considered predictable by _____. a. serum sodium concentration b. urinary sodium excretion c. average daily sodium intake d. sodium filtration rate by the kidney

C. Average daily sodium intake

Of these blood proteins, which one contributes most to buffering? a. albumin b. gamma globulins c. hemoglobin d. transthyretin

C. Hemoglobin

What is the major filtration force in the capillaries that is responsible for controlling movement of water from plasma to interstitial fluid and from interstitial fluid into plasma? a. colloid osmotic pressure b. theoretic osmotic pressure c. hydrostatic pressure d. effective osmotic pressure

C. Hydrostatic pressure

What is the condition that may result in cardiac arrhythmias when extracellular potassium is increased? a. hypernatremia b. hypokalemia c. hyperkalemia d. hyponatremia

C. Hyperkalemia

A food may be labeled "low sodium" if each serving provides a. less than 5 mg. b. less than 35 mg. c. less than140 mg. d. less than 240 mg.

C. Less than 140mg

Research has shown that supplements of which mineral are associated with significant reductions in both systolic and diastolic blood pressure, especially in individuals with hypertension? a. magnesium b. calcium c. potassium d. sodium

C. Potassium

Which is the chief cation of intracellular fluid for which maintenance of normal levels is essential to life of the cells? a. calcium b. sodium c. potassium d. bicarbonate

C. Potassium

Significant loss of what mineral occurs when one exercises vigorously while the temperature is high? a. sulphur b. phosphorus c. sodium d. potassium

C. Sodium

Acid-base balance refers to a. the ratio of acidic and basic foods consumed each day. b. the concentration of the bicarbonate ion in the red blood cells. c. the control of the hydrogen ion concentration in body fluids. d. homeostasis.

C. the control of the hydrogen ion concentration in body fluids.

Water accounts for what percentage of the body weight in a normal adult? a. 20% b. 40% c. 60% d. 80%

C: 60%

Which process gives the body the capacity to maintain constancy in the internal environment? a. osmotic pressure b. osmolality c. homeostasis d. acid-base balance

C: homeostasis

What percentage of the glomerular filtrate volume is excreted as urine each day? a. 100% b. 50% c. 25% d. 1%

D. 1%

A clinically useful parameter in establishing metabolic disorders that can alter electrolyte balance is: a. blood urea nitrogen. b. creatinine. c. homeostatic ion regulation. d. anion gap.

D. Anion gap

Which of the following is NOT a cationic electrolyte of extracellular fluid? a. sodium b. potassium c. calcium d. bicarbonate

D. Bicarbonate

Which of the components comprising the nephron includes the capillary network called the glomerulus? a. collecting duct b. distal convoluted tubule c. loop of Henle d. Bowman's capsule

D. Bowman's capsule

What enzyme facilitates diffusion of carbon dioxide from tissue cells and its reaction with water so that carbon dioxide can be carried to the lungs? a. renin b. angiotensinogen c. angiotensin d. carbonic anhydrase

D. Carbonic anhydrase

What is a major function of chloride? a. protein synthesis in cells b. the principal intracellular electrolyte c. wound healing d. maintenance of gastric acidity

D. Maintenance of gastric acidity

Which of the following foods is associated with reduced blood pressure? a. sugar b. alcohol c. red meat d. nuts

D. Nuts

Which mineral serves as the major intracellular fluid cation? a. calcium b. chloride c. sodium d. potassium

D. Potassium

Which of the physiological buffers has the most potent buffering capacity? a. bicarbonate-carbonic acid system b. hydrochloric acid system c. phosphates d. proteins

D. Proteins

Dietary intake of which mineral correlates positively with blood pressure? a. magnesium b. calcium c. potassium d. sodium

D. Sodium

Dehydration of just 2% can impair endurance performance. Briefly explain why

Dehydration reduces blood volume, which decreases maximal cardiac output per heartbeat. Therefore, to achieve the same oxygen delivery to exercising muscle, a higher heart rate is necessary but cannot fully compensate. A second impairment is the reduced sweat gland function as the body attempts to conserve body water. Reduced sweating can cause overheating and the need to end performance more quickly

For the specified conditions given in the table below, indicate if the components shown will increase (I) or decrease (D) immediately following the event and before homeostatic mechanisms return levels to normal. Loss of Blood Plasma osmolality, vasopressin, aldosterone, renin

E: plasma osmolality: decrease F: vasopressin: increase G: aldosterone: increase H: renin: increase

Renin

Enzyme produced by kidney; functions to hydrolyze angiotensinogen to angiotensin I.

Describe three mechanisms by which the kidneys conserve/excrete potassium or maintain potassium balance

Extracellular potassium, especially the blood level, is tightly regulated because it can be lethal if the concentration is too high or too low. Under ordinary circumstances 80% of potassium in the glomerular fitrate is reabsorbed. If blood potassium is too high, aldosterone is released to enhance the excretion of potassium and also causes more potassium to be secreted into the glomerular filtrate. Similarly, vasopressin can enhance excretion. If blood potassium is too low, less aldosterone is stimulated and more potassium is retained by the kidneys. A third mechanism that is less well understood can control potassium levels and acts especially after a high-potassium meal to prevent hyperkalemia. It involves the actions of insulin, glucagon, and a kidney protein that quickly removes potassium from the blood to prevent blood concentrations from becoming too high.

Discuss the role of calcium in control of blood pressure.

Higher calcium intake was first associated with lower blood pressure when communities with hard water were found to have lower death rates from cardiovascular disease. Subsequent trials of calcium supplementation have produced mixed data supporting the effect of supplementation in lowering high blood pressure. The mechanisms by which calcium may affect blood pressure are unclear.

Aldosterone

Hormone produced in adrenal cortex; functions to stimulate active reabsorption of sodium by the kidneys, thereby promoting fluid retention.

Atrial natriuretic peptide (ANP)

Hormone produced in atrial cells of the heart; functions to inhibit sodium reabsorption in the kidney, thereby promoting fluid loss.

Vasopressin

Hormone produced in hypothalamus; functions to conserve water by increasing reabsorption of water by the kidneys.

What is the normal range for the anion gap? What would an increase or decrease from the normal range indicate?

Normal range is 8 to 18 mEq/L. A greater gap occurs when metabolic acids such as lactate or ketones use up some of the bicarbonate measured to calculate the gap and cause a higher value for the anion gap. This would indicate acidosis. A lower gap happens when unmeasured anions decrease and the measured bicarbonate and chloride increase to keep electrical charge neutral. An example would be a circumstance in which albumin protein diminished severely

Two hormones that act at the distal renal tubular site to regulate plasma cation levels are: _____ and _____.

Parathyroid hormone, aldosterone

The anion gap is a clinically useful parameter for identifying metabolic disorders that affect electrolyte balance. How is it calculated?

The anion gap is calculated by using concentrations of blood sodium, chloride, and bicarbonate: Measured cations (Na+) - measured anions (Cl− + HCO3−) = anion gap.

What is the basis for replacing some of the NaCl in the diet with KCl, and how does it work?

The basis for replacing NaCl with KCl is that potassium has been associated with lower calcium urinary excretion, whereas sodium increases it. Studies where KCl replaces some NaCl, as well as studies with supplemental potassium citrate demonstrate reduced urinary calcium with the increased potassium.

Discuss the sequence of events of the maintenance of fluid homeostasis by the renin-angiotensin-aldosterone system.

The rennin-angiotensin-aldosterone system controls thirst and both sodium and water excretion to maintain fluid balance. When dehydration occurs and plasma volume falls or blood pressure falls in the glomerulus, active renin is secreted by the kidneys. Renin is an enzyme that converts angiotensinogen (made in the liver) in the bloodstream to angiotensin I. As angiotensin I passes through the lungs, antiotensin-converting enzyme changes it to angiotensin II. Angiotensin II has three important actions to restore blood volume. It acts on the hypothalamus to stimulate thirst and acts on the hypothalamus to stimulate production of vasopressin, which in turn acts on the kidney to retain water. Angiotensin II also acts on the adrenal cortex to stimulate production of aldosterone, which in turn acts on the kidney to increase reabsorption of sodium in the kidney tubules. Increased thirst and drinking behavior, plus increased retention of water and sodium by the kidney, serve to normalize fluid balance.