Test Bank For Human Physiology From Cells to Systems 8TH Edition By Lauralee Sherwood | Complete Chapter 1-25 ()

In addition to providing for gas exchange, what are the other functions of the respiratory system? ANS: Answers will vary. PTS: 1 2. Describe the mechanics of ventilation. ANS: Answers will vary. PTS: 1 3. What factors influence the amount of gas exchange occurring at the respiratory membrane? ANS: Answers will vary. PTS: 1 4. Describe how haemoglobin’s saturation behaviour varies. ANS: Answers will vary. PTS: 1 5. How are respiratory events regulated? ANS: Answers will vary. PTS: 1 Chapter 12: The Urinary System MULTIPLE CHOICE 1. What is NOT a function of the kidneys? a. excretion of metabolic wastes b. maintaining proper plasma volume c. secreting aldosterone to regulate sodium d. maintaining proper osmolarity of body fluids ANS: C PTS: 1 REF: 507 BLM: Remember 360 2. What is NOT a function of the kidneys? a. contributing significantly to long-term regulation of arterial blood pressure by maintaining the proper plasma volume b. acting directly on the interstitial fluid, the fluid that bathes the cells, to maintain constancy in its composition c. excreting the metabolic waste products d. assisting in maintaining the proper acid-base balance of the body ANS: B PTS: 1 REF: 507 BLM: Remember 3. Which is the functional unit of the kidney? a. Glomerulus b. Nephron c. Medulla d. juxtaglomerular apparatus ANS: B PTS: 1 REF: 509 BLM: Remember 4. What is the specialized nephron capillary bed where filtration occurs? a. afferent arteriole b. efferent arteriole c. Glomerulus d. peritubular bed ANS: C PTS: 1 REF: 509 BLM: Remember 5. Which statement about juxtamedullary nephrons is INCORRECT? a. Their tubules lie in the renal cortex. b. They are important in the ability of the kidneys to concentrate urine. c. Their loops of Henle dip deep into the medulla. d. Their peritubular capillaries form vasa recta. ANS: A PTS: 1 REF: 511 BLM: Remember 361 6. What is NOT associated with juxtamedullary nephrons? a. glomeruli located in medulla b. long loops of Henle c. peritubular capillaries form vasa recta d. an important role in the ability of the kidneys to produce urine of varying concentration ANS: A PTS: 1 REF: 511 BLM: Remember 7. Below is a listing of nephron components and associated structures: 1. descending limb of loop of Henle 2. Bowman’s capsule 3. collecting tubule 4. ascending limb of loop of Henle 5. distal tubule 6. proximal tubule What is the correct flow of filtrate through these structures? a. 4, 6, 5, 3, 2, 1 b. 2, 6, 1, 4, 5, 3 c. 2, 5, 6, 3, 1, 4 d. 3, 2, 6, 1, 4, 5 ANS: B PTS: 1 REF: 511 BLM: Remember 8. What is/are NOT the function/s of peritubular capillaries? a. They drain into glomeruli. b. They take up the substances that are reabsorbed by the tubules. c. They supply substances that are secreted by the tubules. ANS: A PTS: 1 REF: 510 BLM: Remember 9. Which nephron structure is especially important in the kidney’s ability to produce urine of varying concentration? a. Bowman’s capsule b. proximal tubule c. distal tubule d. loop of Henle ANS: D PTS: 1 REF: 510 BLM: Remember 10. What are vasa recta associated with? a. afferent arterioles b. efferent arterioles c. cortical nephrons d. juxtamedullary nephron ANS: D PTS: 1 REF: 512 BLM: Remember 362 11. What is the renal process whereby substances are selectively transferred from the peritubular blood into the renal tubule? a. filtration b. secretion c. reabsorption d. excretion ANS: B PTS: 1 REF: 512 BLM: Remember 12. Which of the following is true about blood that flows through the kidneys? a. normally about 20 to 25 percent of the total cardiac output. b. all filtered through the glomeruli. c. all used to supply the renal tissue with O2 and nutrients. d. normally about 40 percent of the total cardiac output. ANS: A PTS: 1 REF: 520 BLM: Remember 13. Which statement is correct for glomerular filtration rate? The glomerular filtration rate _____. a. It averages 125 mL/min. b. It averages 75 litres/day. c. It represents 60 to 65 percent of the cardiac output. d. It averages 100 litres/day. ANS: A PTS: 1 REF: 516 BLM: Remember 14. Which statement is correct concerning glomerular filtrate? a. It is a plasma-free blood. b. It is formed as a result of passive forces acting across the glomerular membrane. c. It does not contain foreign compounds because these substances are secreted by special transport mechanisms in the proximal tubule instead. d. Its rate is increased by increased plasma protein level. ANS: B PTS: 1 REF: 513 BLM: Higher Order 15. What does filtrate NOT pass through? a. glomerular capillary pores b. basement membrane c. podocytes d. filtration slits ANS: C PTS: 1 REF: 514 BLM: Remember 16. The glomerular capillary blood pressure in the nephron is 78 mm Hg. The Bowman’s capsular hydrostatic pressure is 24 mm Hg. The colloidal osmotic pressure is 18 mm Hg. What is the net filtration pressure? a. 18 mm Hg b. 26 mm Hg c. 36 mm Hg d. 42 mm Hg 363 ANS: C PTS: 1 REF: 515 BLM: Higher Order 17. Which factor would reduce the net filtration pressure the most? a. vasodilation of the afferent arteriole b. vasocontraction of the efferent arteriole c. It has a large increase in blood colloid osmotic pressure d. It has a low capsular hydrostatic pressure ANS: C PTS: 1 REF: 515 BLM: Higher Order 18. Which statement concerning the process of glomerular filtration is correct? a. Bowman’s capsule hydrostatic pressure opposes filtration. b. The glomerular filtration rate is limited by a Tm. c. All of the plasma that enters the glomerulus is filtered. d. All of the plasma that enters the glomerulus is reabsorbed. ANS: A PTS: 1 REF: 515 BLM: Remember 19. Which statement is correct concerning glomerular filtration? a. It occurs in the loop of Henle. b. It is the process by which plasma water, electrolytes, and small molecules, which enter Bowman’s capsule, are separated from blood cells and protein, which remain in the glomerular capillaries. c. It is the process by which a substance is transported from the tubular fluid to the peritubular capillaries. d. It is greater when glomerular capsular pressure is higher. ANS: B PTS: 1 REF: 515 BLM: Remember 20. What would decrease the GFR? a. a fall in plasma protein concentration b. an obstruction such as a kidney stone in the tubular system, which increases Bowman’s capsule hydrostatic pressure c. vasodilation of the afferent arterioles d. a high hydrostatic pressure ANS: B PTS: 1 REF: 516 BLM: Remember 21. Which statement is NOT true for the macula densa? a. It consists of specialized tubular cells in the juxtaglomerular apparatus b. It consists of specialized arteriolar smooth-muscle cells in the juxtaglomerular apparatus c. It secretes renin ANS: B PTS: 1 REF: 517 BLM: Remember 364 22. What is NOT involved in autoregulation of the GFR? a. a myogenic mechanism in which the afferent arteriole automatically constricts when it is stretched b. a tubulo-glomerular feedback mechanism in which vasoactive chemicals released from the juxtaglomerular apparatus bring about afferent arteriolar vasoconstriction c. sympathetically induced vasoconstriction of the afferent arterioles ANS: C PTS: 1 REF: 517 BLM: Remember 23. Which of the following forces does NOT oppose/s glomerular filtration? a. blood colloid-osmotic pressure b. Bowman’s capsule hydrostatic pressure c. glomerular-capillary blood pressure ANS: C PTS: 1 REF: 516 BLM: Higher Order 24. Afferent arteriolar vasoconstriction _____ blood flow into the glomerulus, which causes the glomerular-capillary blood pressure to _____, leading to a(n) _____ in the net filtration pressure and a resultant _____ in the GFR. a. increases, increase, increase, increase b. decreases, decrease, decrease, decrease c. increases, increase, decrease, decrease d. decreases, decrease, increase, increase ANS: B PTS: 1 REF: 519 BLM: Higher Order 25. Which statement is NOT true for the myogenic mechanism? a. It causes the afferent arteriole to constrict when blood pressure is too high. b. It may result from stretching of vascular smooth muscle. c. It is under motor system control. ANS: C PTS: 1 REF: 517 BLM: Remember 26. What occurs after stimulation of the macula densa cells? a. vasodilation of the afferent arteriole b. vasoconstriction of the afferent arteriole c. increased GFR d. secretion of erythropoietin ANS: B PTS: 1 REF: 517 BLM: Remember 27. Which statement is NOT true for extrinsic control of the GFR? a. It is mediated by sympathetic nervous system input to the afferent arterioles. b. It is aimed at the regulation of arterial blood pressure. c. It is an autoregulatory mechanism ANS: C PTS: 1 REF: 518 BLM: Remember 365 28. When arterial blood pressure is elevated above normal, which compensatory change in renal function occurs as a result of the baroreceptor reflex? a. afferent arteriolar vasoconstriction b. afferent arteriolar vasodilation c. reduction in GFR d. efferent arteriolar vasoconstriction ANS: B PTS: 1 REF: 519 BLM: Higher Order 29. Which statement is NOT true concerning tubular reabsorption? a. It refers to the movement of a substance from the peritubular capillary blood into the tubular fluid. b. It occurs by either active or passive transport. c. It involves the process of transepithelial transport. ANS: A PTS: 1 REF: 520 BLM: Remember 30. Which statement regarding tubular reabsorption is INCORRECT? a. It refers to the movement of a substance from the tubular fluid to the peritubular capillary blood. b. It is important for the conservation of substances important to the body, such as Na+ , Cl- , glucose, and amino acids. c. It can occur by active or passive transport mechanisms. d. It takes place only in the proximal tubule. ANS: D PTS: 1 REF: 520 BLM: Higher Order 31. Which statement regarding tubular reabsorption is NOT true? a. It involves the movement of substances from the peritubular capillaries into the tubular fluid. b. It involves the movement of substances from the tubular fluid into the peritubular capillaries. c. It is considered to be active if any one of the five steps of transepithelial transport is active. ANS: A PTS: 1 REF: 520 BLM: Higher Order 32. What does tubular reabsorption NOT involve? a. active transport b. endocytosis c. facilitated diffusion ANS: B PTS: 1 REF: 522 BLM: Remember 33. Which statement is NOT a step in transepithelial transport? a. movement of the substance through the cytosol of the tubular cell b. movement of the substance across the glomerular capillary wall c. movement of the substance across the luminal membrane of the tubular cell d. movement of the substance through the interstitial fluid 366 ANS: B PTS: 1 REF: 522 BLM: Higher Order 34. What is the location of the Na+ –K + ATPase transport system that plays a pivotal role in much of tubular reabsorption? a. luminal membrane of tubular cells b. basolateral membrane of tubular cells c. podocytes d. glomerular capillary membrane ANS: B PTS: 1 REF: 522 BLM: Remember 35. What is NOT reabsorbed by the proximal convoluted tubule? a. sodium b. lipids c. glucose ANS: B PTS: 1 REF: 522 BLM: Remember 36. Into which structure does most reabsorption occur? a. proximal convoluted tubule b. glomerulus c. distal convoluted tubule d. loop of Henle ANS: A PTS: 1 REF: 522 BLM: Higher Order 37. Why is glucose NOT normally found in the urine? a. Glucose does not get filtered out of glomerulus. b. Glucose is not found in the blood. c. Glucose is usually reabsorbed by renal tubule cells. d. Glucose is kept in the blood. ANS: C PTS: 1 REF: 527 BLM: Higher Order 38. Which statement regarding the proximal tubule is NOT true? a. It reabsorbs about 65 percent of the filtered water. b. It is the site of action of renin. c. It is the location where glucose is reabsorbed. ANS: B PTS: 1 REF: 522 BLM: Remember 39. Which statement regarding tubular maximum (Tm) is NOT true? a. It is the maximum amount of a substance that the tubular cells can actively transport within a given time period. b. It is the maximum rate at which a substance is filtered at the glomerulus. c. It occurs when the membrane carrier becomes saturated. ANS: B PTS: 1 REF: 526 BLM: Remember 367 40. Which statement regarding tubular maximum (Tm) is correct? a. It is rate of glomerular filtration. b. It is the rate at which a substance can be reabsorbed because of saturation of the carrier molecule. c. It is the rate at which a substance can be cleared from the blood. d. It is the percentage of renal blood flow that can be converted to filtrate. ANS: B PTS: 1 REF: 526 BLM: Remember 41. Which statement regarding the renal threshold is correct? a. It is the maximum amount of a particular substance that can be excreted in the urine per unit of time. b. It is the maximum amount of a particular substance that the tubular cells are capable of actively reabsorbing per unit of time. c. It is the plasma concentration of a particular substance at which its Tm is reached and the substance first appears in the urine. d. It is the maximum amount of waste product that can be concentrated in the urine per unit of time. ANS: C PTS: 1 REF: 527 BLM: Remember 42. Which plasma constituent is NOT regulated by the kidneys? a. Glucose b. Na+ c. H + d. Phosphate ANS: A PTS: 1 REF: 527 BLM: Remember 43. Which statement is correct for reabsorption of chloride? a. It is active. b. It is passive. c. It is dependent on the amount of sodium reabsorbed. d. It is passive and dependent on the amount of sodium reabsorbed. ANS: D PTS: 1 REF: 528 BLM: Remember 44. What is the major waste product of nitrogen metabolism? a. plasma proteins b. Urea c. Glucose d. amino acids ANS: B PTS: 1 REF: 529 BLM: Remember 368 45. Given the following data for substance X (GFR = 125 mL/min, Tm = 125 mg/min, at a plasma concentration of 200 mg/100 mL), how much of substance X is filtered, reabsorbed, and excreted? a. 125 mg/min filtered, 125 mg/min reabsorbed, 0 mg/min excreted b. 200 mg/min filtered, 125 mg/min reabsorbed, 75 mg/min excreted c. 250 mg/min filtered, 125 mg/min reabsorbed, 125 mg/min excreted d. 250 mg/min filtered, 200 mg/min reabsorbed, 50 mg/min excreted ANS: C PTS: 1 REF: 527 BLM: Higher Order 46. Which statement regarding the juxtaglomerular apparatus is NOT true? a. It secretes renin in response to sodium depletion or plasma volume reduction. b. It is a thickened region of specialized cells at a point where the distal tubule comes into intimate contact with the afferent and efferent arterioles of the same nephron. c. It is where reabsorption of sodium occurs. ANS: C PTS: 1 REF: 523 BLM: Higher Order 47. What is the normal glucose concentration in the plasma in terms of mg per 100 mL? a. 30 b. 60 c. 100 d. 180 ANS: C PTS: 1 REF: 527 BLM: Remember 48. Which statement regarding sodium reabsorption is INCORRECT? a. It plays a role in glucose, amino acid, and urea reabsorption in the proximal tubule. b. It is under hormonal control in the distal tubule. c. In the loop of Henle, it contributes to the formation of concentrated urine. d. Approximately 0.5 percent of sodium is reabsorbed on a daily basis. ANS: D PTS: 1 REF: 522 BLM: Remember 49. Which statement regarding the juxtaglomerular apparatus is NOT true? a. It is a combination of specialized tubular and vascular cells at a point where the beginning of the distal tubule comes into intimate contact with the afferent and efferent arterioles of the same nephron. b. It secretes aldosterone. c. It secretes renin. ANS: B PTS: 1 REF: 523 BLM: Higher Order 50. Which statement regarding aldosterone is NOT true? a. It stimulates Na+ reabsorption in the distal and collecting tubules. b. It is secreted by the JG apparatus. c. It stimulates K+ secretion in the distal tubule. ANS: B PTS: 1 REF: 523 BLM: Remember 369 51. Which statement regarding aldosterone secretion is INCORRECT? a. It occurs in the kidney. b. It is stimulated by angiotensin II. c. It is controlled by the concentration of Cl– . ANS: B PTS: 1 REF: 523 BLM: Remember 52. Which statement about Na+ reabsorption is INCORRECT? a. It uses 80 percent of the energy requirement of the kidney. b. It is under control of the hormone aldosterone in the distal portions of the nephron. c. It is not linked to the reabsorption of amino acids and urea. ANS: C PTS: 1 REF: 523 BLM: Remember 53. Where does the greatest percentage of Na+ reabsorption takes place? a. proximal tubule b. loop of Henle c. distal tubule d. collecting tubule ANS: A PTS: 1 REF: 523 BLM: Remember 54. What happens when blood volume becomes abnormally low? a. Sodium reabsorption is diminished. b. Dilute urine is formed. c. Renin catalyzes the conversion of angiotensinogen. d. Aldosterone is secreted by the kidney. ANS: C PTS: 1 REF: 523 BLM: Higher Order 55. Which statement regarding angiotensin I is NOT true? a. It is formed as a result of activation of angiotensinogen by renin. b. It is transformed into angiotensin II as a result of converting enzyme action in the lungs. c. It acts on the adrenal cortex to stimulate aldosterone secretion. ANS: C PTS: 1 REF: 523 BLM: Remember 56. What stimulates sodium reabsorption in the distal portions of the nephron? a. atrial natriuretic peptide b. vasopressin c. angiotensin II d. aldosterone ANS: D PTS: 1 REF: 523 BLM: Remember 370 57. Which statement is NOT attributable to atrial natriuretic peptide (ANP)? a. ANP is released from the cardiac atria when the ECF volume is reduced. b. ANP inhibits Na+ reabsorption in the distal parts of the nephron. c. ANP inhibits renin secretion by the kidneys. d. ANP inhibits aldosterone secretion by the adrenal cortex. ANS: A PTS: 1 REF: 525 BLM: Remember 58. What is the energy required for glucose reabsorption used for? a. to run the Na+ –K + ATPase pump b. to run the Na+ -glucose co-transport carrier c. to maintain the Tm for glucose d. to produce aldosterone-induced protein, which increases the permeability of the proximal tubular cells to glucose ANS: A PTS: 1 REF: 522 BLM: Higher Order 59. Which statement regarding atrial natriuretic peptide is NOT true? a. It is secreted by the heart when atrial pressure is high. b. It results in decreased glomerular filtration rate. c. It inhibits aldosterone activity. ANS: C PTS: 1 REF: 525 BLM: Remember 60. What does NOT play a role in Na+ reabsorption? a. renin b. vasopressin c. angiotensinogen d. aldosterone ANS: B PTS: 1 REF: 523 BLM: Remember 61. What are the distal and collecting tubules the site of? a. the co-transport carriers for glucose and amino acid reabsorption b. the organic ion secretory systems c. aldosterone and vasopressin action d. glucose reabsorption ANS: C PTS: 1 REF: 528 BLM: Remember 62. Where is water reabsorption under the control of vasopressin? a. along the entire length of the nephron b. only in the loop of Henle c. only in the distal and collecting tubules d. only in the proximal tubule ANS: C PTS: 1 REF: 537 BLM: Remember 371 63. Which statement regarding water reabsorption is NOT true? a. It occurs passively by osmosis in the proximal tubule. b. It is under the control of vasopressin in the distal and collecting tubules. c. It occurs by active transport in the distal and collecting tubules. ANS: C PTS: 1 REF: 528 BLM: Remember 64. Which statement concerning water reabsorption is correct? a. Water reabsorption is under control of vasopressin throughout the length of the nephron. b. The ascending limb of the loop of Henle is always impermeable to water. c. Vasopressin makes the distal and collecting tubules impermeable to water. d. Fifteen percent of the filtered water osmotically follows the absorption of Na + and other solutes in the proximal tubule. ANS: B PTS: 1 REF: 536 BLM: Remember 65. Which statement regarding water reabsorption is NOT true? a. It cannot occur from any portion of the nephron in the absence of vasopressin. b. It occurs to the greatest extent in the proximal convoluted tubule. c. It is under vasopressin control in the distal and collecting tubules. ANS: A PTS: 1 REF: 537 BLM: Remember 66. Which statement regarding urea is NOT true? a. It is the waste product with the smallest molecular size in the glomerular filtrate. b. It is in greater concentration at the end of the proximal tubule than in other body fluids. c. It has a clearance rate greater than GFR. ANS: C PTS: 1 REF: 533 BLM: Remember 67. Which statement is NOT true for urea? a. It is a waste product resulting from the breakdown of protein. b. It is passively reabsorbed at the end of the proximal tubule down a urea concentration gradient created by the osmotic-induced reabsorption of water from the proximal tubule. c. Recycling between the late portion of the collecting tubule and the long loops of Henle contributes to medullary hypotonicity. ANS: C PTS: 1 REF: 529 BLM: Remember 68. What happens to the tubular secretion when the extracellular fluid becomes too acidic? a. No ionic substance is affected. b. Hydrogen ions decrease. c. Hydrogen ions increase. d. Sodium ions decrease. ANS: C PTS: 1 REF: 530 BLM: Higher Order 372 69. Which statement regarding tubular secretion is correct? a. It refers to the movement of a substance from the peritubular capillary blood into the tubular lumen. b. It can occur by active or passive transport mechanisms. c. Tubular secretion of K+ occurs in proximal convoluted tubules and is stimulated by aldosterone. ANS: C PTS: 1 REF: 530 BLM: Remember 70. Which statement regarding tubular secretion is NOT true? a. It involves transepithelial transport. b. It is the movement of a substance from the peritubular capillary blood into the tubular fluid. c. It always occurs by active transport. d. a and b. ANS: C PTS: 1 REF: 530 BLM: Remember 71. Why is tubular secretion important? a. It is involved in the renal regulation of hydrogen ion concentration. b. It is for the elimination of metabolic waste products from the body. c. It is in the renal regulation of sodium balance. d. for glucose secretion. ANS: A PTS: 1 REF: 530 BLM: Remember 72. Where does tubular secretion of foreign substances such as drugs generally occur? a. Bowman’s capsule b. the loop of Henle c. the proximal tubule d. the collecting duct ANS: D PTS: 1 REF: 532 BLM: Remember 73. Which statement is NOT true for potassium? a. It is secreted in the proximal tubule. b. It is actively secreted in the distal and collecting tubules. c. Its secretion is controlled by aldosterone. ANS: A PTS: 1 REF: 530 BLM: Remember 74. Which substance is NOT normally secreted into the tubule? a. hydrogen ions b. potassium ions c. glucose ANS: C PTS: 1 REF: 542 BLM: Higher Order 373 75. Which of the following does NOT stimulate(s) aldosterone secretion? a. an increase in plasma K+ b. a decrease in plasma K+ c. activation of the renin-angiotensin pathway ANS: B PTS: 1 REF: 523 BLM: Higher Order 76. Which statement with regards to plasma clearance is correct? a. It is the time required to filter blood in the glomerulus. b. It is the amount of a substance appearing in the urine in one minute. c. It is the amount of a substance filtered in one minute. d. It is the volume of plasma that is completely cleared of a substance by the kidneys in one minute. ANS: D PTS: 1 REF: 533 BLM: Remember 77. Which statement with regards to inulin is correct? a. It is filtered, not reabsorbed, but secreted. b. It is filtered, not reabsorbed, and not secreted. c. It is filtered, reabsorbed, and not secreted. d. It is filtered, reabsorbed, and secreted. ANS: B PTS: 1 REF: 533 BLM: Remember 78. The plasma clearance of a substance can be used to calculate the glomerular filtration rate (GFR) if that substance is freely filtered at the glomerulus and which? a. secreted and reabsorbed by the tubules. b. neither reabsorbed nor secreted by the tubules. c. secreted by the tubules. d. reabsorbed by the tubules. ANS: B PTS: 1 REF: 533 BLM: Remember 79. Which statement concerning the medullary vertical osmotic gradient is INCORRECT? a. The loops of Henle of juxtamedullary nephrons establish a medullary vertical osmotic gradient by means of countercurrent multiplication. b. The vasa recta enable the medulla to be supplied with blood while conserving the medullary vertical osmotic gradient by means of countercurrent exchange. c. The countercurrent system establishes and maintains a medullary vertical osmotic gradient ranging from 300 to 1,200 mosm/litre. d. The collecting tubules of the juxtamedullary nephrons but not the cortical nephrons descend through the medullary vertical osmotic gradient before emptying into the renal pelvis. ANS: D PTS: 1 REF: 536 BLM: Higher Order 374 80. What establishes the medullary vertical osmotic gradient by means of countercurrent multiplication? a. loops of Henle of juxtamedullary nephrons b. loops of Henle of cortical nephrons c. vasa recta of juxtamedullary nephrons d. vasa recta of cortical nephrons ANS: A PTS: 1 REF: 536 BLM: Remember 81. Which statement is correct for the ascending limb of the loop of Henle of a juxtamedullary nephron? a. It actively transports NaCl out of the lumen into the interstitial fluid. b. It is highly impermeable to H2O. c. It is always impermeable to H2O. d. Both a and c. ANS: D PTS: 1 REF: 536 BLM: Remember 82. What does NOT contribute to the establishment of a vertical osmotic gradient in the interstitial fluid of the renal medulla? a. the renin-angiotensin-aldosterone system b. countercurrent multiplication in the long loops of Henle of juxtamedullary nephrons c. urea recycling between the late portion of the collecting tubule and the long loops of Henle d. active transportation of sodium out of ascending limb of the loop of Henle ANS: A PTS: 1 REF: 542 BLM: Remember 83. The tubular fluid is _____ as it enters Bowman’s capsule, _____ at the beginning of the loop of Henle, _____ at the tip of the loop, and _____ as it leaves the loop to enter the distal tubule. a. isotonic, hypertonic, hypertonic, isotonic b. isotonic, isotonic, hypotonic, hypotonic c. isotonic, isotonic, hypertonic, hypotonic d. hypertonic, hypotonic, hypertonic, isotonic ANS: C PTS: 1 REF: 543 BLM: Remember 84. Which mechanism is NOT responsible for producing concentrated urine? a. The juxtamedullary nephrons become active. b. The countercurrent mechanism pulls out much water. c. ANP causes facultative water reabsorption in distal tubule. ANS: C PTS: 1 REF: 536 BLM: Remember 375 85. Which of the following is NOT true about the vertical osmotic gradient in the kidney? a. is established and maintained by the countercurrent system. b. makes it possible to put out urine of variable concentration, depending on the needs of the body, by varying the degree of water permeability of the distal portions of the nephron. c. is found in the renal cortex.