HBY 531 ORGAN SYSTEMS
Mid-Term Examination
2000

Section 1: Answer the following using:

A = becomes more negative
B = remains unchanged 
C = becomes more positive


1. The maximum diastolic potential of the SA node __________ after stimulation of the vagus nerve. 

2. The overshoot of the Purkinje fiber action potential __________ when half the external Na+ is replaced by an impermeant substitute. 

3. The maximum diastolic potential of a Purkinje fiber __________ when the extracellular [K+] in a tissue bath is elevated from 1 to 4 mM. 

4. The overshoot of the sinus node action potential __________ after application of TTX. 


Section 2: Answer the following using:

A = increases
B = no change, or remains unchanged
C = decreases


5. The duration of the QRS complex __________ after the plasma [K+] is elevated from 4 to 6 mM. 

6. The spontaneous firing rate of a Purkinje fiber _________ when the bath [K+] is reduced from 8 to 2 mM.

7. The duration of the sinus node action potential ________ after stimulation of the vagus nerve. (C)

8. The length of the diastolic interval of the sinus node _________ when a patient spikes a fever from 37*C to 39*C. 

9. During diastole, ventricular pressure __________ after an increase in ventricular end diastolic volume (EDV). 

10. At a constant preload, the pressure developed in the left ventricle _________ after the aortic diastolic pressure increases from 60 to 80 mmHg. 

11. As a patient progresses from moderate to severe heart failure, the volume of blood within the circulation ___________. 

12. As a constant flow of a Newtonian fluid passes along a tube of decreasing cross-sectional area, the pressure exerted onto the inner wall of the tube _____________. 

13. Following an infusion of a therapeutic (i.e., physiological) dose of isoproteronol, total peripheral resistance ______________. 

14. Mean arterial blood pressure ____________ during exercise in the presence of a non-specific * antagonist. 

15. Blood flow through a skeletal muscle ____________ following infusion of a nitric oxide (NO) synthase inhibitor. 

16. Venous compliance _______________ with venoconstriction. 

17. After clamping both carotid arteries above the level of (i.e., distal to) the baroreceptors, the frequency of action potentials within the efferent vagus __________. 

18. Beyond (i.e., distal to) segmental bronchi, the total resistance to airflow with successive generations of the airways because there are increasing numbers of units arranged in parallel. 

19. At low lung volumes, expiratory flow (as measured on an expiratory flow-volume curve) ___________ with increasing expiratory effort. 

20. During an operation, the arterial PCO2 of an anesthetized patient is monitored. The patient is ventilated using a mechanical ventilator, and the initial value is normal (PCO2 = 40 mmHg). If the ventilation is now increased so that the patient is hyperventilated, PCO2 ___________. 

21. Total pulmonary vascular resistance __________with increasing lung volumes above FRC. 

22. During muscular exercise, there is an increase in CO2 and temperature, and a decrease in pH at the metabolically active tissues. These changes shift the HbO2 dissociation curve to the right which ___________ the unloading of O2 to the tissues. 

23. The Haldane effect demonstrates that decreased hemoglobin saturation with O2 shifts the CO2 dissociation curve to the left. As a result, the CO2 content of the blood ___________. 

24. The filtered load of bicarbonate ___________ after an infusion of NaOH. 

25. Glomerular filtration rate _________ after an increase in cardiac atrial filling above normal. 

26. Renal potassium secretion (independent of any actions of aldosterone) __________ in response to hyperkalemia. 

27. Potassium secretion in the distal tubule _________ following an increase in flow through the distal tubule during a water diuresis. 

28. Arteriolar blood flow __________ after flow through the ascending limb increases to a supra-normal rate. 

29. The rate of net proximal tubular sodium reabsorption ___________ after an increase in the filtration fraction. 


Section 3: For each of the following, choose the single best response. 

30. A patient presenting with atropine intoxication would benefit from which of the following? 
a. A cholinesterase inhibitor
b. Tubocurarine
c. Vesamicol
d. A Ca2+ channel blocker
e. Botulinus toxin

31. Which of the following will inhibit norepinephrine release from nerve terminals of post-ganglionic sympathetic motor neurons? 
a. Phosphorylation of tyrosine hydroxylase
b. A Ca2+ ionophore
c. An *2 agonist
d. Caffeine
e. None of the above


32. With regard to cardiac muscle: 
a. Administration of cardiac glycosides results in an increase of Ca2+ transport by the Na+-Ca2+ exchanger.
b. An increase in cAMP levels will further increase the activity of the Ca2+ pump in the sarcoplasmic reticulum
c. The influx of Ca2+ from the interstitial fluid is responsible for 90% of the increase in intracellular Ca2+ during an action potential.
d. Blocking the Na+-K+ pump will have no effect in the strength of contraction.
e. None of the above.

33. The above figure shows the left ventricular pressure during a cardiac cycle. Regarding the marked points in the figure: 
a. Between points A and B, the ventricular volume decreases by 80%.
b. Between points C and D, the ventricular filling is at its maximum velocity (rapid ventricular filling).
c. Point C corresponds with the peak of v wave of the venous pulse.
d. QRS complex starts closest to A.
e. All of the above are correct.

34. What will be the oxygen consumption of a patient with a cardiac output of 5.5 L/min; a pulmonary vein O2 content of 0.20 mL of O2/mL of blood; and a pulmonary artery O2 content of 0.14 mL of O2/mL of blood? 
a. 330 mL of O2/min
b. 250 mL of O2/min
c. 350 mL of O2/min
d. 92 mL of O2/min
e. 110 mL of O2/min

35. Regarding the neuronal and hormonal regulation of cardiac function: 
a. Barorreceptors in the carotid sinus send information to the dorsal nucleus of the vagus and to the cardio-regulatory center in the medulla via cranial nerve IX.
b. The predominant tone is given by parasympathetic stimulation via cranial nerve X.
c. The feed back loop system does not include hormonal outputs.
d. a, b, c are correct
e. a and b are correct

(sorry, figure will be here soon)

36. In the figure above: the final increase in heart rate (arrow) after 4 equal doses of atropine (blocks parasympathetic) followed by propranolol (blocks sympathetic) or vice versa, is due to: 
a. Atropine has direct nerve stimulation effects.
b. Vagal input is predominant over sympathetic input.
c. The sequence of the drug infusion
d. Propranolol enhances atropine binding. (cooperativity)
e. Sympathetic input comes from the cervical sympathetic trunk.

37. A 500 mL venous infusion of saline into a person will have which of the following effects? 
a. There will be a decrease in mean arterial pressure.
b. There will be a decrease in the preload on the heart.
c. There will be an increase in heart rate. 
d. There will be a decrease in ANF release.

38. An increase in arterial vascular resistance will: 
a. decrease residual volume.
b. increase sympathetic output to the SA node.
c. increase preload on the heart.
d. decrease cardiac output. 

39. Cardiac output will not increase immediately after: 
a. sympathetic stimulation.
b. an increase in peripheral resistance. 
c. an increase in central venous pressure.
d. An infusion of atropine.






40. Which of the following statements most accurately describes the differences between the right and left heart? 
a. The right ventricle is more elastic than the left ventricle.
b. A larger stroke volume is ejected from the right ventricle.
c. A larger stroke volume is ejected from the left ventricle.
d. The atrial filling pressure is smaller on the right side than the left. 
e. None of the above statements are correct.

41. Suppose we inject 2.5 grams of inulin and 5 mg of Evan’s blue into a person. Following equilibration, we take an arterial blood sample and find that the inulin concentration is 0.1 grams/L; the Evan’s blue concentration is 1.43 mg/L; and the hematocrit is 0.40 (i.e., 40%). During equilibration, this individual voided 500 mL of urine containing 2 mg/mL of inulin and no Evan’s blue. From these data, the total blood volume of this person is: 
a. between 3 and 3.99 L
b. between 4 and 4.99 L
c. between 5 and 5.99 L
d. between 6 and 6.99 L
e. greater than or equal to 7 L

42. In an otherwise healthy individual, age-related decreases in arterial compliance correspond with: 
a. decreased pulse pressure.
b. increased myocardial O2 consumption (i.e., increased cardiac work).
c. increased stretch of the aorta during systole.
d. loss of the dicrotic notch of the aortic pressure wave.
e. both a and b.

43. Suppose that during exercise, the arteries supplying a given active skeletal muscle vasodilate to the extent that their radii double. Under these conditions one would expect that, compared to rest, blood flow to this muscle will: 
a. be decreased by a factor of 2.
b. remain unchanged.
c. be increased by a factor of 4
d. be increased by a factor of 8
e. be increased by a factor of 16.

44. Vascular smooth muscle tone will increase in response to all of the following EXCEPT: 
a. an increase in chloride conductance
b. stimulation with a non-specific * agonist
c. an increase in intracellular cAMP
d. an increase in the calcium conductance
e. both a and c.



45. The phenomena of flow-induced vasodilation can be abolished by which of the following? 
a. Treatment with a *2 agonist
b. Treatment with a *2 antagonist
c. Treatment with nitroprusside, a drug that relaxes smooth muscle
d. Removal of the endothelium
e. Both a and c

46. Capillary permeability is expected to be highest in which of the following? 
a. Continuous capillaries in the brain
b. Continuous capillaries in the heart
c. Fenestrated capillaries
d. Discontinuous capillaries
e. All of the above have equal permeability

47. Accumulation of interstitial fluid in systemic capillary beds would be expected in all of the following circumstances EXCEPT: 
a. right ventricle failure.
b. severe hypovolemia due to excessive sweating.
c. severe liver disease.
d. blockage of lymphatic vessels.
e. both a and b.

48. Clamping both common carotid arteries below the level of the carotid sinus will result in: 
a. an increase in the action potential frequency along baroreceptors fibers contained within Hering’s nerve.
b. an increase in the efferent vagal discharge to the heart.
c. an increase in total peripheral resistance.
d. a decrease in heart rate.
e. both a, b, and d.

49. Severe volume depletion will result in: 
a. an increase in heart rate.
b. a decrease in stroke volume.
c. an increase in ANP release.
d. systemic edema.
e. both a and b.

50. The above trace shows a typical Valsalva maneuver. In this figure, the changes in pressure that occur during phase 2 are attributable to: 
a. a decrease in central venous pressure.
b. the Bainbridge reflex.
c. an increase in the efferent vagal input to the heart.
d. stimulation of peripheral chemoreceptors
e. both c and d.

51. When a person lying on a tilt table is shifted from a horizontal to an upright position, arterial blood pressure is maintained through a combination of increased heart rate and: 
a. an increase in stroke volume.
b. an increase in total peripheral resistance.
c. an increase in central venous pressure.
d. a decrease in total peripheral resistance.
e. both a and b.

52. Compensatory mechanisms involved with hypovolemic shock include: 
a. an increase in heart rate.
b. an increase in total peripheral resistance.
c. an increase in circulating levels of angiotensin II.
d. an increase in circulating levels of epinephrine.
e. all of the above.

53. Which of the following is not true of the conducting airways?
a. They are anatomically incapable of participating in gas exchange.
b. They correspond to the first 16 generations of the airways.
c. They include the respiratory bronchioles.
d. Their role is to transport air between the environment and the gas exchange regions of the lungs.

54. For air to flow into the alveoli, 
a. alveolar pressure must be equal to atmospheric pressure.
b. alveolar pressure must be equal to intrapleural pressure.
c. alveolar pressure must be greater than atmospheric pressure.
d. alveolar pressure must be less than atmospheric pressure.
e. intrapleural pressure must become positive.

55. At functional residual capacity (FRC) capacity, 
a. the inward directed elastic recoil of the lung is greater than that of the outward directed elastic recoil of the chest wall.
b. the inward directed elastic recoil of the lung balances the outward directed elastic recoil of the chest wall.
c. the elastic recoil of both the lung and chest wall are directed outward.
d. the elastic recoil of both the lung and chest wall are directed inward.

56. Lung compliance: 
a. represents the relationship between changes in the pressure distending the alveoli and the corresponding changes in lung volume.
b. increases in restrictive pulmonary disease (i.e., pulmonary fibrosis).
c. can only be measured when air is flowing into or out of the lungs.
d. is greater at total lung capacity (TLC) than at functional residual capacity (FRC).
e. both a and c.

57. Structural interdependence of the alveoli refers to: 
a. maintaining stability of the alveoli by decreasing surface tension forces.
b. stabilizing forces generated by expanded alveoli on neighboring alveolar units.
c. the effect of changes in vascular pressures on alveolar transmural pressure.
d. the tendency to maintain relatively even distribution of the ventilation throughout the lung.

58. During the early portion of a forced expiration, when the lung volume is still high, 
a. there is more dynamic compression than when lung volume is low.
b. there is less alveolar elastic recoil than when lung volume is low.
c. airways resistance is greater than when lung volume is low.
d. the effective pressure gradient for airflow is greater than when lung volume is low.

59. A 55-year old man says he "can’t catch his breath" when he jogs or does any physical work. He noticed the problem about two years ago, and it seems to be getting worse. He says he coughs a lot, but he does not spit anything up. He says he has never smoked, but he has worked in a chemical plant for many years. You note that he has a respiratory rate of 25 breaths per minute, with small tidal volumes. He does not appear to be cyanotic. The results of the patient’s pulmonary function tests reveal that his measured lung volumes and capacities are 67% of the predicted values and that his FEV1/FVC is 90%. The patient’s history, breathing pattern, and pulmonary function tests are consistent with: 
a. restrictive disease.
b. obstructive disease.
c. both a and b.
d. none of the above.




60. In a patient with chronic obstructive pulmonary disease (COPD), resistance to airflow increases and the FEV1 is reduced due to which of the following factors? 
a. Excessive secretions in the airway 
b. Destruction of lung parenchyma and loss in radial traction on the airways
c. Reduction in the number of small airways
d. Loss of elastic recoil in the lung
e. All of the above factors may contribute to increased resistance to airflow and reduced FEV1.

61. Which patient has the highest alveolar ventilation? 
a. Tidal volume = 500 mL; Frequency = 20 breaths/min; Dead space volume = 200 mL
b. Tidal volume = 750 mL; Frequency = 14 breaths/min; Dead space volume = 200 mL
c. Tidal volume = 1000 mL; Frequency = 8 breaths/min; Dead space volume = 200 mL
d. Alveolar ventilation is the same in all cases

62. A normal person, seated upright, begins to inspire from functional residual capacity (FRC). The first 100 mL of inspired gas is labeled with xenon 133. Most of this radioactive gas will probably be found: 
a. in the conducting airways (i.e., anatomical dead space).
b. uniformly distributed to all alveoli.
c. in the alveoli in the lower portion of the lung.
d. in the alveoli in the upper portions of the lung.

63. Which of the following is not true when comparing the pulmonary and systemic circulations? 
a. Pulmonary vascular resistance is equal to total peripheral resistance.
b. Pulmonary vessels have less vascular smooth muscle than systemic arterial vessels.
c. Pulmonary vessels have thinner walls than systemic arterial vessels.
d. Pulmonary vessels are more distensible and compressible than systemic arterial vessels.
e. Pulmonary vessels have greater internal diameters than corresponding branches of the systemic arterial tree.

64. Which of the following situations would be expected to lead to an increase in the amount of lung under zone 1 conditions? 
a. Ascent to 15,000 feet above sea level
b. Moderate exercise
c. Positive-pressure ventilation with positive end-expiratory pressure (PEEP)
d. Changing from the standing to the supine position






65. A patient with severe carbon monoxide (CO) poisoning was given an exchange transfusion of stored blood. Measurement of his hemoglobin-oxygen dissociation curve showed a marked reduction in the P50. The most likely causative factor was: 
a. arterial CO2 retention.
b. reduced arterial pH in the transfused blood.
c. increased blood temperature.
d. reduced concentration of 2,3-DPG in the transfused red blood cells.
e. both b and d.

66. The apex, compared with the base, of the upright lung: 
a. has smaller alveoli.
b. is better perfused.
c. has a low ventilation-perfusion ratio.
d. has a low PO2.
e. has a low PCO2.

67. A patient with congenital heart disease has a right-to-left shunt and an arterial PO2 of 60 mmHg during air breathing. When he is given 100% O2, his arterial PO2 is virtually unaffected and he remains hypoxemic because: 
a. The time spent by the blood in the pulmonary capillary is insufficient for complete transfer of O2.
b. The shunted blood only comes in contact with poorly ventilated or unventilated alveoli.
c. The shunted blood bypasses ventilated alveoli and is therefore never exposed to the higher alveolar PO2.
d. The amount of O2 physically dissolved in solution does not increase.

68. What mechanism of is responsible for most, if not all, of the arterial hypoxemia of chronic obstructive pulmonary disease (COPD)?
a. Hypoventilation
b. Diffusion impairment
c. Shunt
d. Ventilation-perfusion inequality

69. Which of the following conditions would be expected to stimulate the peripheral (arterial) chemoreceptors? 
a. Inhalation of carbon monoxide (CO)
b. Mild anemia
c. Metabolic alkalosis
d. Ascent to high altitude





70. A lightly anesthetized patient (still capable of spontaneous breathing) is artificially ventilated at his normal tidal volume and twice his normal breathing frequency with a gas mixture of 50% O2 and 50% N2 for 10 minutes. On cessation of this artificial ventilation, the patient fails to breathe for 1 minute. The most likely cause of this temporary apnea is a:
a. change in activity of medullary chemoreceptors in response to changes in PCO2.
b. change in activity of peripheral(arterial) chemoreceptors in response to changes in PO2.
c. change in activity of pulmonary slowly adapting receptors (i.e., Hering-Breuer receptors).
d. change in activity of pulmonary rapidly adapting receptors (i.e., irritant receptors).

71. A 68-year old man complains of difficulty breathing and his ventilation is obviously very low. He says he has had the problem for a long time. In fact, he can’t remember when it started, and it seems to be getting worse. He coughs frequently and sometimes produces sputum upon arising. He says that he has smoked at least one pack of cigarettes a day since he was 20 years old. He appears to be cyanotic. His arterial blood gases reveal that he is hypoxemic (PO2 = 50 mmHg) but normocapnic (PCO2 = 43 mmHg). In an effort to help him, you administer O2 whereupon he stops breathing altogether. The most likely cause of this apnea is a: 
a. change in activity of medullary chemoreceptors in response to changes in PCO2.
b. change in activity of peripheral (arterial) chemoreceptors in response to changes in PO2.
c. change in activity of pulmonary slowly adapting receptors (i.e., Hering-Breuer receptors).
d. change in activity of pulmonary rapidly adapting receptors (i.e., irritant receptors).

72. Which of the following factors are most likely to lead to apneic episodes in patients with obstructive sleep apnea syndrome?
a. Snoring
b. Chronic sleep deprivation
c. Increased hypoxic drive during sleep
d. Increased vagal drive during sleep
e. Loss of tone of the genioglossus muscle

73. Which of the following is not a characteristic of the renal circulation? 
a. The afferent and efferent arterioles are both high resistance vessels, while the resistance of the glomerulus is low. 
b. The glomerular and peritubular capillaries are an example of a portal circulation. 
c. The innervation of the intrarenal arterial system includes a substantial number of parasympathetic nerves that regulate renal vascular tone.
d. The efferent arteriole of juxtamedullary nephrons divides into descending vasa recta which provide blood flow to the medullary tissues.




74. Which of the following statements about the glomerulus is TRUE?
a. The oncotic pressure of the plasma rises as the blood passes through the capillaries because of the filtration of protein-free fluid.
b. The podocytes are capable of contraction, which increases the hydraulic conductivity of the glomerular capillary wall. 
c. Net filtration pressure is just the difference between the hydrostatic pressure of the plasma and intratubular hydrostatic pressure.
d. The permselectivity characteristics of the endothelium are responsible for retarding the filtration of plasma proteins. 

75. Which of the following is FALSE? 
a. Constriction of the efferent arteriole will tend to increase the oncotic pressure of the plasma entering the peritubular capillaries, while decreasing intravascular hydrostatic pressure in the peritubular capillaries.
b. Mesangial cells within the glomerular capillary tuft are attached to the glomerular basement membrane and are important for maintaining the structural integrity of the glomerulus. 
c. Glomerulotubular balance describes the mechanism that links the rate of tubular reabsoprtion to the flow rate through the ascending limb. 
d. Normally, an acute rise in arterial blood pressure will not change GFR because of reflex adjustments in afferent arteriolar resistance mediated, in part, by tubuloglomerular feedback. 

76. Which of the following is FALSE? 
a. The majority of the sodium entry through the apical membrane of proximal tubular cells is the result of sodium-dependent secondary active transport of other solutes. 
b. Proximal tubular reabsorption of sodium requires permissive amounts of glucocorticoids. 
c. In the proximal tubule, the reabsorption of glucose is saturable, and the Tm is just above the normal plasma concentration of glucose. 
d. Substantial amounts of potassium are reabsorbed passively in the proximal tubule. 

77. Which of the following is FALSE? 
a. * intercalated cells secrete H+ while * intercalated cells secrete HCO3-. 
b. In the principal cells of the distal tubule, sodium enters the cells through aldosterone-dependent channels located on the apical membrane. 
c. In the principal cells of the collecting duct, the rate of water reabsorption will be inhibited by drugs that block the formation of cAMP. 
d. The fluid in the descending limb equilibrates with the medullary interstitium through active sodium secretion. 




78. A person is infused with PAH. After equilibration, PPAH is 0.05 mg/mL, UPAH is 25 mg/mL, and urine flow is 1.5 mL/min. What is renal plasma flow (RPF) in this person? 
a. 100 mL/min
a. 500 mL/min
b. 750 mL/min
c. None of the above are correct. 

79. A person is infused with inulin. After equilibration, urinary inulin excretion is 10 mg/min, and PI is 0.08 mg/mL. What is the GFR? 
a. 100 mL/min
b. 150 mL/min
c. 175 mL/min
d. None of the above are correct. 

80. A company measures the renal handling of a new antibiotic. The drug is freely filtered and not metabolized by in the body. Renal studies show that the excretion of the antibiotic exceeds the filtered load of the drug at all tested plasma concentrations. How is the antibiotic handled by the kidney tubules?
a. The antibiotic is not reabsorbed or secreted by the renal tubules.
b. The antibiotic is subjected to net secretion by the renal tubules.
c. The antibiotic is subjected to net reabsorption by the renal tubules.
d. There is not enough information to decide how the antibiotic is transported. 

81. Which of the following statements is FALSE?
a. The generation of urine that is hypotonic with respect to plasma requires both high ADH levels and adequate active Na+ reabsorption by the ascending limb.
b. Under normal conditions, the lumen of the thick ascending limb has a positive electrical potential with respect to the interstitium, and this drives passive, paracellular sodium reabsorption. 
c. The high urea concentrations in the inner medulla during an antidiuresis result from passive reabsorption of urea from the inner medullary collecting ducts, a process that is dependent on ADH.
d. Treatment with furosemide will increase the osmolarity of the fluid entering the distal tubule. 

82. Regarding the principal cells of the distal tubule, which of the following statements is FALSE? 
a. In response to ADH binding, preformed water channels are inserted into the apical membrane via a cAMP mediated signaling process. 
b. Increased dietary K+ intake will lead to increased uptake of K+ into the principal cells. 
c. Aldosterone binds to a cytosolic receptor and stimulates the synthesis of mitochondrial enzymes. 
d. With high ADH levels, the fluid leaving the distal tubule is hypertonic with respect to plasma. 

83. Which of the following statements is FALSE? 
a. Renin secretion will tend to rise in response to a rise in the luminal sodium chloride concentration at the macula densa. 
b. The juxtaglomerular cells that secrete renin are innervated by sympathetic nerves, and increased sympathetic activity increases renin secretion. 
c. Angiotensin II can stimulate both ADH secretion and thirst, and inhibit renin secretion.
d. After an increase in dietary salt intake, body weight will rise over the course of several days as the body content of both sodium and water increases. 

84. With respect to the renin-angiotensin-aldosterone system, which statement is TRUE? 
a. Renin secretion is stimulated by high blood pressure in the afferent arteriole.
b. Renin is secreted from macula densa cells located in the walls of the afferent arteriole. 
c. Angiotensin I is the product of renin-catalyzed proteolysis of angiotensinogen.
d. Angiotensin II directly stimulates ANP secretion. 

85. Which of the following statements about the distal tubule and collecting ducts is FALSE? 
a. The transport of sodium is strongly influenced by the sodium permeability of the luminal membrane. 
a. The rates of sodium and potassium reabsorption tend to change in parallel. 
b. K+ secretion into the lumen of the collecting ducts is passive and is influenced by the intracellular [K+].
c. The K+ secreted in these segments represents almost all of the K+ excreted in the urine. 

86. In which of the following conditions would you not expect a dissociation between effective circulating volume and extracellular volume? 
a. Ascites formation secondary to liver disease
b. Hypoalbuminemia secondary to glomerular injury
c. Congestive heart failure.
d. Hyperaldosteronism.

87. Regarding renal acid-base handling, which of the following statements is FALSE? 
a. In a respiratory acidosis, plasma PCO2 is elevated, and this leads to increased renal tubular H+ secretion. 
b. In a metabolic acidosis, the production of ammonia and the excretion of ammonium ion will both be increased. 
c. The reabsorption of bicarbonate in the proximal tubule involves active bicarbonate transport from the tubular lumen into the cytosol. 
d. Buffering by intracellular proteins and ions is slower than the buffering reactions in plasma. 



88. In response to an intravenous infusion of HCl, 
a. the [HCO3-] of plasma will be elevated by the buffering of the excess H+. 
b. renal ammonium ion excretion will fall. 
c. plasma PCO2 will rise, owing to a reduction in pulmonary ventilation. 
d. the pH of the blood leaving the kidney will be higher than systemic arterial pH.

89. A person’s arterial PCO2 is 25 mmHg and [HCO3-] is 10 mM. Calculate the person’s arterial pH and then indicate which of the following acid-base disorders is consistent with these values. 
a. Metabolic acidosis 
b. Metabolic alkalosis 
c. Respiratory acidosis 
d. Respiratory alkalosis

90. A person has a urine flow of 1500 mL/day. The urine contains 15 mmoles/liter titratable acid, 25 mmoles/liter ammonium, and 0 mmoles/liter HCO3-. What is the rate of urinary acid excretion? 
a. 60 moles/day 
b. 40,000 mmoles/day 
c. 40 mmoles/day 
d. 60 mmoles/day