Unit V (25-32) - The body fluids and kidneys

Question 1

The major force favoring filtration across the glomerular capillary wall is the:

a. Oncotic pressure of the plasma.
b. Oncotic pressure of the glomerular filtrate.
c. Hydrostatic pressure of the blood.
d. Hydrostatic pressure of the glomerular filtrate.
e. Ultrafiltration coefficient

Answer 1

C. Hydrostatic pressure of the blood.

Cunningham Ch 41

Question 2

The glomerular filtration rate (GFR) is the:
a. Volume of blood filtered by the kidneys per minute per
kilogram of body weight.
b. Volume of plasma filtered by the kidneys per minute per kilogram of body weight.
c. Volume of urine produced by the kidneys per minute per kilogram of body weight.
d. Volume of glomerular filtrate formed by the kidneys per minute per kilogram of body weight.
e. Volume of blood cleared of creatinine by the kidneys per minute per kilogram of body weight.

Answer 2

d. Volume of glomerular filtrate formed by the kidneys per minute per kilogram of body weight.

Cunningham Ch 41

Question 3

In clinical practice the GFR is often estimated by determining the rate of creatinine clearance. The rate of creatinine clearance is the:

a. Volume of plasma cleared of creatinine/min/kg
b. Volume of glomerular filtrate formed/min/kg
c. Weight of creatinine filtered from the blood/min/kg
d. Weight of creatinine per volume of urine formed/min/kg
e. Difference between the rate of plasma flow in the afferent and efferent arterioles.

Answer 3

A. Volume of plasma cleared of creatinine/min/kg

Cunningham Ch 41

Question 4

The two major characteristics that determine whether a blood component is filtered or retained in the capillary lumen are its:

a. Molecular radius and molecular weight.
b. Molecular radius and lipid solubility.
c. Molecular radius and plasma concentration.
d. Molecular radius and electrical charge.
e. Molecular weight and length.

Answer 4

D. molecular radius and electrical charge

Cunningham Ch 41

Question 5

The GFR is increased by:

a. A low-protein meal.
b. Afferent arteriolar constriction.
c. Tubuloglomerular feedback.
d. Release of atrial natriuretic peptide.
e. Activation of RAAS

Answer 5

E. Activation of RAAS

Cunningham Ch 41

Question 6

Which segment of the renal tubule is responsible for the reabsorption of the bulk of filtered solutes?

a. Proximal tubule
b. Thin limbs of Henle’s loop
c. Thick ascending limb of Henle’s loop
d. Distal convoluted tubule
e. Collecting duct

Answer 6

A. Proximal tubule

Cunningham Ch 42

Question 7

The main driving force for the reabsorption of solutes from the tubule fluid is:
a. Active transport of solutes across the apical plasma
membrane.
b. Secondary active transport of solutes across the apical
plasma membrane.
c. Active transport of Na+ from the tubule epithelial cell
across the basolateral plasma membrane by the electrogenic Na+ channel.
d. Active transport of Na+ from the tubule epithelial cell
across the basolateral plasma membrane by the Na+,K+-
ATPase pump.
e. Passive diffusion of solutes through the paracellular
pathway.

Answer 7

D. Active transport of Na+ from the tubule epithelial cell
across the basolateral plasma membrane by the Na+,K+-
ATPase pump.

Cunningham Ch 42

Question 8

Glucose is found in the urine of an animal when:

a. Glucose transporters in the proximal tubule are inhibited by furosemide.
b. Glucose secretion in the proximal tubule is stimulated by angiotensin II.
c. Glomerular filtration barrier is defective causing increased glucose in the tubule fluid.
d. Plasma glucose is elevated, increasing glucose concentration in the tubule fluid above the proximal tubule transport capacity.
e. Elevated plasma glucose stimulates proximal tubule glucose secretion.

Answer 8

D. Plasma glucose is elevated, increasing glucose concentration in the tubule fluid above the proximal tubule transport capacity.

Cunningham Ch 42

Question 9

The ultimate rate of excretion of K+ in the urine is determined by the:
a. Concentration of K+ in the glomerular filtrate.
b. Proximal tubule, which reabsorbs or secretes K+ to meet the physiological requirements of the animals.
c. Thick ascending limb, where K+ secretion is enhanced by high plasma K+ concentrations.
d. Distal convoluted tubule, which has K+ pumps that are
inserted in the apical or basolateral plasma membranes,
depending on the need for reabsorption or secretion of K+.
e. Collecting duct, where the principal cells are capable of K+ secretion, and the intercalated cells are capable of K+ reabsorption.

Answer 9

E. Collecting duct, where the principal cells are capable of
K+ secretion, and the intercalated cells are capable of K+
reabsorption.

Cunningham Ch 42

Question 10

Which of the following two are effects of aldosterone on Na+ transport in the connecting segment and collecting duct?

a. Enhances the permeability of Na+ channels in the apical plasma membrane, thereby enhancing Na+ reabsorption
b. Stimulates Na+,K+-ATPase activity in the basolateral plasma membrane, thereby enhancing Na+ reabsorption
c. Reduces the Na+ permeability of the apical plasma membrane, thereby inhibiting Na+ reabsorption
d. Reduces Na+,K+-ATPase activity in the basolateral plasma membrane, thereby inhibiting Na+ reabsorption
e. Reduces the K+ permeability of the apical plasma membrane, thereby inhibiting K+ reabsorption

Answer 10

A. Enhances the permeability of Na+ channels in the apical
plasma membrane, thereby enhancing Na+ reabsorption

and

B. Stimulates Na+,K+-ATPase activity in the basolateral plasma membrane, thereby enhancing Na+ reabsorption

Cunningham Ch 42

Question 11

The bulk of filtered water is reabsorbed by which renal tubule segment?

a. Proximal tubule
b. Thin limbs of Henle’s loop
c. Thick ascending limb of Henle’s loop
d. Cortical collecting duct
e. Inner medullary collecting duct

Answer 11

A. Proximal tubule

Cunningham Ch 43

Question 12

The kidney responds rapidly to changing water requirements. The ability to alter quickly the rate of water excretion by greatly concentrating or diluting the urine is the result of several factors. Which of the following does not contribute to this ability?
a. Generation of hypertonic medullary interstitium
b. Countercurrent flow and differential salt and water permeabilities in the thin limbs of Henle’s loop
c. Dilution of the tubule fluid by the thick ascending limb and the distal convoluted tubule
d. Responsiveness of the collecting duct to antidiuretic
hormone (ADH)
e. ADH-regulated countercurrent flow and enhanced water permeability in the vasa recta

Answer 12

E. ADH-regulated countercurrent flow and enhanced water
permeability in the vasa recta

Cunningham Ch 43

Question 13

The hypertonic medullary interstitium is generated in large part by:
a. Active transport of Na+ by the straight portion of the proximal tubule.
b. Active reabsorption of Na+ by the water-impermeable,
ascending thin limb of Henle’s loop.
c. Active reabsorption of Na+ by the water-impermeable,
thick ascending limb of Henle’s loop.
d. Increase in water channels in the apical plasma membrane of collecting duct cells under the influence of
vasopressin.
e. Enhanced urea permeability of the thick ascending limb of Henle’s loop under the influence of vasopressin.

Answer 13

C. Active reabsorption of Na+ by the water-impermeable,
thick ascending limb of Henle’s loop.

Cunningham Ch 43

Question 14

In dehydration, ADH is released, which reduces water excretion by:
a. Enhancing water reabsorption in the proximal tubules by stimulating Na+,K+-ATPase.
b. Enhancing water reabsorption in the thick ascending limb by stimulating the insertion of aquaporin-2 water channels into the apical plasma membrane.
c. Enhancing water reabsorption in the collecting duct by
stimulating Na+,K+-ATPase activity.
d. Enhancing water permeability in the collecting duct by
stimulating the insertion of aquaporin-2 water channels
into the apical plasma membrane.
e. Reducing the glomerular filtration rate by activation of
tubuloglomerular feedback.

Answer 14

D. Enhancing water permeability in the collecting duct by
stimulating the insertion of aquaporin-2 water channels
into the apical plasma membrane.

Cunningham Ch 43

Question 15

In carnivores, the usual role of the kidney in maintaining acid base homeostasis is to:

a. Secrete excess bicarbonate.
b. Secrete excess ammonia.
c. Secrete excess acid.
d. Secrete excess carbon dioxide.
e. Secrete excess phosphate buffer.

Answer 15

C. Secrete excess acid

Cunningham Ch. 44

Question 16

The bulk of acid secretion (bicarbonate reabsorption) is
accomplished by which renal tubule segment?
a. Proximal tubule
b. Thin limbs of Henle’s loop
c. Thick ascending limb of Henle’s loop
d. Distal convoluted tubule
e. Collecting duct

Answer 16

A. Proximal tubule

Cunningham Ch. 44

Question 17

Which of the following factors does NOT contribute to efficient acid excretion (bicarbonate reabsorption) by the renal tubules?

a. Primary active transport of bicarbonate
b. Intraluminal buffering by bicarbonate
c. Intraluminal buffering by ammonia and phosphate
d. Intracellular and membrane-associated carbonic anhydrase
e. Transmembrane proton transport by the Na+/H+ exchanger, H+-ATPase pump, and H+,K+-ATPase pump

Answer 17

A. Primary active transport of bicarbonate

Cunningham Ch. 44

Question 18

Which of the following statements regarding mechanisms of acid-base regulation by the collecting duct is FALSE?
a. The cortical collecting duct responds to acidosis by increasing the net rate of acid secretion.
b. The cortical collecting duct responds to alkalosis with net bicarbonate secretion.
c. Proton and bicarbonate transport in the collecting duct are only slightly altered in response to systemic acid-base disturbances.
d. The collecting duct determines the ultimate pH of the
urine.
e. The intercalated cells are largely responsible for acid secretion by the collecting duct.

Answer 18

C.
Proton and bicarbonate transport in the collecting duct are only slightly altered in response to systemic acid-base
disturbances.

Cunningham Ch. 44

Question 19

What is the role of renal ammonia metabolism in the renal response to acidosis, at least in dogs and rodents?
a. Acidosis increases ammoniagenesis in the proximal tubule, which increases the generation of new bicarbonate ions.
b. Acidosis increases collecting duct ammonia secretion,
which enhances acid secretion.
c. Acidosis stimulates ammoniagenesis in the proximal tubule and inhibits collecting duct ammonia secretion, which increases ammonia buffering of the plasma.
d. Renal ammonia metabolism does not contribute to renal acid-base regulation.
e. Both a and b.

Answer 19

A. Acidosis increases ammoniagenesis in the proximal tubule, which increases the generation of new bicarbonate ions.

&

B. Acidosis increases collecting duct ammonia secretion,
which enhances acid secretion.

Cunningham Ch. 44

Question 20

What proportion of body weight is ECF vs ICF?

Answer 20

ECF - 1/3

ICF - 2/3

Question 21

What is the proportion of interstitial fluid vs plasma? and what is the main difference between the two?

Answer 21

Interstitial - 75% - more negative

Plasma - 25% - more negative (bc of the proteins), also has more cations

Question 22

What is normal osmolarity in dogs and cats?

Answer 22

Dogs - 280-300

Cats - 280 - 330

Question 23

Factors that lead to edema formation

Answer 23

1. Increased capillary filtration
   a. increase capillary permeability (filtration coefficient)
   b. increased capillary hydrostatic pressure
   c. decreased plasma oncotic pressure (low protein)
2. Lymphatic obstruction

Question 24

How is the hydrostatic pressure different in the glomerular capillaries compared to the peritublar capillaries? why?

Answer 24

glomerular - higher (60mmHg) - rapid filtration

peritubular - lower (13mmHg)- rapid reabsorption

Question 25

Which of the following nerves provides motor innervation to the detrusor muscle? 
A. Pelvic n.  
B. Pudendal n.
C. Femoral n. 
D. Hypogastric n.

Answer 25

A. Pelvic n.

Parasympathetic nerve - arises from S2-S3 and provides the principal nerve supply to the bladder. Also provides sensory to the bladder by detecting degree of stretch.

Question 26

Which of the following nerves provides sympathetic innervation to the bladder? 
A. Pelvic n.  
B. Pudendal n.
C. Femoral n. 
D. Hypogastric n.

Answer 26

D. Hypogastric n.

Responsible for bladder vasculature +/- pain sensation

Question 27

What is the lowest mean arterial pressure at which the kidney is able to maintain relatively constant GFR and renal blood flow?
A. 40mmHg
B. 60mmHg
C. 70 mmHg
D. 90 mmHg

Answer 27

B. 60mm Hg

Question 28

In normal kidneys, which of the following is true of the osmolarity of renal tubular fluid that flows through the early distal tubule in the region of the macula densa?

a. Usually isotonic compared with plasma
b. Usually hypotonic compared with plasma
c. Usually hypertonic compared with plasma
d. Hypertonic, compared with plasma, in antidiuresis

Answer 28

B Usually hypotonic compared with plasma

As water flows up the ascending limb of the loop of Henle, solutes are reabsorbed, but this segment is relatively imipermeable to water; progressive dilution of the tubular fluid occurs so that the osmolarity decreases to approximately 100 mOsm/L by the time the fluid reaches the early distal tubule. Even during maximal antidiruesis, this portion of the renal tubule is relatively impermeable to water and is therefore called the diluting segment of the renal tubule.

Guyton 13 ed. P 378-379

Question 29

When dietary intake of K+ increases, body K+ balance is maintained by an increase in K+ excretion primarily by which of the following?

a. Decreased glomerular filtration of K+
b. Decreased reabsorption of K+ by the proximal tubule
c. Decreased reabsorption of K+ by the thick ascending limb of the loop of Henle
d. Increased K+ secretion by the late distal and collecting tubules
e. Shift of K+ into the intracellular compartment

Answer 29

D Increased K+ secretion by the late distal and collecting tubules

Most of the daily variation in K+ excretion is caused by changes in K+ secretion in the late distal tubules and collecting tubules. Therefore, when the dietary intake of K+ increases, the total body balance of K+ is maintained primarily by an increase in K+ secretion in these tubular segments. Increased K+ intake has little effect on GFR or on reabsorption of K+ in the proximal tubule and loop of Henle. Although high K+ intake may cause a slight shift of K+ into the intracellular compartment, a balance between intake and output must be achieved by increasing the excretion of K+ during high K+ intake.

Guyton 13 ed.

Question 30

Which tends to increase GFR?

a. Increased afferent arteriolar resistance
b. Decreased efferent arteriolar resistance
c. Increased glomerular capillary filtration coefficient
d. Increased Bowman’s capsule hydrostatic pressure
e. Decreased glomerular capillary hydrostatic pressure

Answer 30

C Increased glomerular capillary filtration coefficient

This is the product of the hydraulic conductivity and surface area of the glomerular capillaries.

Guyton 13ed. P 337-340

Question 31

The GFR of a patient with glomerulonephritis decreases by 50% and remains at that level. For which substance would you expect to find the greatest increase in plasma concentration?

a. Creatinine
b. K+
c. Glucose
d. Na+
e. Phosphate
f. H+

Answer 31

A Creatinine

A 50% reduction of GRF would approximately double the plasma creatinine concentration because creatinine is not reabsorbed or secreted and its excretion depends largely on glomerular filtration. Therefore, when GFR decreases, the plasma concentration of creatinine increases until the renal excretion of creatinine returns to normal. Plasma concentrations of glucose, K+, Na+, and H+ ions are closely regulated by multiple mechanisms that keep them relatively constant even when GFR falls to very low levels. Plasma phosphate concentration is also maintained near normal until GFR falls to below 20-30% of normal.

Guyton 13 ed. P 435-436

Question 32

The maximum clearance rate possible for a substance that is totally cleared from the plasma is equal to which of the following?

a. GFR
b. Filtered load of that substance
c. Urinary excretion rate of that substance
d. Renal plasma flow
e. Filtration fraction

Answer 32

D Renal plasma flow

If a substance were completely cleared from the plasma, the clearance rate of that substance would equal the total renal plasma flow. In other words, the total amount of substance delivered to the kidneys in the blood (renal plasma flow x concentration of substance in the blood) would equal the amount of that substance excreted in the urine. Complete renal clearance of a substance would require both glomerular filtration and tubular secretion of that substance.

Guyton 13 ed. P 365-368

Question 33

Which changes would you expect to find after administering a vasodilator drug that caused a 50% decrease in afferent arteriolar resistance and no change in arterial pressure?

a. Decreased renal blood flow, decreased GFR, and decreased peritubular capillary hydrostatic pressure
b. Decreased renal blood flow, decreased GFR, and increased peritubular capillary hydrostatic pressure
c. Increased renal blood flow, increased GFR, and increased peritubular capillary hydrostatic pressure
d. Increased renal blood flow, increased GFR, and no change in peritubular capillary hydrostatic pressure
e. Increased renal blood flow, increased GFR, and decreased peritubular capillary hydrostatic pressure

Answer 33

C Increased renal blood flow, increased GFR, and increased peritubular capillary hydrostatic pressure

A 50% reduction in afferent arteriolar resistance with no change in arterial pressure would increase renal blood flow and glomerular hydrostatic pressure, thereby increasing GFR. At the same time, the reduction in afferent arteriolar resistance would raise peritubular capillary hydrostatic pressure.

Guyton 13 ed. P 338-340

Question 34

Which change tends to increase peritubular capillary fluid reabsorption?

a. Increased blood pressure
b. Decreased filtration fraction
c. Increased efferent arteriolar resistance
d. Decreased angiotensin II
e. Increased renal blood flow

Answer 34

C Increased efferent arteriolar resistance

The balance of hydrostatic and colloid osmotic forces in the peritubular capillaries determines peritubular capillary fluid reabsorption. Increased efferent arteriolar resistance reduces peritubular capillary hydrostatic pressure and therefore increases the net force favoring fluid reabsorption. Increased blood pressure tends to raise peritubular capillary hydrostatic pressure and reduce fluid reabsorption. Decreased filtration fraction increases the peritubular capillary colloid osmotic pressure and tends to reduce peritubular capillary reabsorption. Decreased angiotensin II causes vasodilation of efferent arterioles, raising peritubular capillary hydrostatic pressure, decreasing reabsorption, and decreasing tubular transport of water and electrolytes. Increased renal blood flow also tends to raise peritubular capillary hydrostatic pressure and decrease fluid reabsorption.

Guyton 13 ed. P 360-362

Question 35

An adrenal tumor that causes excess aldosterone secretion would tend to ____ plasma K+ concentration, ____ plasma pH, ____ renin secretion, and ____ blood pressure.

a. Decrease, decrease, decrease, decrease
b. Decrease, increase, decrease, increase
c. Decrease, decrease, decease, increase
d. Decrease, increase, increase, increase
e. Increase, increase, decrease, increase
f. Increase, decrease, decrease, increase

Answer 35

B Decrease, increase, decrease, increase

Excess aldosterone increases sodium reabsorption and potassium secretion by the principal cells of the collecting tubules, causing sodium retention, increased blood pressure, and decreased renin secretion while increasing excretion of potassium and tending to decrease plasma potassium concentration. Excess aldosterone also causes a shift of potassium from the extracellular fluid into the cells, further reducing plasma potassium concentration. Aldosterone excess also stimulates hydrogen ion secretion and bicarbonate reabsorption by the intercalated cells and tends to increase plasma pH (alkalosis). Therefore the classic manifestations of excess aldosterone secretion are hypokalemia, hypertension, alkalosis, and low renin levels.

Guyton 13 ed. P 356-357, 390

Question 36

Which of the following tends to increase potassium secretion by the cortical collecting tubule?

a. A diuretic that inhibits the action of aldosterone (e.g. spironolactone)
b. A diuretic that decreases loop of Henle sodium reabsorption (e.g. furosemide)
c. Decreased plasma potassium concentration
d. Acute metabolic acidosis
e. Low sodium intake

Answer 36

B A diuretic that decreases loop of Henle sodium reabsorption (e.g. furosemide)

Potassium secretion by the cortical collecting ducts is stimulated by 1) aldosterone, 2) increased plasma potassium concentration, 3) increased flow rate in the cortical collecting tubules, and 4) alkalosis. Therefore a diuretic that inhibits aldosterone, decreased plasma potassium concentration, acute acidosis, and low sodium intake would all decrease potassium secretion by the cortical collecting tubules. A diuretic that decreases loop of Henle sodium reabsorption, however, would tend to increase the flow rate in the cortical collecting tubule and therefore stimulate potassium secretion.

Guyton 13 ed. P 392, 396

Question 37

Which diuretic inhibits Na-2Cl-K co-transport in the loop of Henle as its primary action?
A. Thiazide diuretic
B. Furosemide
C. Carbonic anhydrase inhibitor
D. Osmotic diuretic
E. Amiloride
F. Spironolactone

Answer 37

B. Furosemide

Furosemide is a powerful inhibitor of the Na-2Cl-K co-transporter in the LOH. Thiazide diuretics primarily inhibit NaCl reabsorption into the distal tubule, whereas carbonic anhydrase inhibitors decrease bicarbonate reabsorption in the tubules. Amiloride inhibits sodium channel activity, whereas spironolactone inhibits the action of mineralocoricoids in the renal tubules. Osmotic diuretics inhibit water and solute reabsorption by increasing osmolarity of the tubular fluid.

Guyton 13 ed. p 428

Question 38

A selective decrease in efferent arteriolar resistance would \_\_\_\_ glomerular hydrostatic pressure, \_\_\_\_ GFR, and \_\_\_\_ renal blood flow.
A. Increase, increase, increase
B. Increase, decrease, increase
C. Increase, decrease, decrease
D. Decrease, increase, decrease
E. Decrease, decrease, increase
F. Decrease, increase, increase

Answer 38

E. Decrease, decrease, increase

Decreased efferent arteriolar resistance would increase renal blood flow while reducing glomerular hydrostatic pressure, which, in turn, would tend to decrease the GFR.

Guyton 13 ed. P 338-339

Question 39

Which nephron segment is the primary site of magnesium reabsorption under normal conditions?
A. Proximal tubule
B. Decsending limb of the loop of Henle
C. Ascending limb of the loop of Henle
D. Distal convoluted tubule
E. Collecting ducts

Answer 39

C. Ascending limb of the loop of Henle

About 65% of the filtered load of Mg is reabsorbed here. The proximal tubule normally reabsorbes only about 25% of filtered Mg., and the distal and collecting tubules reabsorb less than 5%

Guyton 13 ed. P 398

Question 40

The principal cells in the cortical collecting tubules
A. are the main site of action of the thiazide diurectics
B. have Na-Cl-K co-transporters
C. are highly permeable to urea during antidiuresis
D. are an important site of action of amiloride
E. are the main site of action of furosemide

Answer 40

D. are an important site of action of amiloride

Amiloride blocks entry of sodium into sodium channels. Thiazide diuretics inhibit Na-Cl co-transport in the early distal tubule. The collecting tubule cells are not very permeable to urea. Furosemide inhibits the Na-Cl-K co-transporter in the thick ascending LOH.

Question 41

The type A intercalated cells in the collecting tubules
A. are highly permeable to urea during antidiuresis
B. secrete K
C. secrete H
D. are the main site of action of furosemide
E. are the main site of action of thiazide diuretics

Answer 41

C. secrete H

Type A intercalated cells of the collecting tubules are important sites for H secretion and K reabsorption, but the collecting tubules are not highly permeable to urea. Furosemide acts mainly in the thick ascending LOH, and thiazide diuretics act mainly in the early distal tubule.

Guyton 13 ed. p 356-357

Question 42

Which of the following would be the most likely cause of hypernatremia associated with a small volume of highly concentrate urine (osmolarity = 1400 mOsm/L) in a patient with normal kidneys?
A. Primary aldosteronism
B. Diabetes mellitus
C. Diabetes insipidus
D. Dehydration due to insufficient water intake and heavy exercise.

Answer 42

D. Dehydration due to insufficient water intake and heavy exercise.

This would cause increase plasma sodium concentration, which would then stimulate release of ADH. This would increase water reabsorption in the distal and collecting tubules/ducts, causing a small volume of highly concentrated urine. Primary aldosteronism would be associated with sodium and water retention but normal renal excretion (equal to intake) of sodium and water after a few days. Uncontrolled diabetes mellitus is typically associated with large volumes of urine due to the osmotic diuresis associated with hyperglycemia. Diabetes insipidus is associated with large volumes of dilute urine.

Guyton 13 ed. p 439-440

Question 43

Which of the following has similar values for both intracellular and interstitial body fluids?
A. K ion concentration
B. Colloid osmotic pressure
C. Na ion concentration
D. Cl ion concentration 
E. Total osmolarity

Answer 43

E. Total osmolarity

Intracellular and extracellular body fluids have the same total osmolarity under steady-state conditions because the cell membrane is highly permeable to water. Therefore, water flows rapidly across the cell membrane until osmotic equilibrium is achieved. The colloid osmotic pressure is determined by the protein concentration, which is considerably higher inside the cell. The cell membrane is also relatively impermeable to K, Na, and Cl, and active transport mechs maintain low intracellular concentrations of sodium and chloride and a high intracellular concentration of potassium.

Guyton 13 ed. p 310-312

Question 44

Which of the following is true of the tubular fluid that passes through the lumen of the early distal tubule in the region of the macula densa?
A. It is usually isotonic.
B. It is usually hypotonic.
C. It is usually hyertonic.
D. It is hypertonic in antidiuresis.
E. It is hypertonic when the filtration rate of its own nephron decreases to 50% below normal.

Answer 44

B. It is usually hypotonic.

Fluid entering the early distal tubule is almost always hypotonic because sodium and other ions are actively transported out of the thick ascending LOH, whereas this portion of the nephron is virtually impermeable to water. For this reason, the thick ascending limb of the LOH and the early part of the distal tubule are often called the diluting segement.

Guyton 13 ed. p 354-355

Question 45

Which change tends to increase urinary calcium excretion?
A. Extracellular fluid volume expansion
B. Increased plasma parathyroid hormone concentration
C. Decreased blood pressure
D. Increased plasma phosphate concentration
E. Metabolic alkalosis

Answer 45

A. Extracellular fluid volume expansion

In the proximal tubule, Ca reabsorption usually parallels sodium and water reabsorption. With extracellular volume expansion or increased blood pressure, proximal sodium and water reabsorption is reduced, and a reduction in calcium reabsorption also occurs, causing increased urinary excretion of calcium. Increased parathyroid hormone, increased plasma phosphate concentration, and metabolic alkalosis all tend to decrease the renal excretion of calcium.

Guyton 13 ed. p 396-398

Question 46

What would tend to decrease GFR by more than 10% in a normal kidney?
A. Decrease in renal arterial pressure from 100 to 85 mm Hg
B. 50% decrease in afferent arteriolar resistance
C. 50% decrease in efferent arteriolar resistance
D 50% increase in the glomerular capillary filtration coefficient
E. Decrease in plasma colloid osmotic pressure from 28 to 20 mm Hg

Answer 46

C. 50% decrease in efferent arteriolar resistance

This would cause a large decrease in GFR - greater than 10%. A decrease in renal artery pressure from 100 to 85 mm Hg would cause only a slight decrease in GFR in a normal, autoregulating kidney. A decrease in afferent arteriole resistance, a decrease in plasma colloid osmotic pressure, or an increase in the glomerular capillary filtration coefficient would all tend to increase GFR.

Guyton 13 ed. p 337-340, 343

Question 47

Which statement is true?
A. ADH increases water reabsorption from the ascending LOH
B. Water reabsorption from the descending LOH is normally less than that from the ascending LOH
C. Na reabsorption from the ascending LOH is normally less than that from the descending LOH
D. Osmolarity of fluid in the early distal tubule would be less than 300 mOsm/L in a dehydrated patient with normal kidneys and increased ADH levels
E. ADH decreases the urea permeability in the medullary collecting tubules.

Answer 47

D. Osmolarity of fluid in the early distal tubule would be less than 300 mOsm/L in a dehydrated patient with normal kidneys and increased ADH levels

This is because the ascending limb of LOH and the early distal tubule are relatively impermeable to water, even in the presence of ADH. Therefore, the tubular fluid becomes progressively more dilute in these segments compared with plasma. ADH does not influence water reabsorption in the ascending limb of the LOH. The ascending limb, however, reabsorbs Na to a much greater extent than does the descending limb. Another important action of ADH is to increase the urea permeability in the medullary collecting ducts, which contributes to the hyperosmotic renal medullary interstitium in antidiuresis.

Guyton 13 ed. p 378-379

Question 48

Which would tend to increase Ca reabsorption in the renal tubule?
A. Extracellular fluid volume expansion
B. Increased plasma parathyroid hormone concentration
C. Increased blood pressure
D. Decreased plasma phosphate concentration
E. Metabolic acidosis

Answer 48

B. Increased plasma parathyroid hormone concentration

This would occur in the thick ascneding LOH and distal tubules. All others are associated with decreased Ca reabsoprtion by the renal tubules.

Guyton 13 ed. p 396-397

Question 49

At which renal tubular sites would the concentration of creatinine be expected to be highest in a normally hydrated person?
A. Same in all segments
B. Glomerular filtrate
C. End of the proximal tubule
D. End of the LOH
E. Distal tubule
F. Collecting duct

Answer 49

F. Collecting duct

This is because creatinine concentraion is progressively increased as water is reabsorbed along the renal tubular segments.

Guyton 13 ed. p 359

Question 50

Increases in both renal blood flow and GFR are caused by which mech?
A. Dilation of the afferent arterioles
B. Increased glomerular capillary filtration coefficient
C. Increased plasma colloid osmotic pressure
D. Dilation of the efferent arterioles

Answer 50

A. Dilation of the afferent arterioles

This lead to an increase in glomerular hydrostatic pressure and therefore an increase in GFR, as well as an increase in renal blood flow. Increased glomerular capillary filtration coefficient would also raise the GFR but would not be expected to alter renal blood flow. Increased plasma colloid osmotic pressure or dilation of the efferent arterioles would both tend to reduce GFR. Increased blood viscosity would tend to reduce blood flow and GFR.

Guyton 13 ed. P 337-341

Question 51

With a decrease in proteins (hypoproteinemia), anion gap may be
A. Increased
B. Decreased

Answer 51

B. Decreased

Question 52

Aldosterone site of action is
A. Collecting tubule and duct
B. Proximal tubule, thick ascending LOH/distal tubule, collecting tubule
C. Distal tubule/Collecting tubule and duct
D. Proximal tubule, thick ascending LOH/distal tubule

Answer 52

A. Collecting tubule and duct

Guyton 13 ed. p 362 Table 28-3

Question 53

Angiotensin II site of action is
A. Collecting tubule and duct
B. Proximal tubule, thick ascending LOH/distal tubule, collecting tubule
C. Distal tubule/Collecting tubule and duct
D. Proximal tubule, thick ascending LOH/distal tubule

Answer 53

B. Proximal tubule, thick ascending LOH/distal tubule, collecting tubule

Guyton 13 ed. p 362 Table 28-3

Question 54

Antidiuretic hormone site of action is
A. Collecting tubule and duct
B. Proximal tubule, thick ascending LOH/distal tubule, collecting tubule
C. Distal tubule/Collecting tubule and duct
D. Proximal tubule, thick ascending LOH/distal tubule

Answer 54

C. Distal tubule/Collecting tubule and duct

Guyton 13 ed. p 362 Table 28-3

Question 55

Atrial natriuretic peptide site of action is
A. Collecting tubule and duct
B. Proximal tubule, thick ascending LOH/distal tubule, collecting tubule
C. Distal tubule/Collecting tubule and duct
D. Proximal tubule, thick ascending LOH/distal tubule

Answer 55

C. Distal tubule/Collecting tubule and duct

Guyton 13 ed. p 362 Table 28-3

Question 56

Parathyroid hormone site of action is
A. Collecting tubule and duct
B. Proximal tubule, thick ascending LOH/distal tubule, collecting tubule
C. Distal tubule/Collecting tubule and duct
D. Proximal tubule, thick ascending LOH/distal tubule

Answer 56

D. Proximal tubule, thick ascending LOH/distal tubule

Guyton 13 ed. p 362 Table 28-3

Question 57

Which of the following lists ALL effects of aldosterone?
A. inc NaCl, H2O reabsorption, inc K secretion, inc H secretion
B. inc NaCl, H2O reabsorption, inc H secretion
C. inc H2O reabsorption
D. dec NaCl reabsorption
E. dec PO4 reabsorption, inc Ca reabsorption

Answer 57

A. inc NaCl, H2O reabsorption, inc K secretion, inc H secretion

Guyton 13 ed. p 362 Table 28-3

Question 58

Which of the following lists ALL effects of angiotensin II?
A. inc NaCl, H2O reabsorption, inc K secretion, inc H secretion
B. inc NaCl, H2O reabsorption, inc H secretion
C. inc H2O reabsorption
D. dec NaCl reabsorption
E. dec PO4 reabsorption, inc Ca reabsorption

Answer 58

B. inc NaCl, H2O reabsorption, inc H secretion

Guyton 13 ed. p 362 Table 28-3

Question 59

Which of the following lists ALL effects of antidiuretic hormone?
A. inc NaCl, H2O reabsorption, inc K secretion, inc H secretion
B. inc NaCl, H2O reabsorption, inc H secretion
C. inc H2O reabsorption
D. dec NaCl reabsorption
E. dec PO4 reabsorption, inc Ca reabsorption

Answer 59

C. inc H2O reabsorption

Guyton 13 ed. p 362 Table 28-3

Question 60

Which of the following lists ALL effects of atrial natriuretic peptide?
A. inc NaCl, H2O reabsorption, inc K secretion, inc H secretion
B. inc NaCl, H2O reabsorption, inc H secretion
C. inc H2O reabsorption
D. dec NaCl reabsorption
E. dec PO4 reabsorption, inc Ca reabsorption

Answer 60

D. dec NaCl reabsorption

Guyton 13 ed. p 362 Table 28-3

Question 61

Which of the following lists ALL effects of parathyroid hormone?
A. inc NaCl, H2O reabsorption, inc K secretion, inc H secretion
B. inc NaCl, H2O reabsorption, inc H secretion
C. inc H2O reabsorption
D. dec NaCl reabsorption
E. dec PO4 reabsorption, inc Ca reabsorption

Answer 61

E. dec PO4 reabsorption, inc Ca reabsorption

Guyton 13 ed. p 362 Table 28-3

Question 62

What are the two main functions of the macula densa?

Answer 62

1) It decreases resistance to blood flow in the afferent arterioles, which raises glomerular hydrostatic pressure and helps return GFR toward normal
2) It increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles, which are the major storage sites for renin.

The macula densa cells sense changes in volume delivery to the distal tubule by way of signals that are not completely understood.

Guyton 13 ed. p 343-344

Question 63

Where is the macula densa located?

Answer 63

initial portion of the distal tubule in close proximity to the afferent and efferent arterioles

Guyton 13 ed. p 343-344

Question 64

Where is the juxtaglomerular cells located?

Answer 64

in the walls of the afferent and efferent arterioles.

Guyton 13 ed. p 343-344