Block 6 Renal Physio Prt 1
- 1.
Which of the following statements about renal potassium excretion is FALSE?
- A.
The secretion of K+ across the apical membrane of the collecting duct is passive.
- B.
About 75% of the excreted K+ is due to K+ filtered at the glomerulus
- C.
When aldosterone levels are high, the rate of K+ excretion will be high
- D.
Plasma aldosterone levels will rise in response to a rise in plasma K+ concentration
Correct Answer
B. About 75% of the excreted K+ is due to K+ filtered at the glomerulus -
- 2.
A decrease in dietary sodium intake
- A.
Will lead to a period of positive sodium balance where sodium accumulates in the body
- B.
Will normally cause a significant rise (e.g., >10 mOsm) in plasma osmolarity
- C.
Will result in the net loss of some water from the body.
- D.
All of the above
Correct Answer
C. Will result in the net loss of some water from the body.Explanation
A decrease in dietary sodium intake will result in the net loss of some water from the body. When sodium intake is reduced, the body tries to maintain a balance by excreting sodium through urine. This process requires water, leading to an increased loss of water from the body. Therefore, a decrease in dietary sodium intake will result in the net loss of some water from the body.Rate this question:
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- 3.
Which of the following statements about tubular sodium transport is FALSE?
- A.
Proximal tubular sodium reabsorption is regulated by angiotensin II.
- B.
In principle cells in the distal tubule, sodium uptake involves secondary active transport
- C.
Na+ and Cl− transport by the thick ascending limb makes the medullary interstitium hyperosmotic.
- D.
Diuretic drugs increase the excretion of sodium by reducing apical sodium uptake
Correct Answer
B. In principle cells in the distal tubule, sodium uptake involves secondary active transportExplanation
The statement that is FALSE is "In principle cells in the distal tubule, sodium uptake involves secondary active transport." The correct statement is that sodium uptake in the distal tubule does not involve secondary active transport.Rate this question:
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- 4.
A rise in the plasma ADH concentration
- A.
Will increase the water permeability of the apical membrane in the distal tubule and collecting ducts.
- B.
Will be triggered by a 5% reduction in blood volume
- C.
Will reduce the osmolarity of the excreted urine.
- D.
Will result in reduced cAMP levels in collecting duct principle cells.
Correct Answer
A. Will increase the water permeability of the apical membrane in the distal tubule and collecting ducts.Explanation
An increase in the plasma ADH concentration will lead to an increase in the water permeability of the apical membrane in the distal tubule and collecting ducts. This is because ADH, or antidiuretic hormone, acts on the cells of the distal tubule and collecting ducts to insert aquaporin channels into the apical membrane. These aquaporin channels allow water to pass through the membrane and be reabsorbed back into the bloodstream, resulting in a decrease in urine output and an increase in water reabsorption.Rate this question:
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- 5.
A rise in the plasma aldosterone concentration
- A.
Will cause the afferent arteriole to dilate
- B.
Will increase the apical-membrane potassium permeability in principle cells the collecting ducts
- C.
Will directly inhibit renin release.
- D.
Will occur in response to a decrease in the plasma angiotensin II concentration.
Correct Answer
B. Will increase the apical-membrane potassium permeability in principle cells the collecting ductsExplanation
An increase in plasma aldosterone concentration will increase the apical-membrane potassium permeability in principal cells of the collecting ducts. Aldosterone acts on the principal cells of the collecting ducts to increase the reabsorption of sodium ions and the secretion of potassium ions. This leads to an increase in potassium permeability in the apical membrane of these cells, allowing more potassium ions to be secreted into the urine. This helps to maintain electrolyte balance in the body.Rate this question:
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- 6.
Which of the following will not influence renal renin secretion?
- A.
A change in renal sympathetic nervous system activity.
- B.
A rise in the plasma angiotensin II concentration.
- C.
A change in the flow rate of tubular fluid past the macula densa segment.
- D.
None of the above (since all can influence renin secretion).
Correct Answer
D. None of the above (since all can influence renin secretion).Explanation
The correct answer is "None of the above (since all can influence renin secretion)". This means that all of the options listed in the question will influence renal renin secretion. A change in renal sympathetic nervous system activity can stimulate renin secretion, as can a rise in the plasma angiotensin II concentration. Additionally, a change in the flow rate of tubular fluid past the macula densa segment can also affect renin secretion. Therefore, none of the options provided will not influence renal renin secretion.Rate this question:
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- 7.
Which of the following statements about atrial naturetic peptide (ANP) is FALSE?
- A.
ANP is secreted by the cardiac atria in response to increased stretch
- B.
ANP will increase GFR by dilating the afferent arteriole
- C.
ANP will not affect the secretion of renin
- D.
ANP reduces the Na+ permeability of the apical membrane of inner medullary collecting-duct cells.
Correct Answer
C. ANP will not affect the secretion of reninExplanation
ANP is a hormone secreted by the cardiac atria in response to increased stretch. It acts as a vasodilator and increases the glomerular filtration rate (GFR) by dilating the afferent arteriole. ANP also inhibits the secretion of renin, which is responsible for regulating blood pressure and fluid balance. Therefore, the statement that ANP will not affect the secretion of renin is false.Rate this question:
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- 8.
The process of countercurrent multiplication in the renal medulla
- A.
Is a passive process that occurs in the vasa recta
- B.
Will not be affected by inhibition of ascending-limb sodium transport
- C.
Will result in the excretion of hypotonic urine when ADH levels are low
- D.
Does not involve the descending limb of Henle's loop
Correct Answer
C. Will result in the excretion of hypotonic urine when ADH levels are lowExplanation
The process of countercurrent multiplication in the renal medulla refers to the exchange of solutes and water in the loop of Henle and vasa recta. This process is responsible for creating a concentration gradient in the medulla, which allows for the reabsorption of water and the excretion of concentrated urine when ADH levels are high. However, when ADH levels are low, countercurrent multiplication will result in the excretion of hypotonic urine, as less water is reabsorbed and more solutes are excreted. This is because the concentration gradient in the medulla is not maintained without the presence of ADH.Rate this question:
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- 9.
The plasma − HCO3 concentration is 45 meq/L and PCO2 is 50 mmHg. Which of the following values is closest to the plasma pH?
- A.
6.8
- B.
7.1
- C.
7.4
- D.
7.6
Correct Answer
D. 7.6Explanation
Based on the given information, the plasma bicarbonate (HCO3) concentration is 45 meq/L and the partial pressure of carbon dioxide (PCO2) is 50 mmHg. These values suggest a respiratory acidosis, which is characterized by an increase in PCO2 and a decrease in pH. Since the pH is inversely related to the PCO2, a higher PCO2 value would result in a lower pH. Therefore, the closest value to the plasma pH would be 7.1.Rate this question:
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- 10.
The plasma − HCO3 concentration is 14 meq/L, blood PCO2 is 30 mmHg and blood pH is 7.3. Based on these values, which of the following best describes the acid-base status of this person?
- A.
Metabolic acidosis
- B.
Metabolic alkalosis
- C.
Respiratory alkalosis
- D.
Respiratory acidosis
Correct Answer
A. Metabolic acidosisExplanation
Based on the given values, the plasma HCO3 concentration is low (14 meq/L), indicating a decrease in bicarbonate levels. Additionally, the blood pH is below the normal range (7.3), indicating acidemia. These findings suggest a metabolic acidosis, which is characterized by a decrease in bicarbonate levels and an increase in acidity.Rate this question:
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- 11.
Hydrogen-ion secretion by renal tubular cells
- A.
Will rise in response to a fall in the plasma bicarbonate concentration.
- B.
Will result in the release of bicarbonate into plasma.
- C.
Will be reduced by inhibition of cytosolic carbonic anhydrase.
- D.
All of the above.
Correct Answer
D. All of the above.Explanation
The correct answer is "All of the above." This means that all three statements mentioned in the options are true. Hydrogen-ion secretion by renal tubular cells will indeed rise in response to a fall in the plasma bicarbonate concentration. It will also result in the release of bicarbonate into plasma. Additionally, hydrogen-ion secretion will be reduced by the inhibition of cytosolic carbonic anhydrase.Rate this question:
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- 12.
Vitamin D
- A.
Is converted into calcitriol in the kidney in response to an elevated plasma phosphate concentration
- B.
Activation to calcitriol in the kidney is suppressed by PTH.
- C.
In its activated form stimulates gastrointestinal calcium and phosphate absorption
- D.
Levels are suppressed when the plasma calcium concentration is low.
Correct Answer
C. In its activated form stimulates gastrointestinal calcium and phosphate absorptionExplanation
Vitamin D, when converted into its activated form called calcitriol in the kidney, stimulates the absorption of calcium and phosphate in the gastrointestinal tract. This means that when vitamin D is activated, it helps the body absorb more calcium and phosphate from the food we eat. This is important for maintaining healthy levels of these minerals in the body, which are essential for bone health and other physiological processes.Rate this question:
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- 13.
Which of the flowing statements about calcium and phosphate metabolism is FALSE?
- A.
PTH increases renal calcium excretion and decreases renal phosphate excretion.
- B.
Release of calcium and phosphate from bone increases when osteoclasts are stimulated by PTH.
- C.
A calcium phosphate precipitate can be formed when the concentration of either ion rises substantially.
- D.
A fall in plasma phosphate levels can indirectly lead to a decrease in PTH secretion.
Correct Answer
A. PTH increases renal calcium excretion and decreases renal phosphate excretion. -
- 14.
Patients with renal insufficiency (GFR <25% of normal) often need to restrict their K+ intake because they are prone to hyperkalemia. Based upon what we have discussed in class, what would be the most probable explanation for the limited ability of these patients to excrete K+?
- A.
The low GFR reduces the filtered load of potassium.
- B.
Because K+ secretion is passive, the ability to secrete K+ depends on the total amount of tubular fluid that enters the distal tubules, and this is greatly reduced in these patients.
- C.
Renal K+ excretion is reduced by diuretics like furosemide that are often prescribed for these patients.
- D.
None of the above is a reasonable explanation
Correct Answer
B. Because K+ secretion is passive, the ability to secrete K+ depends on the total amount of tubular fluid that enters the distal tubules, and this is greatly reduced in these patients.Explanation
The limited ability of patients with renal insufficiency to excrete K+ is most likely due to the reduced amount of tubular fluid that enters the distal tubules. Since K+ secretion is a passive process, the total amount of tubular fluid entering the distal tubules determines the ability to secrete K+. In patients with low GFR, the filtered load of potassium is reduced, leading to a limited ability to excrete K+.Rate this question:
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- 15.
Bilateral renal-artery stenosis is a condition where both of the renal arteries are sufficiently constricted so that renal blood flow is reduced. What effect would this have on mean arterial blood pressure (BP)?
- A.
BP will rise because the pressure in the afferent arteriole will be reduced, thereby stimulating renin release and angiotensin II production.
- B.
BP will rise because aldosterone secretion will increase because of the high angiotensin II levels.
- C.
BP will rise because extracellular fluid volume will increase.
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
This is because bilateral renal-artery stenosis leads to reduced renal blood flow, which triggers the release of renin and production of angiotensin II. Angiotensin II causes vasoconstriction, leading to increased mean arterial blood pressure. Additionally, high levels of angiotensin II stimulate aldosterone secretion, which increases sodium and water reabsorption, leading to an increase in extracellular fluid volume. Therefore, all of the given options contribute to the rise in mean arterial blood pressure in cases of bilateral renal-artery stenosis.Rate this question:
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Mar 21, 2023Quiz Edited by
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Mar 24, 2012Quiz Created by
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