Physiology MCQs Kidney And Answers

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1. Glomerular filtration rate (GFR) would be increased by:
a) Constriction of the afferent arteriole
b) A decrease in afferent arteriolar pressure
c) Compression of the renal capsule
d) A decrease in the concentration of plasma protein
e) A decrease in renal blood flow
Ans. D
REVISION NOTES:
• The rate at which plasma is filtered (measured in ml/min) is known as the glomerular filtration rate (GFR)
• The primary driving force for GFR is glomerular capillary pressure opposed by fluid pressure in Bowman’s capsule and colloid osmotic pressure due to plasma proteins.
• With fewer plasma proteins, the plasma has lower than normal colloid osmotic pressure. With less colloid osmotic pressure opposing GFR, GFR increases

2. The greatest amount of hydrogen ion secreted by the proximal tubule is associated with
a) Excretion of potassium ion
b) Excretion of hydrogen ion
c) Reabsorption of calcium ion
d) Reabsorption of bicarbonate ion
e) Reabsorption of phosphate ion
Ans. D
REVISION NOTES:
• The proximal tubule regulates the pH of the filtrate by exchanging hydrogen ions in the interstitium for bicarbonate ions in the filtrate; it is also responsible for secreting organic acids, such as creatinine and other bases, into the filtrate.
• Hydrogen ions secreted combine with filtered HCO3- ions to form carbonic acid and then CO2 + H2O, which are then passively reabsorbed

3. Most of the glucose that is filtered through the glomerulus undergoes reabsorption in the:
a) Proximal tubule
b) Descending limp of the loop of Henle
c) Ascending limb of the loop of Henle
d) Distal tubule
e) Collecting duct
Ans. A
REVISION NOTES:
• Approximately, 80% of the glomerular filtrate is reabsorbed in the proximal tubule.
• By the time the filtrate has reached the mid part of the proximal tubule, 100% of the filtered glucose and amino acids have been reabsorbed

4. Which of the following substances will be more concentrated at the end of the proximal tubule than at the beginning of the proximal tubule?
a) Glucose
b) Creatinine
c) Sodium
d) Bicarbonate
e) Amino acids
Ans. B (Creatinine)
REVISION NOTES:
• Creatinine is freely filtered by the glomerulus, but also actively secreted by the proximal tubule from the peritubular capillaries in small amounts
• Therefore, creatinine concentration will be slightly higher at the end of the proximal tubule that at the beginning of the proximal tubule

5. In the distal tubules, sodium reabsorption is increased directly by increased:
a) Sympathetic nerve stimulation of the kidney
b) Atrial natriuretic hormone secretion
c) Antidiuretic hormone secretion
d) Aldosterone secretion
e) Angiotensin secretion
Ans. D
REVISION NOTES:
• The DCT reabsorbs roughly 5%–10% of the filtered sodium load. The remaining 10% is reabsorbed in the distal tubule. The reabsorption of sodium from here and the collecting ducts is under hormonal control allowing.
• Aldosterone stimulates sodium reabsorption in this segment of the nephron
• Aldosterone is a steroid hormone that is released from the adrenal gland in response to volume depletion or hyperkalemia

6. The glomerular filtration rate will increase if:
a) Circulating blood volume increase
b) The afferent arteriolar resistance increases
c) The efferent arteriolar resistance decreases
d) The plasma protein concentration decreases
Ans. D
REVISION NOTES:
• The rate at which kidneys filter blood is called the glomerular filtration rate.
• The primary driving force for GFR is glomerular capillary pressure opposed by fluid pressure in Bowman’s capsule and colloid osmotic pressure due to plasma proteins. With fewer plasma proteins, the plasma has lower than normal colloid osmotic pressure. With less colloid osmotic pressure opposing GFR, GFR increases

7. Hydrostatic pressure in renal glomerular capillaries
a. Is lower than pressure in efferent arterioles
b. Rises when afferent arterioles constrict
c. Is higher than in most capillaries at heart level
d. Falls by 10 per cent when arterial pressure falls by 10 per cent
e. Falls along the length of the capillary
REVISION NOTES:
A. False – It must be higher to maintain blood flow.
B. False – The pressure drop across the afferent arterioles increases as they constrict.
C. True – The afferent arterioles offer relatively little resistance.
D. False – Redistribution of renal vascular resistance due to autoregulation tends to maintain glomerular hydrostatic pressure and hence filtration.
E. True – Hydrostatic pressure falls due to vascular resistance; oncotic pressure rises due to loss of protein-poor filtrate; both these factors reduce filtration pressure along the length of the glomerular capillary.

8. In fluid in the distal part of the proximal convoluted tubule
a. Urea concentration is higher than in Bowman’s capsule.
b. pH is less than 6 when the kidneys are excreting an acid urine.
c. Glucose concentration is similar to that in plasma.
d. Osmolality is about 25 per cent that of glomerular filtrate.
e. Bicarbonate concentration is lower than in plasma.
REVISION NOTES:
A. True – Due to reabsorption of water
B. False – Acidification occurs mainly in the distal convoluted tubule.
C. False – Most or all of the glucose is reabsorbed before the end of the proximal tubule.
D. False – Osmolality changes little in the proximal convoluted tubule.
E. True – Like glucose, HCO3 is usually completely reabsorbed in the proximal tubule.

9. Renal tubules normally reabsorb
a. More water every hour than the entire plasma volume
b. All filtered HCO3 in respiratory acidosis.
c. All filtered amino acids.
d. All filtered plasma proteins.
e. More K than Cl
REVISION NOTES:
A. True – About 99 per cent of the glomerular filtrate (about 8 liters/hour).
B. True – This plus HCO3 manufactured in the kidney compensates the respiratory acidosis.
C. True – These are filtered but do not appear in normal urine.
D. True – Again, some are filtered but do not appear in urine.
E. False – About 20 times as much chloride as potassium is filtered (this is the ratio of their plasma concentrations)

10. In the nephron, the osmolality of fluid in the
a. Tip of the loop of Henle is less than that of plasma.
b. Bowman’s capsules is less than that in the distal tubules.
c. Collecting duct rises when vasopressin is being secreted.
c. Proximal convoluted tubule rises along its length.
d. Medullary interstitium can exceed one osmole per liter
REVISION NOTES:
A. False – This fluid is hypertonic because of counter-current concentration.
B. False – Distal tubular fluid is hypotonic.
C. True – Vasopressin (ADH) promotes water, but not salt, reabsorption in collecting ducts.
D. False – The fluid remains isotonic with plasma.
E. True – It can be about four times that of plasma

11. The cells of the distal convoluted tubule
a. Reabsorb about 50 per cent of the water filtered by the glomeruli
b. Secrete hydrogen ions into the tubular lumen
c. Form NH4 ions
d. Reabsorb sodium in exchange for hydrogen or potassium ions
e. Determine the final composition of urine.
REVISION NOTES:
A. False – About 80 per cent of the filtered water is reabsorbed before it reaches the distal tubules.
B. True – The rate is related to acid–base requirements.
C. True – By conversion of glutamine to glutamate; NH3 is a buffer for the H being excreted.
D. True – H secretion is related to the body’s acid–base balance.
E. False – Further modification takes place in the collecting ducts

12. The cells of the distal convoluted tubule
A. Reabsorb about 50 per cent of the water filtered by the glomeruli.
B. Secrete hydrogen ions into the tubular lumen.
C. Form NH4+ ions
D. Reabsorb sodium in exchange for hydrogen or potassium ions.
E. Determine the final composition of urine.
REVISION NOTES
A. False – About 80 per cent of the filtered water is reabsorbed before it reaches the distal tubules.
B. True – The rate is related to acid–base requirements.
C. True – By conversion of glutamine to glutamate; NH3 is a buffer for the H being excreted.
D. True – H secretion is related to the body’s acid–base balance.
E. False – Further modification takes place in the collecting ducts.

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