Concentration of Filtrate (Counter-current) — NEET Biology MCQs with Solutions
Free NEET Biology Concentration of Filtrate (Counter-current) MCQs with step-by-step solutions (23 questions). Part of Excretory Products and Their Elimination. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Concentration of Filtrate (Counter-current) · easy
Mammals have the ability to produce ______ urine.
A. Alkaline
B. Hypotonic
C. Isotonic
D. Hypertonic ✓ Correct
Solution: Mammals, with their well-developed loop of Henle and counter-current mechanism, can produce a concentrated (hypertonic) urine.
Q2 — Concentration of Filtrate (Counter-current) · easy
Which one plays an important role in the counter-current mechanism?
A. Loop of Henle
B. PCT
C. Vasa recta
D. Both (1) and (3) ✓ Correct
Solution: The counter-current mechanism involves both the loop of Henle and the vasa recta, which run parallel to each other.
Q3 — Concentration of Filtrate (Counter-current) · medium
In which of the following does the counter current operate?
A. In ascending limb of loop of Henle
B. In ascending limb or descending limb of vasa recta
C. In descending limb of loop of Henle
D. Between the 2 limbs of Henle's loop and those of vasa recta ✓ Correct
Solution: The counter current operates between the two limbs of Henle's loop and between the two limbs of the vasa recta, maintaining the medullary gradient.
Q4 — Concentration of Filtrate (Counter-current) · hard
The medullary gradient is developed by all the following except:
A. Diffusion of small amount of urea from collecting duct into medullary interstitium
B. Proximity between Henle's loop and vasa recta as well as the counter-current in them
C. Reabsorption of Na+ from ascending limb of Henle's loop into medullary interstitium
D. Reabsorption of Na+ from descending limb of Henle's loop ✓ Correct
Solution: The descending limb of Henle's loop is impermeable to salt (it only loses water), so Na+ is not reabsorbed from it; NaCl is transported out of the ascending limb.
Q5 — Concentration of Filtrate (Counter-current) · easy
The medullary gradient is mainly caused by:
A. H+ and K+
B. NaCl and Urea ✓ Correct
C. Urea and H+
D. Urea & K+
Solution: The osmotic (medullary) concentration gradient is mainly caused by NaCl and urea.
Q6 — Concentration of Filtrate (Counter-current) · medium
The counter-current mechanism helps to maintain a concentration gradient. This gradient helps in:
A. Easy passage of water from medullary interstitial fluid to collecting tubule and thereby diluting urine
B. Inhibition of passage of water between the collecting tubule and medulla and so isotonic urine is formed
C. Easy passage of water from medulla to collecting tubule and thereby concentrating urine
D. Easy passage of water from collecting tubule and thereby concentrating urine ✓ Correct
Solution: The medullary gradient draws water out of the collecting duct/tubule into the interstitium, thereby concentrating the urine.
Q7 — Concentration of Filtrate (Counter-current) · hard
NaCl is transported by the ascending limb of Henle's loop which is exchanged with:
A. Ascending limb of vasa recta
B. DCT
C. PCT
D. Descending limb of vasa recta ✓ Correct
Solution: NaCl transported out by the ascending limb of Henle's loop is exchanged with (taken up by) the descending limb of the vasa recta.
Q8 — Concentration of Filtrate (Counter-current) · hard
NaCl is returned to the ______ by the ascending limb of vasa recta.
A. Interstitial fluid of medulla ✓ Correct
B. PCT
C. Ascending limb of Henle's loop
D. DCT
Solution: The ascending limb of the vasa recta returns NaCl to the interstitial fluid of the medulla, helping maintain the concentration gradient.
Q9 — Concentration of Filtrate (Counter-current) · easy
The human kidney can produce urine nearly how many times concentrated than the initial filtrate formed?
A. 2
B. 10
C. 100
D. 4 ✓ Correct
Solution: The human kidney can produce urine about four times concentrated than the initial filtrate.
Q10 — Concentration of Filtrate (Counter-current) · hard
The high osmolarity of the renal medulla is maintained by all of the following, except:
I. Diffusion of salt from the ascending limb of the loop of Henle
II. Active transport of salt from the upper region of the ascending limb
III. The spatial arrangement of juxtamedullary nephrons
IV. Diffusion of urea from the collecting duct
V. Diffusion of salt from the descending limb of the loop of Henle
A. III and IV
B. Only V ✓ Correct
C. I and V
D. Only I
Solution: The descending limb of Henle's loop is impermeable to salt and does not release salt, so option V does not contribute to medullary osmolarity.
Q11 — Concentration of Filtrate (Counter-current) · medium
Assertion: The descending limb of the loop of Henle concentrates the filtrate. Reason: It is permeable to water but almost impermeable to electrolytes.
A. Assertion is false, but Reason is true.
B. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. ✓ Correct
C. Assertion is true, but Reason is false.
D. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
Solution: Water leaving while electrolytes stay makes the descending limb concentrate the filtrate.
Q12 — Concentration of Filtrate (Counter-current) · medium
Assertion: The ascending limb of the loop of Henle dilutes the filtrate. Reason: It is impermeable to water but allows the transport of electrolytes.
A. Assertion is true, but Reason is false.
B. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. ✓ Correct
C. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
D. Assertion is false, but Reason is true.
Solution: Electrolytes leaving while water stays makes the ascending limb dilute the filtrate.
Q13 — Concentration of Filtrate (Counter-current) · hard
Assertion: The counter current mechanism helps maintain a concentration gradient in the medullary interstitium. Reason: This gradient is mainly caused by NaCl and urea.
A. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
B. Assertion is true, but Reason is false.
C. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. ✓ Correct
D. Assertion is false, but Reason is true.
Solution: The gradient maintained by the counter current mechanism is indeed produced by NaCl and urea.
Q14 — Concentration of Filtrate (Counter-current) · hard
Assertion: Some amount of urea may be retained in the kidney matrix of ureotelic animals. Reason: This is done to maintain the desired osmolarity within the kidney.
A. Assertion is false, but Reason is true.
B. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. ✓ Correct
C. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
D. Assertion is true, but Reason is false.
Solution: Urea is retained in the medullary matrix specifically to maintain the required osmolarity.
Q15 — Concentration of Filtrate (Counter-current) · hard
Assertion: NaCl is transported by the ascending limb of the loop of Henle and exchanged with the descending limb of vasa recta. Reason: NaCl is returned to the interstitium by the ascending portion of the vasa recta.
A. Assertion is true, but Reason is false.
B. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
C. Assertion is false, but Reason is true.
D. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. ✓ Correct
Solution: Both statements about NaCl movement are true, but the reason is not the direct explanation of the assertion.
Q16 — Concentration of Filtrate (Counter-current) · hard
Assertion: Mammals have the ability to produce a highly concentrated urine. Reason: The Henle's loop and vasa recta play a significant role in the counter current mechanism.
A. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. ✓ Correct
B. Assertion is true, but Reason is false.
C. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
D. Assertion is false, but Reason is true.
Solution: The counter current action of Henle's loop and vasa recta is what enables highly concentrated urine.
Q17 — Concentration of Filtrate (Counter-current) · medium
Statement 1: The descending limb of the loop of Henle is permeable to electrolytes. Statement 2: The ascending limb of the loop of Henle is permeable to water.
A. Statement 1 is correct but Statement 2 is incorrect.
B. Both Statement 1 and Statement 2 are correct.
C. Statement 1 is incorrect but Statement 2 is correct.
D. Both Statement 1 and Statement 2 are incorrect. ✓ Correct
Solution: The descending limb is impermeable to electrolytes and the ascending limb is impermeable to water, so both statements are incorrect.
Q18 — Concentration of Filtrate (Counter-current) · hard
Statement 1: The counter current mechanism is facilitated by the arrangement of Henle's loop and vasa recta. Statement 2: Osmolarity increases from 300 mOsmol/L in the cortex to 1200 mOsmol/L in the inner medulla.
A. Statement 1 is incorrect but Statement 2 is correct.
B. Both Statement 1 and Statement 2 are incorrect.
C. Statement 1 is correct but Statement 2 is incorrect.
D. Both Statement 1 and Statement 2 are correct. ✓ Correct
Solution: The counter-current mechanism relies on the loop of Henle and vasa recta and the medullary gradient rises from 300 to 1200 mOsmol/L, so both are correct.
Q19 — Concentration of Filtrate (Counter-current) · medium
Regarding the "Loop of Henle," find the correct statements:
A. Reabsorption in this segment is minimum.
B. Descending limb is permeable to electrolytes.
C. Ascending limb is impermeable to water.
D. Descending limb concentrates the filtrate.
E. Ascending limb allows transport of electrolytes actively or passively.
A. A, B, C and E are correct
B. All except A are correct
C. A, C, D and E are correct ✓ Correct
D. B, C and D are correct
Solution: Reabsorption here is minimal (A), the ascending limb is impermeable to water (C), the descending limb concentrates the filtrate (D), and the ascending limb transports electrolytes (E); the descending limb is impermeable to electrolytes, so B is false.
Q20 — Concentration of Filtrate (Counter-current) · hard
Find the correct statements regarding "Counter Current Mechanism":
A. Facilitated by Henle's loop and Vasa recta.
B. Flow of filtrate in the two limbs of Henle's loop is in opposite directions.
C. Flow of blood through the two limbs of vasa recta is in the same direction.
D. It maintains an increasing osmolarity towards the inner medulla.
E. NaCl and Urea are the main components maintaining this gradient.
A. C, D and E are correct
B. A, B, D and E are correct ✓ Correct
C. All are correct
D. A, B and C are correct
Solution: It is facilitated by Henle's loop and vasa recta (A), filtrate flows in opposite directions in the two limbs (B), osmolarity increases toward the inner medulla (D), and NaCl and urea maintain the gradient (E); vasa recta blood also flows counter-currently, so C is false.
Q21 — Concentration of Filtrate (Counter-current) · hard
Identify the correct statements regarding the "Descending limb of Henle's loop":
A. It is permeable to water.
B. It is almost impermeable to electrolytes.
C. It dilutes the filtrate as it moves down.
D. It helps in maintaining high osmolarity of medullary interstitial fluid.
E. It is lined by brush border epithelium.
A. All except E are correct
B. A, B and D are correct ✓ Correct
C. B, C and D are correct
D. A, C and E are correct
Solution: The descending limb is permeable to water (A), almost impermeable to electrolytes (B), and helps maintain high medullary osmolarity (D); it concentrates rather than dilutes the filtrate and has no brush border, so C and E are false.
Q22 — Concentration of Filtrate (Counter-current) · hard
Regarding the "Collecting Duct", which statements are correct?
A. Large amounts of water could be reabsorbed from this region.
B. It extends from the cortex of the kidney to the inner parts of the medulla.
C. It allows passage of small amounts of urea into the medullary interstitium.
D. It plays a role in maintaining the pH of blood.
E. It is completely impermeable to all salts.
A. B, D and E are correct
B. A, C and E are correct
C. All are correct
D. A, B, C and D are correct ✓ Correct
Solution: The collecting duct reabsorbs large amounts of water (A), extends from cortex to inner medulla (B), passes small amounts of urea into the interstitium (C), and helps maintain blood pH (D); it is not impermeable to all salts, so E is false.
Q23 — Concentration of Filtrate (Counter-current) · hard
Regarding "Vasa Recta", select the correct statements:
A. It is a 'U' shaped capillary network.
B. It is highly developed in cortical nephrons.
C. It runs parallel to the Henle's loop.
D. It carries blood in a counter-current pattern relative to the filtrate flow.
E. It is absent or highly reduced in majority of nephrons.
A. All are correct
B. A, C, D and E are correct ✓ Correct
C. B, D and E are correct
D. A, B and C are correct
Solution: Vasa recta is U-shaped (A), runs parallel to Henle's loop (C), carries blood counter-currently (D), and is absent or reduced in the majority (cortical) nephrons (E); it is well developed only in juxtamedullary nephrons, so B is false.