This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Mechanism of Concentration of the Filtrate”.
1. Which of the following plays a significant role in the concentration of urine?
a) Henle’s loop and vasa recta
b) PCT and DCT
c) Glomerulus and Bowman’s capsule
d) Collecting duct and tubule
Explanation: Mammals can produce concentrated urine. The Henle’s loop and vasa recta present in the mammals play a significant role in the concentration of the urine.
2. What is meant by counter-current?
a) When blood flows in the opposite direction in two limbs of the Henle’s loop
b) When the blood flows in the same direction in two limbs of the Henle’s loop
c) When the blood does not flow through any of the limbs of Henle’s loop
d) When some blood flows in Henle’s loop and the other blood flows in the vasa recta
Explanation: As the flow of filtrate in the two limbs of Henle’s loop is in opposite directions, therefore it forms a counter current. The flow of blood through the two limbs of the vasa recta is also in a counter-current pattern.
3. What is the significance of the proximity of Henle’s loop and vasa recta?
a) Maintains osmolarity
b) Maintains the concentration of only water
c) For reabsorption of nutrients
d) No proximity at all
Explanation: The proximity between the Henle’s loop and vasa recta, as well as the counter-current in them, help in maintaining an increasing osmolarity towards the inner medullary interstitium.
4. What is the osmolarity of the urine in the cortex?
a) 300 mOsmol/L
b) 600 mOsmol/L
c) 900 mOsmol/L
d) 1200 mOsmol/L
Explanation: The osmolarity of the filtrate in the cortex is about 300 mOsmol/L while in the inner medulla it is 1200 mOsmol/L. In the inner medulla, urine is four times more concentrated than the initial filtrate.
5. The gradient of osmolarity is mainly caused by NaCl.
Explanation: The osmotic gradient is mainly caused by NaCl and urea. NaCl is transported by the ascending limb of Henle’s loop which is exchanged with the descending limb of the vasa recta.
6. Which of the following returns NaCl into the interstitium?
a) Ascending loop of Henle
b) Descending loop of Henle
c) Ascending portion of the vasa recta
d) Descending portion of the vasa recta
Explanation: NaCl is returned to the interstitium by the ascending portion of the vasa recta. Just like NaCl, small amounts of urea are also transported back to the interstitial fluid by the collecting tubule.
7. Which of the following structure make the countercurrent mechanism?
a) Henle’s loop and glomerulus
b) PCT and DCT
c) Henle’s loop and vasa recta
d) Vasa recta and collecting duct
Explanation: The specialized arrangement of Henle’s loop and vasa recta which enhances the transport of substances and helps in concentrating the urine is known as counter-current mechanism.
8. Which of the following is not a feature of a counter-current mechanism?
a) Helps in maintaining the concentration gradient
b) Helps in making the passage of water easier
c) Helps in concentrating the urine
d) Helps in diluting the urine
Explanation: Countercurrent mechanism helps to maintain a concentration gradient in the medullary interstitium. The presence of such an interstitial gradient helps in easy passage of water from the collecting tubule and therefore helps in concentrating the urine.
9. Which of the following are not involved in the monitoring of kidneys?
Explanation: The functioning of the kidneys is efficiently monitored and regulated by the hormonal feedback mechanisms involving the hypothalamus, JGA, and to a certain extent, the heart.
10. Osmoreceptors in the body is not directly activated by which of the following?
a) Ionic concentration
b) Blood volume
c) Body fluid volume
d) Blood pressure
Explanation: Osmoreceptors in the body are directly activated by changes in the blood volume, body fluid volume, and ionic concentration. An excessive loss of fluid from the body can activate these receptors.
11. The hypothalamus releases vasopressin from the adenohypophysis.
Explanation: An excessive loss of body fluid stimulates the hypothalamus to release antidiuretic hormone or vasopressin from the neurohypophysis. ADH stimulates the reabsorption of water from the latter parts of the renal tubule.
12. What will happen if the blood volume increases?
a) Switch off the osmoreceptors
b) Osmoreceptors get activated
c) Osmoreceptors get permanently deactivated
d) Osmoreceptors do not play a significant role
Explanation: An increase in the body fluid volume or the blood volume can switch off the osmoreceptors and suppress the ADH release to complete the feedback.
13. What is ADH?
Explanation: ADH affects the kidney function by its constrictory effects on the blood vessels as it is a vasoconstrictor. This causes an increase in the blood pressure which further increases the GFR.
14. Which of the following is released by JG cells when GFR falls its normal levels?
Explanation: A fall in the GFR can activate the JG cells to produce renin which converts angiotensinogen in the blood to angiotensin I and further to angiotensin II which is a powerful vasoconstrictor itself and increases the GFR.
15. Which of the following is responsible for the secretion of ANF?
Explanation: An increase in blood flow to the atria of the heart can cause the release of Atrial Natriuretic factor or ANF which causes vasodilation and therefore decreases the blood pressure.
Sanfoundry Global Education & Learning Series – Biology – Class 11.
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