The prime driving force for counter current multiplier system is: (A) Medullary hyperosmolarity, (B) Reabsorption of Na+ in thick ascending limb, (C) Action of ADH via aquaporin channels, (D) Urea recycling
Answer is B. Ans. (b) Reabsorption of Na+ in thick ascending limb(Ref: Ganongy 25th ed/p.685)The primary driving force for counter current system is Reabsorption of Na+ in thick ascending limb through Na-K-2Cl cotransporter