PHGY 214 Lecture Notes - Lecture 4: Aquaporin, Cyclic Adenosine Monophosphate, Diuretic
12 May 2016
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Document Summary
Is responsible for 25% of na, and 15% of water reabsorbed by the kidney. There is a high na concenteation in urine (up to 1200mm); however, the na/k atpase can only pump against a 200mm gradient. The loop of henle creates an osmotic gradient in the kidney isf. The countercurrent multiplier effect is created by combining a loop structure with different permeabilities to na and water in different parts of the loop. The effect is that the osmotic gradient is multiplied. The descending loop is permeable to water and impermeable to na. The ascending loop is permeable to na and impermeable to water: describe the changes in osmolarity of the filtrate as it proceeds through the nephron (proximal tubule, loop of henle, distal tubule, collecting duct). Initially, the medulla isf concentration is uniformly 300mosm/l. The active nacl pump in the ascending loop transports nacl out of the lumen until the. Isf is 200mosm/l, which makes the fluid hypertonic.
