answer is A
my question is why would B be wrong? if the sodium ion concentration increases then the water would diffuse there
The main function of ADH is to conserve water in the bloodstream and reduce it in the urine to prevent dehydration. So when water moves in the direction of arrow 1, it is escaping the duct into the blood stream. H̶o̶w̶e̶v̶e̶r̶ i̶n̶ B̶, i̶f̶ t̶h̶e̶ s̶o̶d̶i̶u̶m̶ c̶o̶n̶c̶e̶n̶t̶r̶a̶t̶i̶o̶n̶ i̶n̶c̶r̶e̶a̶s̶e̶d̶ i̶n̶s̶i̶d̶e̶ t̶h̶e̶ d̶u̶c̶t̶, t̶h̶e̶n̶ w̶a̶t̶e̶r̶ w̶i̶l̶l̶ m̶o̶v̶e̶ i̶n̶ t̶h̶e̶ d̶i̶r̶e̶c̶t̶i̶o̶n̶ o̶f̶ t̶h̶e̶ h̶i̶g̶h̶e̶r̶ c̶o̶n̶c̶e̶n̶t̶r̶a̶t̶i̶o̶n̶ t̶h̶u̶s̶ m̶o̶r̶e̶ w̶a̶t̶e̶r̶ w̶i̶l̶l̶ e̶n̶t̶e̶r̶ t̶h̶e̶ d̶u̶c̶t̶ f̶r̶o̶m̶ t̶h̶e̶ b̶l̶o̶o̶d̶s̶t̶r̶e̶a̶m̶, t̶h̶e̶r̶e̶f̶o̶r̶e̶ c̶a̶u̶s̶i̶n̶g̶ d̶e̶h̶y̶d̶r̶a̶t̶i̶o̶n̶ a̶s̶ i̶t̶ w̶i̶l̶l̶ t̶h̶e̶n̶ b̶e̶ r̶e̶l̶e̶a̶s̶e̶d̶ a̶l̶o̶n̶g̶ w̶i̶t̶h̶ u̶r̶i̶n̶e̶. w̶h̶i̶c̶h̶ i̶s̶ n̶o̶t̶ w̶h̶a̶t̶ A̶D̶H̶ d̶o̶e̶s̶.
Edit: I completely misread option B, and you’re right, technically it would make sense if Na left the duct into the blood stream for water to follow. But, that would mean that there would be increased levels of sodium in the blood, and it turns out that:
“The main sign and consequence of ADH is [hyponatremia], which is when you have low levels of sodium (salt) in your blood.” according to cleveland clinic.
therefore, practically, option B would be incorrect. I think…
Doesnt Aldosterone act on the collecting duct though controlling Sodium reabsorption, which would make B correct?
Had a quick read up on this! This is to do with the concentration of sodium in the blood going down as a result of more water being reabsorbed, wouldn’t disprove B i dont think!
Ok I’ll into this again, sorry
well thank you so much for a detailed answer. but it is still confusing how it wouldn’t work as B. cause if the solute concentration is high it would come water to go in. but one thing, the high sodium amount could make the cells there blast as well. so not the water going from the duct but the cells already in the duct’s water. idk that’s what i came up with
it’s a tricky question. have you tried chat gpt?
i havent because it includes a photo so i couldn’t copy paste
ADH affects aquaporin specifically.