Rockgo288
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Just want to ask is ADH the ultimate factor that controls water potential in blood?
Or does nephron and hormones both control it? Cause i don’t understand how nephron can maintain the water potential.
For ADH, i know when water potential is higher, less ADH is released. Vice Versa.
But how does the loop of henle do that? Isn’t ADH the final factor that controls the permeability of collecting duct? so it all depends on ADH?
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georgem93
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(Original post by Rockgo288)
Just want to ask is ADH the ultimate factor that controls water potential in blood?
Or does nephron and hormones both control it? Cause i don’t understand how nephron can maintain the water potential.
For ADH, i know when water potential is higher, less ADH is released. Vice Versa.
But how does the loop of henle do that? Isn’t ADH the final factor that controls the permeability of collecting duct? so it all depends on ADH?
Look more closely into what the role of the loop of henle is
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Rockgo288
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(Original post by georgem93)
Look more closely into what the role of the loop of henle is
So, in descending limb, water pass out of filtrate, leading to higher water potential in blood.
Then, at base of ascending limb, Na+ diffuse out so lowering water potential of blood.
At collecting duct, water pass out of filtrate so increasing water potential of blood. But this water loss can be controlled by ADH.

So, no matter what the water potential is, the loop of henle still does what it does to maintain water potential? but what react to changes in water potential is ADH? and ADH controls permeability of collecting duct so it kind of control the role of nephron in maintaining the water potential of blood???
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georgem93
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ADH is usually activated when the body doesn’t have enough water so that more gets reabsorbed.
It may be slightly out of the spec but look into why the loop of henle extends from the cortex into the medulla.
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straightIrishguy
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(Original post by Rockgo288)
But this water loss can be controlled by ADH.
Yes but not directly - ADH increases permeability of a aquaporins, which then allows H2O in urine to be reabsorbed - as the interstitial fluid surrounding the collecting ducts and DCT is very salty and therefore has a very negative solute and H2O potential, the water from collecting ducts moves back in- it's salty because the loop de henle pumps ions out into the interstitial fluid
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annanas45
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ADH controls the permeability of the descending limb and collecting duct by controlling the number of aquaporins in the membrane. So yes essentially it does depend on ADH, however water can still diffuse through the cells into the medulla and blood as it is a small molecule. if the body happens to be abnormally hydrated and absolutely no aquaporins were in the membranes water would still diffuse into the blood
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Rockgo288
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Umm... so after all, osmoregulation is carried out by nephron and hormones. But if nephron already does this job, why is ADH needed? Is it because as georgem93 said “ADH is usually activated when the body doesn’t have enough water”? That means ADH helps fine-tuning the water potential of blood?
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annanas45
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(Original post by Rockgo288)
Umm... so after all, osmoregulation is carried out by nephron and hormones. But if nephron already does this job, why is ADH needed? Is it because as georgem93 said “ADH is usually activated when the body doesn’t have enough water”? That means ADH helps fine-tuning the water potential of blood?
It doesn't happen fast enough without aquaporins
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