1/
Why is our thirst immediately quenched after the ingestion of water?
As we'll note, it takes ~10 minutes for serum osmolarity to change. And yet thirst drops far more rapidly.
Something must be bypassing the blood...
Why is our thirst immediately quenched after the ingestion of water?
As we'll note, it takes ~10 minutes for serum osmolarity to change. And yet thirst drops far more rapidly.
Something must be bypassing the blood...
2/
Though I suspect we all agree that thirst is quenched rapidly after a sip of water, some of you will demand data.
If you infusion 5% saline, thereby increasing osmolarity, thirst shoots up. But, as soon as drinking is allowed, thirst drops.
pubmed.ncbi.nlm.nih.gov/19523569/
Though I suspect we all agree that thirst is quenched rapidly after a sip of water, some of you will demand data.
If you infusion 5% saline, thereby increasing osmolarity, thirst shoots up. But, as soon as drinking is allowed, thirst drops.
pubmed.ncbi.nlm.nih.gov/19523569/
3/
Notice that in the experiment in tweet 2, the serum osmolarity had NOT dropped when thirst plummeted.
This is because it takes 10+ minutes for ingested water to be fully absorbed into the bloodstream, decreasing osmolarity.
link.springer.com/article/10.375…
Notice that in the experiment in tweet 2, the serum osmolarity had NOT dropped when thirst plummeted.
This is because it takes 10+ minutes for ingested water to be fully absorbed into the bloodstream, decreasing osmolarity.
link.springer.com/article/10.375…
4/
Amazing research has shown that the subfornical organ (the site that typically responds to SERUM osmolarity and/or angiotensin II levels) receives DIRECT inputs about what we place in our mouth during eating and drinking.
pubmed.ncbi.nlm.nih.gov/27487211/
Amazing research has shown that the subfornical organ (the site that typically responds to SERUM osmolarity and/or angiotensin II levels) receives DIRECT inputs about what we place in our mouth during eating and drinking.
pubmed.ncbi.nlm.nih.gov/27487211/
5/
Information about the composition of the food/liquid we eat allows the subfornical organ (SFO) to predict our future blood osmolarity.
It then changes our behavior accordingly.
pubmed.ncbi.nlm.nih.gov/27487211/
Information about the composition of the food/liquid we eat allows the subfornical organ (SFO) to predict our future blood osmolarity.
It then changes our behavior accordingly.
pubmed.ncbi.nlm.nih.gov/27487211/
6/
We eat something salty, the SFO receives this input and says: "Your osmolarity is about to go up. Be thirsty! Drink!"
We drink a glass of water, the SFO receives this input and says: "Your osmolarity is about to go down. You can slow down on the water. Be less thirsty!"
We eat something salty, the SFO receives this input and says: "Your osmolarity is about to go up. Be thirsty! Drink!"
We drink a glass of water, the SFO receives this input and says: "Your osmolarity is about to go down. You can slow down on the water. Be less thirsty!"
7/
All of this happens well before our serum osmolarity changes. Our brain anticipates changes and pre-emptively modulates our behavior.
SO COOL!
All of this happens well before our serum osmolarity changes. Our brain anticipates changes and pre-emptively modulates our behavior.
SO COOL!
If you infuse fluids and drop the serum osmolarity, thirst should drop quickly.
This is the opposite of what is seen in tweet 2 above.
This is the opposite of what is seen in tweet 2 above.
