Your Sense of Thirst is Complicated
Let's say you just finished a long walk on a warm afternoon, then stop to drink a tall glass of water and take a long drink. Usually, the dryness in your mouth eases, your throat reflexes and you feel satisfied. But that water won't hit your bloodstream for at least another half hour, so why does your brain stop telling you to drink?
The answer to that question has to do with how your body manages on of its most essential resources and why so many of us walk around mildly dehydrated with ever feeling it.
Buried in your brain are two small regions that keep watch on the balance of water and salt in your blood. When that ratio changes a little, it triggers that sensation that we call thirst. According to a report from Quanta Magazine discussing the neuroscience of thirst, it only takes a 1% change in your blood's water content to trip the thirst alarm.