When a person is thirsty, a drink of water can be very satisfying, but after the thirst has been quenched, drinking more can be unpleasant. New research reveals the root of these experiences in the brain.
Researchers scanned the brains of people as they drank water. Brain areas involved in emotional decision-making lit up in the scanner when people drank in response to feeling thirsty, whereas regions involved in controlling movement kicked in when people forced themselves to keep drinking after quenching their thirst.
These brain circuits probably evolved to prevent people from drinking too much water, resulting in dangerously low sodium levels, the researchers reported today (March 24) in the journal Proceedings of the National Academy of Sciences. [7 Foods You Can Overdose On]
The instinct for thirst in humans and other animals likely evolved when vertebrates (animals with backbones) colonized land during the Ordovician period, about 400 million years ago. Thirst ensures that creatures maintain a balance of hydration and nutrients, such as sodium, that are vital to the healthy functioning of cells.
But what's going on inside the human brain when a person drinks to satisfy a thirst?
For the rest of the story: http://www.livescience.com/44319-feeling-thirsty-how-drinking-water-satisfies-brain.html