when blood volume and pressure is low which part of the brain triggers the thirst response
Thirst There are receptors and other systems in the body that detect a decreased volume or an increased osmolite concentration. They signal to the central nervous system, where central processing succeeds. Some sources,[1] therefore, distinguish "extracellular thirst" from "intracellular thirst", where extracellular thirst is thirst generated by decreased volume and intracellular thirst is thirst generated by increased osmolite concentration. Nevertheless, the craving itself is something generated from central processing in the brain, no matter how it is detected.