a decrease in volume and an increase in osmolarity of body fluids, when water loss is greater than water gain.
1. decrease flow of saliva leads to dry mouth and pharynx
.2. increased blood osmolarity leads to stimulation of osmorecetors in hypothalamus
3. decreased blood volume leads to decreased BP, which leads to increased renin release by juxtaglomerular cells of kidneys which leads to increased angiotensis II formation
all three of these lead to stimulation of thirst center in hypothalamus, increases thirst, increases water intake, and increases body water to normal level and relieves dehydration