How Thirst and satiety influence water intake?
Thirst and satiety influence water intake, apparently in response to changes sensed by the mouth, hypothalamus and nerves. When the blood is too concentrated (having lost water, but not the dissolved substances within it), the mouth becomes dry, and the person responds by drinking .When the hypothalamus detects that the blood is too concentrated, it also initiates the drinking behaviour. Besides stimulating the thirst sensation, the hypothalamus stimulates the pituitary gland to release ADH. This hormone increases the reabsorption of water. Thirst drives a person to seek water, but it often lags behind the body's needs. A water deficiency that develops slowly can switch on the drinking behaviour in time to prevent dehydration, but a deficiency that develops quickly may not. Also, thirst itself may not always remedy a water deficiency; a person must notice the thirst signal, pay attention, and take time to get a drink. The long distance runner, the gardener in hot weather, the child busy playing, and the elderly person whose thirst sensation may be blunted can experience serious dehydration if they fail to drink promptly in response to their need for water.