ADH is released in response to dehydration. They act on the kidneys for water retention. Simultaneously, the hypothalamus signals a thirst response. Intake and movement of water from urine to blood dilutes plasma osmolality which returns blood to its normal state. This is most sensitive to an increase in osmolality however, it is activated by a large loss in the plasma volume. The ADH acts on the vasculature to cause the narrowing of the blood vessels. The net actions of this feedback loop cause an increase in blood pressure.