The main function of the hypothalamus is homeostasis , or maintaining the body's status quo. Factors such as blood pressure, body temperature, fluid and electrolyte balance, and body weight are held to a precise value called the set-point. Although this set-point can migrate over time, from day to day it is remarkably fixed. To achieve this task, the hypothalamus must receive inputs about the state of the body, and must be able to initiate compensatory changes if anything drifts out of whack.
Information includes blood pressure and gut distension.
Among them is information about skin temperature, which is relayed to the hypothalamus. This allows them to monitor substances in the blood that would normally be shielded from neural tissue. Examples are the OVLT , which is sensitive to changes in osmolarity, and the area postrema , which is sensitive to toxins in the blood and can induce vomiting. Both of these project to the hypothalamus. The hypothalamus also has some intrinsic receptors, including thermoreceptors and osmoreceptors to monitor temperature and ionic balance, respectively.