For example, hunger and thirst, these are disturbances in the internal environment that act as stimulus to a feedback system. When we lack intake of food and/or water we will experience hunger and/or thirst as a response to the stimulus. In hunger, when there is a lack of food intake the stomach and other organs in the system start to produce ghrelin which is the hormone responsible for signaling the brain of hunger. Therefore the ghrelin the blood will be detected by the brain signaling that there is a lack of food intake and thus, making us feel hungry. While thirst comes from the lack of fluids and/or the increase of the concentration of other substances as a result of that. A lot of hormones are involved in thirst, but Angiotensin II is the hormone one responsible for cascading events that lead to thirst.