Exam 13: Homeostasis: Active Regulation of the Internal Environment

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Thirst is a physiological sensation that drives behavior to seek out and consume water. When the body becomes dehydrated, the kidneys release the enzyme renin, which initiates the renin-angiotensin system. This system ultimately leads to the production of angiotensin II, a hormone that plays a key role in regulating blood pressure and fluid balance. Angiotensin II also acts on the circumventricular organs, specialized brain regions that lack a blood-brain barrier and are sensitive to changes in the body's internal environment. These organs help to integrate signals related to thirst and fluid balance, ultimately influencing behavior to encourage water intake. Therefore, the interaction between thirst, renin, angiotensin II, and the circumventricular organs highlights the complex physiological and behavioral mechanisms involved in maintaining proper hydration levels in the body.