Osmoreceptors, which monitor blood solute concentration and trigger the thirst response, are located in the:

1. Thirst is triggered when blood becomes too concentrated (higher osmolality). 2. A dedicated thirst center senses this concentration change. 3. The osmoreceptors of this thirst center in the hypothalamus. 4. The posterior pituitary releases ADH in response to hypothalamic signals but does not itself sense osmolality. 5. So the hypothalamus is correct. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 26 "Fluid, Electrolyte, and Acid-Base Balance", p.1256 §Regulation of Water Intake_