Final answer:
True, cells in the roof of the third ventricle of the brain, specifically in the hypothalamus, are intrinsic to regulating the thirst response and thereby affect the functioning of the thirst center.
Step-by-step explanation:
The statement that cells in the roof of the third ventricle of the brain affect the functioning of the thirst center is true.
The hypothalamus, which is part of the diencephalon and defines the walls of the third ventricle, plays a crucial role in regulating the thirst response.
Osmoreceptors located in the hypothalamus monitor the concentration of solutes, also known as osmolality, in the blood. When osmolality increases, indicating dehydration, the hypothalamus activates the thirst response.
The hypothalamus also signals the posterior pituitary gland to release antidiuretic hormone (ADH), which prompts the kidneys to conserve water and effectively dilutes blood plasma.
Thus, cells within the hypothalamus surrounding the third ventricle are intrinsic to the process of thirst regulation and water intake.