What happens to thirst sensation following a hyperosmotic NaCl infusion?

• A. Thirst is suppressed
• B. Thirst is stimulated
• C. Thirst remains unchanged
• D. Thirst becomes intermittent

Answer: (B)

After a hyperosmotic NaCl infusion, the body's osmolarity increases due to the elevated concentration of solutes in the blood. This hyperosmotic condition stimulates osmoreceptors located in the hypothalamus, which play a critical role in regulating fluid balance and thirst. As the osmotic pressure rises, these osmoreceptors activate the thirst mechanism, leading to an increase in the sensation of thirst. This response is crucial because it prompts the individual to seek out fluids, helping to restore homeostasis by diluting the excess sodium and returning osmolarity to normal levels. The increase in thirst sensation is a vital compensatory mechanism that the body uses to manage changes in osmotic balance.