What is a major way that hydration levels are measured by the body?

• A. Potassium content of blood measured by the hypothalamus.
• B. Potassium content of blood measured by the kidneys.
• C. Sodium content of blood measured by the hypothalamus.
• D. Sodium content of blood measured by the kidneys.

Answer: (C)

Verified step by step guidance

1. Understand the role of hydration in the body: Hydration levels are regulated by the balance of electrolytes, such as sodium and potassium, in the blood. These electrolytes help maintain fluid balance and are monitored by specific organs.
2. Recognize the role of sodium: Sodium is a key electrolyte that influences hydration. Its concentration in the blood is closely monitored because it affects the movement of water between cells and the bloodstream.
3. Identify the hypothalamus's function: The hypothalamus is a part of the brain that plays a critical role in maintaining homeostasis, including monitoring hydration levels. It detects changes in blood sodium concentration and triggers thirst or hormonal responses to restore balance.
4. Differentiate between sodium and potassium: While both are important electrolytes, sodium is the primary one used by the hypothalamus to assess hydration levels. Potassium is more involved in cellular functions and is not the main indicator for hydration monitoring.
5. Conclude that the correct answer is 'Sodium content of blood measured by the hypothalamus,' as this reflects the physiological mechanism by which the body assesses hydration levels.