Hypothalamus monitors blood composition

Steps:

• Recall brain structures and their primary functions in homeostasis.
• Identify that blood concentration changes involve osmolality and hormone levels.
• Match the function of detecting these changes to the hypothalamus.
• Eliminate options based on unrelated roles.

Why B is correct:

• The hypothalamus acts as a sensor for blood osmolality and electrolyte concentrations, regulating thirst and hormone release via osmoreceptors.

Why the others are wrong:

• A. Cerebellum coordinates movement and balance, not blood monitoring.
• C. Medulla controls vital functions like heart rate and breathing, unrelated to blood concentration.
• D. Pituitary gland secretes hormones in response to signals but does not directly register blood changes.

Final answer: B