Which of the following best describes the negative feedback loop involving the hypothalamus, pituitary gland, adrenal glands, and cortisol?

• A. The hypothalamus releases CRH, stimulating the pituitary to release ACTH, which prompts the adrenal glands to secrete cortisol; increased cortisol then inhibits CRH and ACTH release.
• B. Cortisol stimulates the hypothalamus to release ACTH, which then causes the adrenal glands to secrete CRH.
• C. The adrenal glands release ACTH, which stimulates the pituitary to secrete cortisol, and cortisol increases CRH release from the hypothalamus.
• D. The pituitary gland releases cortisol directly, which stimulates the hypothalamus to produce more CRH.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of a negative feedback loop. Negative feedback loops are mechanisms in the body that help maintain homeostasis by reducing the output or activity of a system when its effects become excessive.
2. Step 2: Identify the key players in this feedback loop: the hypothalamus, pituitary gland, adrenal glands, and cortisol. Each of these components plays a specific role in regulating hormone levels.
3. Step 3: Learn the sequence of hormone release in this system. The hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH then prompts the adrenal glands to secrete cortisol.
4. Step 4: Understand the inhibitory effect of cortisol. Elevated cortisol levels act on both the hypothalamus and pituitary gland to reduce the release of CRH and ACTH, respectively, completing the negative feedback loop.
5. Step 5: Compare the descriptions provided in the problem to the physiological process described above. The correct description should match the sequence of hormone release and the inhibitory role of cortisol in the negative feedback loop.