What is the correct sequence of events in the HPA axis during the stress response?

• A. Hypothalamus releases corticotropin-releasing hormone, prompting the pituitary to release adrenocorticotropic hormone, which stimulates cortisol from the adrenal glands.
• B. Pituitary releases adrenocorticotropic hormone, which stimulates cortisol release, and the hypothalamus releases corticotropin-releasing hormone afterwards.
• C. Hypothalamus releases corticotropin-releasing hormone, prompting pituitary ACTH release, which stimulates cortisol from the adrenal glands.
• D. Adrenal glands release cortisol first, signaling the hypothalamus to release corticotropin-releasing hormone and pituitary to release adrenocorticotropic hormone.

Answer: (C)

The key idea is the hormonal cascade that starts in the hypothalamus and moves to the pituitary and then to the adrenal glands. In response to stress, the hypothalamus releases corticotropin-releasing hormone, which signals the pituitary to release adrenocorticotropic hormone. ACTH then travels to the adrenal cortex and stimulates the production of cortisol. This sequence—CRH from the hypothalamus, ACTH from the pituitary, cortisol from the adrenal cortex—captures how the HPA axis mobilizes energy and manages the stress response. The other options misorder those steps or imply cortisol is released before ACTH, which contradicts the cascade. There’s also a feedback loop: once cortisol rises, it helps dampen CRH and ACTH production to regulate the response.