A chemotherapy agent causes severe vomiting even though it does not cross the intact blood-brain barrier elsewhere. The region of the brain that explains this observation lacks a functional blood-brain barrier and contains chemoreceptor neurons sampling the systemic circulation. This region is the:
- A Subfornical organ
- B Area postrema ✓
- C Organum vasculosum of the lamina terminalis
- D Median eminence
Correct answer: B. Area postrema
Explanation
The area postrema on the floor of the fourth ventricle is one of the circumventricular organs, where fenestrated capillaries allow circulating emetogens such as cytotoxic drugs and digitalis glycosides to reach neurons of the chemoreceptor trigger zone. The subfornical organ and OVLT sense angiotensin and osmolality for fluid balance, while the median eminence admits releasing hormones, so none explains drug-induced vomiting.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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