Systemic infusion of hypertonic saline stimulates vasopressin secretion within minutes. Which structure senses this osmotic stimulus despite being outside the conventional blood-brain barrier?

• A Supraoptic nucleus neurons
• B Median eminence tanycytes
• C Area postrema
• D Organum vasculosum of the lamina terminalis ✓

Explanation

The organum vasculosum of the lamina terminalis (OVLT) is a circumventricular organ that lies outside the blood-brain barrier, allowing its osmoreceptive neurons to detect changes in plasma osmolality directly. It projects to supraoptic and paraventricular nuclei to drive ADH release and thirst. The area postrema senses circulating toxins rather than tonicity, and the median eminence is primarily neuroendocrine.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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