The physiological regulation of plasma osmolality by osmotically active neurons (osmoreceptors) in the organum vasculosum of lamina terminalis (OVLT) of hypothalamus is described in the following statements:
A. In hyperosmolar state, the non-selective cationic channels in the osmoreceptor membrane become active causing hyperpolarization of receptor cells.
B. In hyperosmolar state, shrinkage of osmoreceptor cells occurs.
C. Activated osmoreceptors send action potentials to the supraoptic nucleus (SON) and paraventricular nucleus (PVN) to release arginine vasopressin (AVP).
D. In hyposmolar state, the stretching of osmoreceptor membrane causes inactivation of transient receptor vanilloid protein 4 (TRPV4) resulting in the activation of osmoreceptors.
Which one of the following options represents a combination of all correct statements?

Correct option is B

Correct Answer
(b) B and C
Explanation
In hyperosmolar states, water leaves osmoreceptor neurons causing cell shrinkage, making statement B correct. This activates osmoreceptors, which stimulate neurons in the SON and PVN to release arginine vasopressin (AVP), validating statement C. Statement A is incorrect because activation of non-selective cation channels leads to depolarization, not hyperpolarization. Statement D is also incorrect as TRPV4 inactivation in hyposmolar states reduces, rather than activates, osmoreceptor activity.
Information Booster
• OVLT lacks a blood–brain barrier, allowing direct sensing of plasma osmolality
• Hyperosmolarity increases AVP release to promote water reabsorption in kidneys
• Osmoreceptor cell shrinkage is a key trigger for neuronal activation
• SON and PVN are major hypothalamic nuclei involved in water balance
Additional Knowledge
Statement A is incorrect because opening of non-selective cation channels causes depolarization of osmoreceptors. Statement D is incorrect since hyposmolar stretching inactivates TRPV channels leading to reduced osmoreceptor firing, suppressing AVP release.