Which statement concerning vasopressin secretion is NOT true?

Which statement concerning vasopressin secretion is NOT true?

• A. All of these
• B. Vasopressin secretion is closely tied to plasma osmolality.
• C. Changes in blood volume also alter vasopressin secretion.
• D. A reduction in effective blood volume overrides the effects of plasma osmolality in regulating vasopressin secretion.

Answer: (D)

Vasopressin release is driven mainly by plasma osmolality. When osmolality rises, osmoreceptors in the hypothalamus detect the higher solute concentration and trigger vasopressin secretion, promoting water reabsorption in the kidneys to concentrate the urine and restore plasma osmolality. Blood-volume changes also influence vasopressin, because baroreceptors respond to decreases in effective circulating volume by nudging vasopressin release to conserve water and help maintain pressure. However, in the normal range, this volume-related signal is a modulatory input rather than the dominant driver; osmolality remains the primary cue. The statement claiming that a reduction in effective blood volume overrides the effects of plasma osmolality is not correct because the osmotic signal generally governs vasopressin release more potently, with volume status contributing additively but not completely superseding osmotic control.

Vasopressin release is driven mainly by plasma osmolality. When osmolality rises, osmoreceptors in the hypothalamus detect the higher solute concentration and trigger vasopressin secretion, promoting water reabsorption in the kidneys to concentrate the urine and restore plasma osmolality.

Blood-volume changes also influence vasopressin, because baroreceptors respond to decreases in effective circulating volume by nudging vasopressin release to conserve water and help maintain pressure. However, in the normal range, this volume-related signal is a modulatory input rather than the dominant driver; osmolality remains the primary cue.

The statement claiming that a reduction in effective blood volume overrides the effects of plasma osmolality is not correct because the osmotic signal generally governs vasopressin release more potently, with volume status contributing additively but not completely superseding osmotic control.