The cardiopulmonary baroreceptors (low-pressure receptors) in the walls of the atria and pulmonary vessels respond to volume overload. When activated by increased atrial pressure, they produce reflex changes via the Henry-Gauer reflex. What are these changes?

• A Increased ADH secretion, increased renal sympathetic tone, and increased thirst to retain volume
• B Stimulation of ANP release from the atria along with paradoxical vasoconstriction to maintain cardiac output
• C Inhibition of ADH secretion, decreased renal sympathetic tone leading to natriuresis/diuresis, and inhibition of renin release ✓
• D Activation of medullary vasomotor center causing bradycardia and increased peripheral resistance

Explanation

The Henry-Gauer reflex (Gauer-Henry reflex) is a volume regulatory reflex: increased atrial stretch (detected by atrial mechanoreceptors with myelinated and unmyelinated vagal afferents) signals volume excess to the hypothalamus and brain stem. The reflex response includes: (1) inhibition of ADH (AVP) release from the posterior pituitary, reducing water retention; (2) reduced renal sympathetic nerve activity, increasing renal blood flow and GFR with subsequent natriuresis; (3) suppression of renin secretion, reducing angiotensin II and aldosterone. Separately, atrial stretch also releases ANP, which reinforces these effects. This reflex ensures blood volume homeostasis by unloading the volume when atrial filling pressure rises.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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