The baroreceptor reflex is activated by increased arterial pressure sensed in the carotid sinus and aortic arch. The immediate cardiovascular response is:

• A Increased sympathetic tone causing tachycardia and vasoconstriction
• B Activation of the renin-angiotensin system
• C Increased parasympathetic tone causing bradycardia and decreased sympathetic vasoconstriction ✓
• D ADH release causing water retention

Explanation

Baroreceptors are stretch-sensitive afferents in the carotid sinus (CN IX) and aortic arch (CN X) that increase firing when wall tension rises with elevated blood pressure. These signals reach the nucleus tractus solitarius in the medulla, which reflexively increases parasympathetic (vagal) outflow to the heart (causing bradycardia and reduced contractility) and withdraws sympathetic tone to the vasculature (causing vasodilation). This buffer reflex opposes acute pressure rises but does not reset long-term blood pressure.

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

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