**Core Concept**
Baroreceptors are specialized mechanoreceptors found in the arterial walls, particularly in the carotid sinus and aortic arch. They play a crucial role in maintaining blood pressure homeostasis by detecting changes in arterial stretch and transmitting signals to the central nervous system.

**Why the Correct Answer is Right**
When baroreceptors are stimulated, they send signals to the nucleus tractus solitarii in the medulla oblongata. This activation triggers a reflex response that results in a decrease in sympathetic outflow and an increase in parasympathetic outflow. The decrease in sympathetic activity causes vasodilation, leading to a decrease in peripheral resistance and consequently a decrease in blood pressure. Additionally, the increase in parasympathetic activity stimulates the vagus nerve, which also contributes to the decrease in heart rate, further contributing to the reduction in blood pressure.

**Why Each Wrong Option is Incorrect**
**Option A:** Inhibition of parasympathetic activity would actually increase heart rate and blood pressure, as the parasympathetic nervous system has a calming effect on the heart and promotes vasodilation.

**Option B:** Excitation of sympathetic activity would increase heart rate and blood pressure, as the sympathetic nervous system stimulates the heart and promotes vasoconstriction.

**Option C:** Increase in heart rate is actually a response to decreased baroreceptor stimulation, not increased stimulation. When baroreceptors are stimulated, they decrease heart rate to lower blood pressure.

**Clinical Pearl / High-Yield Fact**
A key clinical correlation to remember is that baroreceptor reflex is a critical mechanism for regulating blood pressure in response to changes in blood volume. This reflex is often impaired in conditions such as hypertension, where the baroreceptors become desensitized and fail to effectively regulate blood pressure.

**✓ Correct Answer: D. Decrease in blood pressure**