Which reflex can cause a decrease in blood pressure in response to norepinephrine via baroreceptors?

Which reflex can cause a decrease in blood pressure in response to norepinephrine via baroreceptors?

• A. Baroreceptor Reflex
• B. Bezold-Jarisch Reflex
• C. Cushing Reflex
• D. Vasovagal Reflex

Answer: (D)

Autonomic reflex control of blood pressure relies on baroreceptors in the carotid sinus and aortic arch sensing arterial stretch and signaling the brainstem to adjust heart rate, contractility, and vascular tone. When norepinephrine raises blood pressure through sympathetic activation, baroreceptors fire more, and the brainstem responds by increasing parasympathetic (vagal) output and reducing sympathetic outflow. In some situations this response becomes exaggerated in a vasovagal manner: a surge of vagal activity together with withdrawal of sympathetic tone leads to bradycardia and widespread vasodilation, causing a marked drop in blood pressure. This reflex is the classic scenario of a reflex-mediated hypotension and bradycardia, often seen in fainting spells triggered by stress or pain. The baroreceptor reflex itself is the normal mechanism that stabilizes blood pressure, so while it can contribute to lowering blood pressure after a norepinephrine-induced rise, the vasovagal reflex describes the more pronounced, episodic hypotension with vagal dominance. The other reflexes involve different triggers and pathways (ventricular mechanoreceptor–driven responses, intracranial pressure–related changes, and contemplations around the baroreceptor set point) and do not fit the typical pattern of a sudden, vagally mediated fall in blood pressure in response to baroreceptor signaling.

Autonomic reflex control of blood pressure relies on baroreceptors in the carotid sinus and aortic arch sensing arterial stretch and signaling the brainstem to adjust heart rate, contractility, and vascular tone. When norepinephrine raises blood pressure through sympathetic activation, baroreceptors fire more, and the brainstem responds by increasing parasympathetic (vagal) output and reducing sympathetic outflow. In some situations this response becomes exaggerated in a vasovagal manner: a surge of vagal activity together with withdrawal of sympathetic tone leads to bradycardia and widespread vasodilation, causing a marked drop in blood pressure. This reflex is the classic scenario of a reflex-mediated hypotension and bradycardia, often seen in fainting spells triggered by stress or pain.

The baroreceptor reflex itself is the normal mechanism that stabilizes blood pressure, so while it can contribute to lowering blood pressure after a norepinephrine-induced rise, the vasovagal reflex describes the more pronounced, episodic hypotension with vagal dominance. The other reflexes involve different triggers and pathways (ventricular mechanoreceptor–driven responses, intracranial pressure–related changes, and contemplations around the baroreceptor set point) and do not fit the typical pattern of a sudden, vagally mediated fall in blood pressure in response to baroreceptor signaling.