A decrease in arterial pressure is quickly identified by the ___, which initiates a negative feedback loop.

• A. Chemoreceptors
• B. Baroreceptors
• C. Osmoreceptors
• D. Pacemaker cells

Answer: (B)

Baroreceptors are stretch-sensitive sensors in the carotid sinus and aortic arch that continuously monitor arterial pressure. When pressure drops, the walls stretch less, so these receptors fire less. The brainstem detects this reduced input and triggers a corrective response: it increases sympathetic output and decreases parasympathetic activity, which raises heart rate, enhances contractility, and causes vasoconstriction. These actions raise arterial pressure back toward normal, completing a negative feedback loop. Chemoreceptors, osmoreceptors, and pacemaker cells have different primary roles, so they don’t provide the rapid pressure sensing that initiates this reflex.