Which receptors respond to the stretching of arterial walls and cause a decrease in heart rate when blood pressure rises?

• A. Chemoreceptors
• B. Proprioceptors
• C. Adrenaline
• D. Baroreceptors

Answer: (D)

Baroreceptors are stretch-sensitive receptors in the walls of major arteries (like the carotid sinus and aortic arch). They detect how stretched the vessel walls are, which reflects the blood pressure. When blood pressure rises, these receptors fire more rapidly and send signals to the brainstem. The brain then increases parasympathetic (vagal) output to the heart and reduces sympathetic drive, lowering the heart rate. This reflex action helps bring blood pressure back toward normal.

Chemoreceptors respond to chemical changes (O2, CO2, pH) rather than stretch; proprioceptors sense limb position and movement; adrenaline is a hormone, not a receptor.