Baroreceptors detect changes in which parameter essential for homeostasis?

• A. Oxygen partial pressure
• B. Blood glucose
• C. Body temperature
• D. Blood pressure

Answer: (D)

Baroreceptors are stretch-sensitive sensors in the walls of major arteries, especially the carotid sinuses and the aortic arch. They continuously monitor arterial pressure by detecting how much the vessel walls are stretched. When blood pressure rises, increased stretch raises their firing rate, signaling the brainstem to reduce sympathetic output and increase parasympathetic activity, which lowers heart rate and dilates vessels to bring pressure down. When pressure falls, their firing decreases, prompting the opposite response—faster heart rate, stronger contractions, and vasoconstriction—to raise blood pressure back toward normal. This rapid reflex helps maintain stable blood flow to organs, a key part of homeostasis.

Oxygen partial pressure is mainly sensed by chemoreceptors that regulate breathing rather than arterial pressure. Blood glucose levels are monitored by metabolic and endocrine systems rather than by arterial stretch sensors. Body temperature is controlled by the hypothalamus and thermoreceptors to balance heat gain and loss, not by baroreceptors.