Baroreceptory

Baroreceptory, or baroreceptors, are mechanosensitive sensory receptors in the arterial system that detect changes in blood pressure by sensing stretch of the vessel wall. The principal sites are the carotid sinus at the bifurcation of the common carotid artery and the walls of the aortic arch. The carotid sinus receptors are innervated by the glossopharyngeal nerve (cranial nerve IX), while the aortic arch receptors are innervated by the vagus nerve (cranial nerve X). Central projections run to the nucleus tractus solitarius in the medulla oblongata, where afferent signals are integrated with other autonomic inputs.

When arterial pressure rises, baroreceptor firing increases due to greater stretch. This information is transmitted to the brainstem, which enhances parasympathetic (vagal) outflow to the heart and reduces sympathetic drive to the heart and blood vessels. The result is a lower heart rate, reduced contractility, and vasodilation, helping to return blood pressure toward normal. A decrease in blood pressure lowers baroreceptor firing, triggering the opposite autonomic responses to raise pressure. Baroreceptors thus provide rapid, beat-to-beat feedback that contributes to short-term arterial pressure regulation.

Over longer periods, baroreceptors can reset their baseline sensitivity in response to sustained blood pressure changes, such as chronic hypertension, which diminishes their role in long-term BP control. Consequently, long-term blood pressure is largely governed by other mechanisms, including renal and hormonal systems.

Clinically, baroreceptor function can be assessed via tests of baroreflex sensitivity; dysfunction may occur in autonomic disorders, aging, or diabetes. Carotid sinus massage can transiently stimulate baroreceptors and provoke bradycardia or hypotension in susceptible individuals.