baroreseptorrefleksen

Baroreceptor reflex, known in Swedish as baroreseptorrefleksen, is a rapid, automatic mechanism that helps maintain stable blood pressure. The reflex is mediated by specialized stretch‑sensing nerve endings, called baroreceptors, located primarily in the carotid sinus and aortic arch. These receptors are sensitive to changes in arterial wall tension, which correlate with blood pressure.

When arterial blood pressure rises, the increased stretch of the baroreceptor membranes activates afferent signals that travel via the glossopharyngeal and vagus nerves to the nucleus tractus solitarius (NTS) in the medulla oblongata. The NTS integrates the input and sends efferent signals through the autonomic nervous system. In response to a high blood pressure stimulus, the sympathetic nervous system is inhibited while the parasympathetic output is enhanced. The resulting decrease in heart rate, cardiac contractility, and peripheral vascular resistance helps lower blood pressure toward normal levels.

Conversely, a drop in arterial pressure reduces baroreceptor firing. This leads to increased sympathetic tone and decreased parasympathetic activity, producing tachycardia, increased cardiac output, and vasoconstriction, thereby restoring blood pressure. The baroreceptor reflex thus provides a continuous, short‑term corrective mechanism that buffers rapid fluctuations in systemic blood pressure.

The reflex is finely tuned and can adapt over time; chronic hypertension, for instance, can shift the pressure set point such that baroreceptor firing patterns normalize at a higher pressure. Disorders affecting baroreceptor function, such as autonomic failure or baroreflex failure, can result in labile or extreme blood pressure variations. Clinical evaluation of baroreceptor sensitivity is sometimes performed using tilt‑table testing, pharmacologic agents, or physiologic maneuvers (e.g., Valsalva). Understanding the baroreceptor reflex is essential for comprehending cardiovascular physiology and for diagnosing and treating disorders of blood pressure regulation.