Illuminating peripheral vascular regulation: a classroom demonstration of the venoarteriolar reflex

The venoarteriolar reflex (VAR) is a peripheral vascular response that limits edema formation in dependent limbs. Despite its physiological relevance, it is rarely addressed in teaching laboratories. The author describes a simple, low-cost protocol that uses photoplethysmography (PPG) and basic postural changes to demonstrate the VAR in real time. In most classroom sessions, a reduction in PPG amplitude is observed during limb dependency and rapid recovery when the limb is returned to heart level. These observations provide a basis for discussing hydrostatic effect, Starling's forces, and myogenic mechanisms of vascular regulation. Because PPG reflects skin blood flow, the protocol also invites links to autonomic and endocrine physiology. Requiring minimal equipment and preparation, this demonstration offers an accessible and engaging tool for physiology education. This accessible and engaging protocol helps students integrate theoretical and experimental learning in vascular physiology.NEW & NOTEWORTHY This article presents a simple classroom demonstration of the venoarteriolar reflex (VAR) using photoplethysmography and limb positioning. This low-cost protocol allows students to visualize vascular regulation in real time and stimulates discussion of hydrostatic effect, myogenic activity, and edema prevention. Accessible and engaging, it offers instructors an easy way to connect theoretical principles with direct experimental observation.