Neural Sensing of Organ Volume

Many internal organs change volume periodically. For example, the stomach accommodates ingested food and drink, the bladder stores urine, the heart fills with blood, and the lungs expand with every breath. Specialized peripheral sensory neurons function as mechanoreceptors that detect tissue stretch to infer changes in organ volume and then relay this information to the brain. Central neural circuits process this information and evoke perceptions (satiety, nausea), control physiology (breathing, heart rate), and impact behavior (feeding, micturition). Yet, basic questions remain about how neurons sense organ distension and whether common sensory motifs are involved across organs. Here, we review candidate mechanosensory receptors, cell types, and neural circuits, focusing on the stomach, bladder, and airways. Understanding mechanisms of organ stretch sensation may provide new ways to treat autonomic dysfunction.