Lung volume (inspiration)
Vagal afferent pulse
Brainstem (NTS) off-switch
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Every breath you take is cut short by a feedback loop you never notice: as the lungs inflate, stretch receptors in the airway walls fire faster and faster, and once their signal — carried by the vagus nerve to the brainstem — crosses a threshold, inspiration is switched off and passive exhalation begins. This is the Hering-Breuer inflation reflex, first described in 1868 and still a working part of every mammal's respiratory control loop, especially prominent in newborns. This simulator models the lungs, vagus nerve and brainstem as a real relaxation oscillator: drag the inspiratory flow, off-switch threshold, vagal gain and expiratory time constant and watch the breathing rhythm reshape itself in 3D, from the slow deep breaths of a vagotomized animal (gain = 0) to the rapid shallow breaths typical of a hypersensitive reflex (gain ≈ 2×).