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Hering-Breuer Reflex


Two reflexes discovered by Hering and Breuer in 1868 appear to help regulate the work of breathing on a breath-to-breath basis. The Hering-Breuer Inflation reflex (also called inhibito-inspiratory reflex) is initiated by stretch receptors (sensors) located in the smooth muscles surrounding both large and small airways. With lung inflation, these stretch receptors are stimulated and send neural signals via vagal afferents that appear to be inhibitory to the pontine apneustic center. Thus, they function to facilitate termination of inspiration, as previously noted in the neural transection studies. There is also a Hering-Breuer Deflation reflex (or excito-inspiratory reflex). This reflex is initiated either by decreased activity in the same airway stretch receptors involved in the inflation reflex or by stimulation of other proprioceptors that are activated by lung deflation. This information is also conveyed via vagal afferents to the brain stem respiratory centers to encourage inspiration. While Hering-Breuer reflexes are readily demonstrated in anesthetized animals, they are more difficult to demonstrate in humans, except at large tidal volumes. These reflexes are detectable in infants and are probably important in regulating the work of breathing.
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