components of smoke and smog, and to inhaled particulates. The rapidly adapting receptors in the lungs are stimulated most directly by an increase in the amount of fluid in the pulmonary interstitial tissue. Since the same chemicals that stimulate the unmyelinated C fibers can cause increased pulmonary interstitial fluid (due to extravasation from pulmonary capillaries—see chapter 14), a person may also cough after eating hot peppers.
The Hering-Breuer reflex is stimulated by pulmonary stretch receptors. The activation of these receptors during inspiration inhibits the respiratory control centers, making further inspiration increasingly difficult. This helps to prevent undue distension of the lungs and may contribute to the smoothness of the ventilation cycles. A similar inhibitory reflex may occur during expiration. The Hering-Breuer reflex appears to be important in maintaining normal ventilation in the newborn. Pulmonary stretch receptors in adults, however, are probably not active at normal resting tidal volumes (500 ml per breath) but may contribute to respiratory control at high tidal volumes, as during exercise.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.