Herring Breuer reflex is an increase in
**Core Concept**
The Herring-Breuer inflation reflex is a physiological response that occurs in the lungs to prevent overinflation. It is mediated by the vagus nerve and involves the activation of stretch receptors in the alveoli and bronchi.
**Why the Correct Answer is Right**
When the lungs are inflated, the stretch receptors in the alveoli and bronchi are activated, sending signals to the brainstem via the vagus nerve. This activation leads to an increase in the inspiratory threshold pressure, making it more difficult to inspire air into the lungs. This reflex is an important mechanism for preventing overinflation of the lungs, which can lead to barotrauma and other complications. The Herring-Breuer inflation reflex is a protective mechanism that helps to maintain lung homeostasis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Herring-Breuer inflation reflex is not primarily an increase in respiratory rate. While respiratory rate may decrease as a result of the reflex, this is not the primary mechanism.
**Option B:** This option is incorrect because the Herring-Breuer inflation reflex is not an increase in airway resistance. In fact, the reflex can lead to a decrease in airway resistance as the airways dilate in response to the increased stretch.
**Option C:** This option is incorrect because the Herring-Breuer inflation reflex is not an increase in lung volume. The reflex actually helps to prevent overinflation of the lungs by making it more difficult to inspire air into the lungs.
**Clinical Pearl / High-Yield Fact**
The Herring-Breuer inflation reflex is an important mechanism for preventing overinflation of the lungs, particularly in patients with chronic obstructive pulmonary disease (COPD). In these patients, the reflex may be impaired, leading to increased susceptibility to barotrauma and other complications.
**Correct Answer:** A. Increase in inspiratory threshold pressure