Lung Inflation Signals Limit Inspiration The Hering Breuer Inflation Reflex

In addition to the central nervous system respiratory control mechanisms operating entirely within the brain stem, sensory nerve signals from the lungs also

Dorsal respiratory group (inspiration)

Vagus and glossopharyngeal

Fourth ventricle- ¡

Fourth ventricle- ¡

Dorsal respiratory group (inspiration)

Vagus and glossopharyngeal

Inhibits help control respiration. Most important, located in the muscular portions of the walls of the bronchi and bronchioles throughout the lungs are stretch receptors that transmit signals through the vagi into the dorsal respiratory group of neurons when the lungs become overstretched. These signals affect inspiration in much the same way as signals from the pneumotaxic center; that is, when the lungs become overly inflated, the stretch receptors activate an appropriate feedback response that "switches off" the inspiratory ramp and thus stops further inspiration. This is called the HeringBreuer inflation reflex. This reflex also increases the rate of respiration, as is true for signals from the pneu-motaxic center.

In human beings, the Hering-Breuer reflex probably is not activated until the tidal volume increases to more than three times normal (greater than about 1.5 liters per breath). Therefore, this reflex appears to be mainly a protective mechanism for preventing excess lung inflation rather than an important ingredient in normal control of ventilation.

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Essentials of Human Physiology

Essentials of Human Physiology

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