Which statement(s) describe aspects of the Hering-Breuer reflex?

Question

1. It affects the rate and depth of breathing during exercise.
2. It is only activated at large tidal volumes in normal adults.
3. Its impulses travel via the vagus nerve to the dorsal respiratory groups (DRGs).
4. Its receptors are located in the large and small airways.
a. 1 only
b. 1 and 2 only
c. 2, 3, and 4 only
d. 1, 2, 3, and 4

Answer 1

ANS: D
The Hering-Breuer inflation reflex, described by H. E. Hering and Josef Breuer in 1868, is gen-erated by stretch receptors located in the smooth muscle of both large and small airways. When lung inflation stretches these receptors, they send inhibitory impulses through the vagus nerve to the DRG neurons, stopping further inspiration. In this way, the Hering-Breuer reflex has an ef-fect similar to that of the pneumotaxic center. In adults, the Hering-Breuer reflex is activated only at large tidal volumes (800 to 1000 ml or more) and, apparently, it is not an important con-trol mechanism in quiet breathing. However, this reflex is important in regulating respiratory rate and depth during moderate to strenuous exercise.