What reflex is associated with the sensory stimulation of the pulmonary stretch receptors that ...

(Answer to Q. 1)  ANS: B
If the Hering-Breuer reflex is blocked by cooling the vagus nerve, lung hyperinflation causes a further increase in inspiratory effort, the opposite of the Hering-Breuer reflex. The receptors for this reflex are called rapidly adapting receptors, because they stop firing promptly after a volume change occurs. Head's reflex may help maintain large tidal volumes during exercise and may be involved in periodic deep sighs during quiet breathing.

(Answer to Q. 2)  ANS: A
Rapidly adapting irritant receptors in the epithelium of the larger conducting airways have vagal sensory nerve fibers. Their stimulation, whether by inhaled irritants or by mechanical factors, causes reflex bronchoconstriction, coughing, sneezing, tachypnea, and narrowing of the glottis.

(Answer to Q. 3)  ANS: B
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 control mechanism in quiet breathing.

(Answer to Q. 4)  ANS: A
Some inspiratory VRG neurons send motor impulses through the vagus nerve to the laryngeal and pharyngeal muscles, abducting the vocal cords and increasing the diameter of the glottis. Other VRG inspiratory neurons transmit impulses to the diaphragm and external intercostal mus-cles.

(Answer to Q. 5)  ANS: D
The inhibitory neurons that switch off the inspiratory ramp signal are controlled by the pneumo-taxic center and pulmonary stretch receptors.

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