Experimental transection of the brainstem in an animal at the level of the mid-pons, combined with section of both vagus nerves, produces sustained inspiratory cramping with occasional expirations. Which structure's removal explains this apneusis?

• A Dorsal respiratory group neurons
• B Apneustic center in the lower pons
• C Pre-Botzinger complex in the medulla
• D Pneumotaxic center in the upper pons ✓

Explanation

The pneumotaxic center in the upper pons inhibits inspiration and limits inspiratory time, thereby regulating tidal volume and respiratory rate. When it is removed along with vagal feedback, the unopposed apneustic activity of the lower pons drives prolonged inspiratory gasps, producing apneusis. The pre-Botzinger complex generates the basic rhythm itself, so its loss would abolish breathing rather than prolong inspiration.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.