Damage to the Phrenic Nerves Would

Question

Damage to the phrenic nerves would
A) increase respiratory rate.
B) increase the tidal volume.
C) force reliance on costal breathing.
D) result in greater pressure differences between the lungs and the outside air.
E) have little effect on ventilation.

Accepted Answer

The phrenic nerves innervate the diaphragm, which is the primary muscle of inspiration. Damage to these nerves would result in paralysis of the diaphragm on the affected side, forcing reliance on costal breathing (use of intercostal muscles). This would result in a decrease in tidal volume and potentially an increase in respiratory rate to compensate for the decreased air movement. However, options A, B, D, and E are all incorrect as they suggest an increase or no change in ventilation, which would not be the case with phrenic nerve damage.