Question

How do you tell the difference between the phrenic and vagus nerves?

a) By their function in the diaphragm
b) By their origin from the brainstem
c) By their sensory innervation
d) By their pathway through the thorax

Answer 1

The phrenic and vagus nerves differ in their pathways through the thorax; the phrenic nerve innervates the diaphragm, while the vagus nerve extends from the brainstem to manage autonomic functions in the thorax and abdomen.

Step-by-step explanation:

You can differentiate between the phrenic and vagus nerves by their pathway through the thorax. The phrenic nerve is a systemic nerve from the cervical plexus that innervates the diaphragm and is responsible for the muscle contractions that drive ventilation. Its motor fibers connect to the spinal cord at cervical levels 3 to 5. In contrast, the vagus nerve (cranial nerve X) is one of the twelve cranial nerves, which has autonomic functions within the thoracic and superior abdominal cavities. It plays a significant role in controlling the heart, lungs, and digestive tract. The vagus nerve arises from the brainstem rather than the spinal cord and has a broad distribution reaching organs in the thorax and abdomen.