Conversation so far:
where do the phrenic and vagus nerves originate
The courses of the phrenic and the vagus nerves are similar: they both start in the neck, run downward in the mediastinum, and pass through the diaphragm.
What is the function of the phrenic nerve
The phrenic nerve is the motor and sensory nerve of the diaphragm.

Question: What is the function of the second nerve
Self-contained rewrite: What is the function of the vagus nerve