Trunk · Nerve
Phrenic Nerve
The phrenic nerve controls the diaphragm — the main breathing muscle. It arises in the neck and, remarkably, keeps you breathing automatically day and night.
What it is
The phrenic nerve is a nerve arising from the neck (mainly the fourth cervical nerve) that travels down through the chest to the diaphragm.
Where it runs
From the neck, down through the chest alongside the heart, to the diaphragm.
What it does
Drives the diaphragm to contract, powering breathing; also carries some sensation from the chest lining.
When things go wrong
Common problems affecting the phrenic nerve
- Phrenic nerve injury causing a weak or paralysed diaphragm and breathlessness
- Hiccups (linked to diaphragm/phrenic activity)
Education and reference only. This explains the anatomy in plain terms and is not a diagnosis. New weakness or numbness, facial drooping, or loss of bladder or bowel control can be an emergency — call 999.
Did you know?
An interesting fact
A medical saying — "C3, 4, 5 keep the diaphragm alive" — reminds students that the phrenic nerve comes from these neck nerves, which is why high spinal injuries can stop breathing.
Answers
Phrenic Nerve: frequently asked questions
What does the phrenic nerve do?
It controls the diaphragm, the main breathing muscle, so it is essential for breathing.
Sources
Where this is drawn from
- NHS — Nervous system
- Gray's Anatomy for Students
- TeachMeAnatomy — nervous system
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