The fight-or-flight chain
Sympathetic trunk · truncus sympathicus
A chain of nerve ganglia beside your spine that drives the fight-or-flight response.
What it does
The sympathetic trunks are two beaded chains of nerve clusters running beside the spine from the neck to the tailbone. Through them the sympathetic nervous system speeds the heart, widens the airways and pupils, diverts blood to muscles and slows digestion when you are stressed or exercising.
Surprising fact
The sympathetic system can also make the hairs on your arms stand on end, giving you goosebumps when you're cold or moved by music.
Why it matters
Its opposite, the calming parasympathetic system, is largely run by the vagus nerve. The balance between them shapes how your body responds to stress.
Nearby
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Sources
Drafted with AI help; awaiting a human fact-check against these sources.
Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.