Sympathetic nervous system
The sympathetic nervous system was one of three major parts of the autonomic nervous system.

In 2371, while massaging Kes' feet as part of the rolissisin ritual, The Doctor reasoned that stimulating the sympathetic nerves set off a hormonal reaction which activated glandular activity in the tissues of Kes' tongue, causing it to swell. ()

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de: Sympathikusnerv
Biological systems