Nervous system
From Tardis Wiki, the free Doctor Who reference
A nervous system was a being's network of nerves and axons that enable control of the body.
The Third Doctor speculated that the Nestene creature in Channing's tank was a kind of brain or nervous system, humanly speaking. (TV: Spearhead from Space)
Sutekh said he could shread the Fourth Doctor's nervous system into fibres and draw the pain out for centuries. (TV: Pyramids of Mars)
The Hoothi infected other creatures, usually having better control over ones with more complex nervous systems. (PROSE: Love and War)
