Cordlike bundles of fibres that conduct impulses between the brain or spinal cord and another part of the body (5)
I believe the answer is:
nerve
(Other definitions for nerve that I've seen before include "Courage, like bodily fibre" , "Fibre carrying impulses from brain to body" , "Impulse transmitter - bottle" , "Mettle, daring" , "Courage - impertinence" .)