Actually the speed of nerve impulses is irrelevant to the whole question -
which is what makes the assertion in Jurassic Park so silly.  Neurotoxins
affect the nervous system, but they do not travel through the body via the
nervous system.  They are transported from the site of injection via
diffusion through surrounding tissues, and via the blood stream.  In one
two-thousandth of a second, a toxin, no matter how virulent, could not move
more than a fraction of a millimeter from the site of injection, even if it
was injected directly into an artery! Even a bite from a king cobra won't
kill you in a fraction of a second! :-)

Paul M.