I’m currently attending some very specialized nerology classes (I’m a future surgeon!), and I got answers (not only suppositions).
Someone said before that a nerve is like an optic fiber, Wrong!
The nerve is a binary device: it can only transmit a voltage difference (wich is made by the K+/Na+ doors & pumps). At normal state, the nerve will have a -70mV potential. When it’s excited up to -55mV, the rection of the doors is unstopable and the potential go up to -30mV. After, the nerve just repolarize itself to -55mV, goes into an Hyperpolarisation (-90mV), and come back to normal. Here’s an ASCII graph to explain:
Voltage in fonction of time

........./--\ -Max polarisation (30mV)
......../....\
......./......\
.../--/........\ <-Max exitation reached: the signal goes on (-55mV) --/.............\....../----- <-Normal state (-70mV) .................\..../ ..................\--/ <-Hyperpolarisation (-90mV) 0ms TIME 4ms 5ms

This whole process cannot be modulated: It's on or off, you can't mess with the voltage of the reaction. So the signal is binary: 1 or 0.

You'll see too that the time of the whole process, before it can be done again, is about 4ms, which mean low BitRate, and a lag of about 1-2ms minimum (before it reach the top of the curve).

The fastest nerves have a frequency of about 200Hz to 300Hz, wich mean that on a single fiber, you can only do 300bps MAX (remember those accoustic modems?)
The next problems with nerves as a data transport: they're slow. The fastest nerves can go at about 280mph (wich is only a little faster than a F-1). This mean that if you carry data over 130m of distance, you'll get a 1000ms lag!

Too: Your network will be limited to a 1 meter cable. The longest nerves (in the legs) are about 1 meter long, and if you plan putting some of them together, you add some lag time when they interact (about 2-4ms)

Other problem I see with nerves: they're alive. You need to feed them in nutriments, oxygen and oligoelements (most K/Na/Ca). This mean putting blood vessels along them. But you'll need the nevroglious cells!! For normal nerves, only Schwann cells are required, but you'll need to be sure they're in large number enough to produce the myelin gain. You'll need to feed them too.

The last one: nerves don't regenerate, and they don't reproduce. So, if you go to the top 300bps for too long, your cells might dies, and they'll nerver be replaced. The axon (the long tail) CAN regenerate, but it take time (some months). If one of the cells die, you can say good bye to your device (or replace THE faulty nerve, and hope that no others will die for the next hour).

All the numbers said here are optimals. You shouldn't dream of a 1meter long, 4msMin.Time, 300Hz, 280mph nerve, it won't happen. You can have one (or maybe two) of the optimals factor, but you'll be lucky. Don't even speculate numbers for the "Perfect nerve", it just isn't real.
Unless you want to imbed something into someone, mess with copper and optic, leave nerves to neurosurgeons and bioengineers.

---Jérôme "Future geek/surgeon multiclass" Marchand