Does the peripheral nervous system have a system of routers that decide where a message is meant to go based on some kind of address, or does a signal from the brain follow a single, unbroken chain of neurons that starts at the brain and ends at one destination?
For example, let's say my brain wants to send a message to my left pinky, telling it to contract. In the first model, a series of action potentials travel down my spinal cord, reaching a node in my chest. The action potentials encode the "contract" command as well as an address. The node in my chest reads the address, and routes the signal down my left arm. It reaches my left hand, where another node reads the address and sends the signal to my left pinky, where the signal reaches the appropriate muscle, telling it to contract.
In the second model, every single muscle in my body has a particular chain of neurons that runs in parallel to my brain. If my brain wants to send that signal, it doesn't have to specify an address, it just sends the "contract" command down the path that says "Leads directly to left pinky and nowhere else".
If the second model is true, does that mean that the large, visible structures that we call "nerves", such as the vagus nerve, are actually bundles of point-to-point connections?
Anywhere I can find more information about this would be awesome. I'm a comp sci/biochem double major, and really love reading about the body as an information system.