Depending on the elasticity of the brain, brain damage can make other parts of the brain take over for damaged areas (after a terrible recovery process).

In fact, it's possible for a brain to be almost entirely empty space and people learn about it decades into their normal lives.

There are regions inside the brain that usually take care of certain functions but it's not like there's a specific area that's guaranteed to be designated to specific nerves. Every brain is different, the schematics are generalisations that'll work well enough most of the time.