Is it sometimes overwhelming to see inside of a brain for neurosurgeon ?

Initially, it will be unnerving. It's like seeing a dead body for the first time. Like with anything, you'll get used to it after repeat exposure. My mom would joke how they would eat lunch next to the cadavers at the same time as analyzing body parts. This was in the 80s and things were always "go go go" in the medical field. So no time for lunch breaks. Either way, you probably won't even be bothered by the brain after a while.