There's a genuine question of whether fully simulating a brain will be enough. We have several hundred million neurons in our digestive system. What we eat, and the kind of bacteria that lives there influences our mood. Same with the rest of our body. Brains are part of a larger organism. What would it mean to just simulate the brain independent of a body? Our sensory organs play a role in processing the incoming sensory stimulus and then send that off to the brain.