Neural networks are based on human brains. So, how are they both different? It is a very hard question, because if we would understand better the brain we will

Neural networks are based on human brains. So, how are they both different? It is a very hard question, because if we would understand better the brain we will simulate it better in the computers, how do we know we are not already doing a good simulation of the brain? Any answer to this question would be a step forward to improve our artificial intelligence systems.