I think we understand these systems well enough to know that just having knowledge about them isn't enough. We have experience with them going wrong in humans. You can lose the ability to feel pain if the physical structures that enable that are damaged. Knowledge won't help you there, no matter how much you have, if you don't have working nerves. Now, it might be possible to design something in an AI that mimics those systems, but I think that would have to be a very intentional act. It couldn't just be something that happens when the AI has learnt enough about pain unless it also has the ability to alter its own systems and decides to design such a thing for itself.