Good feelings from knuckle popping and head scratching, iin?

So I have this friend in high school who would pop my knockles for me about every week. The thing I find odd is that every time he does it I got this emensly good feeling along with an huge sense of complete carelessness that would come seconds after he finishes. It would leave me just sitting at my chair doing nothing, and thinking nothing, but enjoying the feeling of it for at least a few minutes. I also get the same good feeling, but with no sense of carelessness when I get a slightly rough scratch on the head, though it doesn't last longer than a few seconds afterwards. But I get nearly nothing when I do both on myself, which I expect is normal. So IIN?