Your problem isn't introversion, as noted, but what is called the "fixed mindset", by Carol Dweck. You're more interested in proving yourself, showing your own brilliance, and when you can't you close down and turn inward to avoid having to allow yourself to be seen as ignorant or uncertain.
The reverse is the growth mindset, which is based on the assumption that it is always possible to get better at anything, and as a result, it's okay to make mistakes and look stupid, because then you have opportunities to learn.
Learn how to say, "I don't understand," and "Could you explain that?" Learn how to say stuff that sounds stupid to you: it takes some impulsiveness, but it can be done. If you're dead wrong, you'll find out. If you're right, you'll look good. If neither of you have any idea, hey it's more to talk about.