Raising My Hand

You know what I hate?  When teachers don't call on you even though your hand is raised.  It's just really frustrating when you have your hand raised for five minutes to ask a question and the teacher just stares dead at you while continuing on with their lecture.  I think teachers do this purposely just so our arms get tired and we give up and then never get a chance to ask our question.  But if this is true, and my question is "Can I go to the bathroom?" they can't get mad when I just get up and go without their permission.  It wouldn't happen if they just called on me.