From my experience, there are too many persons who suffer with this condition and don't get help, and too few professors who don't know how to help someone overcome it. Many thanks to all those who talked with me about this situation from both sides of the seminar table. Take care of your body. Regular exercise reduces your heart rate. Caffeine and junk food increases it.
Excessive smoking restricts blood flow.
Try to eat something healthy before a class or a presentation so that your blood sugar level is normal. Let your instructor know. Have potential questions and comments written out ahead of time. Don't be hesitant to read from a paper or notebook. Jump ahead of the pack.