Brain which side are u on?

i have been teaching math [which i have to learn again]. i'm interested in whether the exercising of that side of the brain will have any affect on the other side, and whether it will affect how i write? i notice after i have figured out a few problems my brain really hurts, kind of how your body hurts after a good physical workout; a not too unpleasant experience. i wonder if the brain releases endorphines after/during mental exercise? I'll have to tell u my button up my nose story one day.