after straightening my hair or trying something new, i've often felt this way as well. i felt like it was so damaged that i would have to cut it all off. but in the end i didnt have to. it could be a fewthings. maybe there are still split ends left, but another thing that could make it feel this way are knots. these often happen farther up the strand than splits, so they could be missed by a trim. cut them out if you see / feel them!
if you've checked your hair for knots and can't find any, it may just be that your hair is very dried out from the flat iron. i've never flat ironed my hair at 410, but here's what i do when my hair is super dry from a flat iron. COwash your hair and do a DT. moisturize your hair as normal and see if it's better. your hair may still not completely revert (looser than normal curl), but thats normal. i would worry, however, if you had bone straight pieces. but the looser curls should hopefully be back to normal after a few more washes. if its stilll dry, do a nightly DT (oil or conditioner) for a couple of weeks until your hair feels better. HTH...