In Japanese, a large number of verbs come in transitive/intransitive pairs. English has a few similar pairs: to fall / to fell s.th., to lie / to lay s.th., to sit / to set s.th., etc. The transitive verbs usually have a "causative" flavor (to fell a tree = to make a tree fall). So: Xを上げる (transitive), 上がる (intransitive) Xを下げる (transitive), 下がる (intransitive) 上る is just another way to write 登る (noboru), so it's a different verb.