Ma'anar ƙamus na kalmar "tsarin jiki" yana nufin duk wani aiki ko aiki da ke faruwa a cikin jikin wata halitta mai rai, kamar narkewa, numfashi, zazzagewa, ko fitarwa. Wadannan matakai suna da mahimmanci don kiyaye aikin al'ada na jiki da kuma kiyaye shi a cikin yanayin homeostasis. Sauran hanyoyin tsarin jiki sun haɗa da samar da hormones, daidaita yanayin zafin jiki, da sarrafa bayanan azanci.