According to Osho, body and sense functions are called karma because even when egoic 'I' is absent—sleep, trance—their activity is sustained by your own deep life-urge (jeeveshna) and unconscious will. Outwardly we label egoless activity as kriya, but essentially all doing arises from your inner continuity of desire; therefore every activity, natural or deliberate, is your karma.
Even your automatic body processes happen because a deep wish to live moves them, so they’re part of your karma too.