Is it ensure, insure, or assure?
physiological phys·i·o·log·i·cal (fĭz'ē-ə-lŏj'ĭ-kəl) or phys·i·o·log·ic (-ĭk)
Of or relating to physiology.
Being in accord with or characteristic of the normal functioning of a living organism.
Relating to the action of a drug when given to a healthy person, as distinguished from its therapeutic action.