In mammalian body, this element plays numerous important roles. Try to identify this element with the fewest number of clues. This element is needed to insure the integrity and permeability of cell membranes, to regulate nerve and muscle excitability, to help sustain normal muscular contraction, and to assure cardiac rhythmicity. It also plays a significant role in several of enzymatic steps involved in blood coagulation and is the most significant element of bone salt. Name this element.
ANSWER: Calcium