Sections 390.31 to 390.35 apply only to counties in which the county board elects to be bound by them in lieu of other law relating to coroners. In a county in which sections 390.31 to 390.35 apply, the county board may by resolution resume death investigations under sections 390.005 to 390.25. The board shall then fill the office of coroner as provided by section 390.005.