The business of medical service corporations shall be managed by a board of directors of three or more persons, the majority of whom at all times shall be licensed doctors of medicine and elected by the members and for the terms provided for in the bylaws; provided, however, if a medical service corporation shall operate in as many as six counties of this state, its board of directors shall consist of not less than five persons; and, if a medical service corporation shall operate in as many as 15 or more counties of this state, its board of directors shall consist of not less than seven persons. The medical members of the board shall be nominated by the medical societies in the county or counties in which the medical service corporation shall operate, and the other members of the board shall be representatives of the subscribers of the areas involved and shall be nominated by the members of the medical service corporation; and all members of the board shall be elected by the members of the medical service corporation as provided in this Code section. Directors shall serve without pay for their work in this capacity; however, they may receive pay for particular services actually rendered, such as legal counsel, medical or surgical service, accounting, or other required services upon specific approval of the board of directors, such approval being made a part of the minutes of the board of directors. A director shall have no vote on any matter in which he has a financial interest.