The chairman shall preside at all meetings and shall perform such duties as are imposed upon him by law or by action of the board. The vice-chairman shall perform the duties of the chairman if there is a vacancy in the office of the chairman or in case of the chairman’s absence or inability to act. If there is a vacancy in the office of the chairman and vice-chairman or the chairman and vice-chairman are absent from any meeting or refuse to perform their duties, a chairman pro tempore shall be appointed by the board from among their number.
     The secretary shall perform the duties usually pertaining to his office. If he is absent from any meeting or refuses to perform his duties, a member of the board shall be appointed secretary pro tempore.