The board shall appoint an Executive Director who possesses the necessary qualifications and experience to enable him to carry out the duties required by his office. The Executive Director who may be a physician, shall receive a salary set by the board, subject to the approval of the State Personnel Board, and shall serve at the will and pleasure of the board. The executive officers shall be vested with all the authority of the board when it is not in session, and he shall be subject to such rules and regulations as may be prescribed by the board.