Section 90J. In any city, town, county, district or authority retirement system accepting the provisions of this section, the retirement system shall pay the costs for the annual physical and mental examination of any member serving beyond age seventy pursuant to the provisions of section ninety F, ninety G or ninety H. Such payments shall be made from and charged to the expense fund of the system. Acceptance of this section shall take effect by majority vote of the retirement board, subject to the approval of the local legislative body. For the purposes of this section, legislative body shall mean the town meeting for the purposes of a town system, the city council subject to the provisions of its charter in a city system, the district meeting in a district system, the county commissioners in a county system, and the governing body of the authority in an authority system. Acceptance shall be deemed to have occurred upon the filing of a certificate of acceptance with the commissioner.