Section 5. There shall be a sangguniang barangay in every duly constituted barangay which shall be the legislative body and shall be composed of seven (7) kagawads to be elected by the registered voters of the barangay. The candidate who obtains the highest number of votes shall be the punong barangay and in the event of a tie, there shall be a drawing of lots under the supervision of the Commission on Elections. The chairman of the kabataang barangay who shall hereafter be elected in accordance with law shall be an ex officio member of the sangguniang barangay. In the event of any vacancy in the office of the punong barangay, whether temporary or permanent, or in case of disqualification or refusal to assume office, an order of succession among the six (6) members of the sangguniang barangay based upon the number of votes received from the highest to the lowest shall be followed to fill up the vacancy. In default of any duly elected member of the sangguniang barangay, the vacancy may be filled up by the city or municipal mayor concerned.