President of the Senate
The President of the Senate (not to be confused with the President Pro Tempore of the Senate) presides over sessions of the United States Senate, although their powers are considerably less than the Speaker of the House. The president votes only in case of a tie. The position of Senate President is granted by virtue of office to the Vice President, although in practice, they rarely preside over Senate sessions, instead usually delegating to junior Senators, to allow them to learn Senate procedure. 
Under the Constitution, the Vice President serves as President of the Senate. He may vote in the Senate in the case of a tie, but is not required to. The President Pro Tempore (and others designated by him) usually perform these duties during the Vice President's frequent absences from the Senate.