The Senate's role, contributions and impacts during the Julio-Claudian era:

In theory the Senate was a purely advisory body, but in practice it became a governing body in Rome. It was the legislature, executive and judiciary, all rolled into one. It was a permanent body with ultimate control in Rome and it governed Rome until 133 B.C., virtually unchallenged. The Senate had been able to obtain this enormous power because of the policy of greedy imperialism pursued by Rome, resulting in vast territorial expansion and …

…to debate freely. Later Nero's policies changed and a number of prominent senators and wealthy people were murdered. Nero also re-introduced treason trials to get money from the senatorial class. By the end of the Julio-Claudian period the Senate had become almost irrelevant, holding barely any of it original duties or prestige. The Senate had become an "apathetic body" ruled by factions. Much of the respect that once stood for the Senate was now non-existent.