The term Patrician referred to those members that were of the ruling class of Ancient Rome. They were the ones who derived from the old ruling elite and Senatorial families. We know that according to Roman Tradition Romulus himself created and divided the Patrician class, also showing their own self-importance that they were instituted by the divine Founder of Rome and it is generally accepted that they formed the ruling elite of Rome; particularly those in the Senate. We also know that the Patricians were members of a select group of families and to be a Patrician you needed to be from one of them. And it is from here that we can begin to see the actions done by the Patricians that would cause the Plebs to rise up against them.
FUELING THE FIRE
In an eager attempt to control and monopolize their power the Patricians closed off their positions and class. They sought to make sure that control of Rome remained firmly in their hands. Richard Mitchell (Social Struggles) points out that this just marked the beginning of the wrongs Plebeians would cry out were committed against them by the Patricians. He notes that Patricians and Plebeians were united in revolting and throwing out the Tyrants that existed before the Republic. But once the Tyrants were rid of, the Patricians treated the Plebeians much in the way that they had been treated by the Tarquins. The Patricians proceeded to close off the Magistrates, Judicial positions, and Priesthood to solely themselves. In this case the Patricians are thought to be more of an aristocracy than to be merely wealthy noblemen. Something to keep in mind however is that the Rex and Military Tribunes were still open to be held by Plebs. In whole though once the Tyrants fell it was the Patricians that seized the opportunity and prospered. Rome became an aristocratic ruled city not a democracy open to all people.
To further enrage the Plebeians certain laws were passed that attempted to maintain the status quo sought by Patrician rulers. For instance a non-Patrician could not marry into the families. The system of laws existed at the time that were emplaced were highly unbalanced and favored Patricians over Plebeians. They did not grant equal rights to all citizens. The laws should be thought of as more of a code as well than rather an actual system of legal principles (Momigliano). The Patricians also sought to control their place economically through actions such as debt-bondage. This would be an area of major assertion by the Plebs in their demand for social and economical justice.