Don't know if everyone is interested in some of this, but take it with a grain of salt--I never knew alot of this stuff.  This is a boiled down versus (in my own words--hope it makes sense) of alot of the information I read on several sites.  I tried to include only what I read that was similar in a couple of places.

1. Question - When they heard what and who were the "they" in that verse?

Per the King James version: 

But the high priest came, and they that were with him, and called the council together, and all the senate of the children of Israel, the captain of the temple and the chief priests, and the officers of the temple.

The Great Sanhedrin was the legislative body and Supreme Court of Israel. It had 71 members in it. Based on Torah records, Moses established the Sanhedrin as commanded by God. "Assemble for me seventy men of the elders of Israel, whom you know to be the people's elders and officers, and you shall take them to the Tent of Meeting, and they shall stand there with you." It also describes that Moses laid hands (semicha) on Joshua and "commissioned" or ordained him as directed by God. This is an outward sign of giving God's authority to Joshua. Moses also ordained the 70 elders. Ordination was the method used to replace any members who become unable to do their duties as an elder. It did not require the placing of hands on an individual, but to have semicha authority (laying on of hands) an individual had to be ordained by another semicha ordained rabbi. The title rabbi was held for those who had semicha as the method of ordination. This is considered the beginning of the Rabbic service. The Sanhedrin was a mix of political and religious power. They meet everyday except for the Sabbath and festival time. They made the over all law on Jewish life. They had power that the lower Sanhedrin did not have such as: they were the only one who could bring the king to trail; extend boundaries of the temple; and gave final decisions on questions of law. The line of authority came from a direct chain from Moses through semicha ordination until the Sanhedrin was dissolved by the Roman empire.

The leader was the High Priest, called Nasi or prince (after the creation of the office of Nasi was created) or Cohen Gadol; a vice chief justice, who was also called the Av Beit Din or Head of the Court- like our vice president-which sit over criminal trails; and 69 members. The first head of the office of the Nasi was a Hillel the Elder. Ater Hillel one of his descendants was over the Sanhedrin. All the judges must convene for national matter, but 23 members can be used to answer questions on law points. If the 23 cannot agree-then the 71 must meet.

The Gospel makes a distinction between the Pharisees (believe in afterlife and they accepted the Priest’s statements on law) and the Sadducees ( did not believe in afterlife with God, resurrection, they believed in power of selves.) During the time of Jesus the Sadducees seems to be in charge of the council. The Gospel also makes distinction between the elders, the politicians, and the lawyers. Secular teachings would divide them into religious and non-religious.

This is where Jesus was brought to stand trail before the council. This is one of the sticky points between Christian and Jews. The Sanhedrin could not find reason to punish Jesus--so they produced witnesses to accuse Jesus of blasphemy-a capital crime under Moses law. The Sanhedrin could not condemn criminals to death so they took him before Pilate, who had Roman authority to sentence him to death. When Jesus claimed to be the Messiah he broke Roman law, which viewed it as treason to the Roman Head Authority--but under Jewish law this was not illegal. Many claimed it during this time--only Jesus paid the price for it. Pilate didn't want to condemn, but was afraid of a revolt by the Jews-so he sent Jesus to the cross, but we all know it wasn't him that allowed it to happen. It was our heavenly Father making a way for us. Jewish sources state that this did not happen because the council did not meet during festivals or holidays. Some Jewish accounts also state that this portion was not written when it happened but years later when the Christians were accepting the Gentiles into their group. That Christians recorded it as it is in the Bible to make it more sympathy to those they are ministering to--the Gentiles.

Roman authority declared it a capital offense for the Sanhedrin to assemble and declared ordination illegal. Their law prescribe punishment for any Rabbi who received ordination. It also required the complete destruction of the city where it occurred. the position of Nasi became illegal and with the death of the last high priest the tax collected by the Sanhedrin was diverted to the Imperial treasury. The council was dissolved.

V.34 - "Then one in the council stood up, a Pharisee named Gamaliel, a teacher of the Law held in respect by all the people, and commanded them to put the apostles outside for a little while."

Per the King James Bible -- The teacher of Paul Acts 22:3 (King James Version)

3 I am verily a man which am a Jew, born in Tarsus, a city in Cilicia, yet brought up in this city at the feet of Gamaliel, and taught according to the perfect manner of the law of the fathers, and was zealous toward God, as ye all are this day.