After a poor start on offense and defense, it seemed as if the Falcons flipped on a big switch on the gigantic scoreboard at AT&T Stadium.

Instead of getting run over on defense and stymied on offense, the Falcons thwarted the host Cowboys and starting scoring in bunches. The Falcons (3-0) hope they have a more consistent showing when they face the Houston Texans (1-2) at 1 p.m. Sunday at the Georgia Dome.

Defensive coordinator Richard Smith and offensive coordinator Kyle Shanahan turned in fine showings with the aid of the assistant coaches with their in-game and halftime adjustments.

“The adjustments in this league are made on the sidelines, immediately. The minute that there is an issue we fix them,” Smith said. “Players had heard it from the assistants on the sidelines. When we got in there (at halftime). We talked to them and showed them, these are the plays we need to fix. (Here are) the issues. We are better than what we’ve proven. Let’s go out and get it done the right way.”

After giving up 131 yards rushing in the first half, the defense held the Cowboys to minus-4 yards rushing. They attacked the gaps harder to the ball-side of the field, and the linebackers dropped back off the line to get better angles. Also, because Cowboys quarterback Brandon Weeden didn’t want to throw the ball downfield, the Falcons positioned safety William Moore near the line of scrimmage.

“The players responded extremely well,” Smith said.

Shanahan had his problems, too.

The Falcons were forced to punt on three of their first four possessions as the Cowboys built a 28-7 lead. After he made adjustments in the run game to break Devonta Freeman loose, the Falcons scored on five of their next six possessions.

“He has such a knack of how to attack, and he can go from one play to the next play, set one up, go to the next one, and I think it’s one of the real gifts for him,” Falcons coach Dan Quinn said of Shanahan. “During all of the chaos of a game, he’s able to keep the focus where some people can’t.”

Unlike Houston, which has mega-defensive star J.J. Watt, the Falcons have a committee approach to defense.

Smith and Quinn are using all nine defensive linemen, have found a trusty nickel back in Phillip Adams and have asked inside linebacker Nate Stupar to help out at strongside linebacker.

“When we went in at halftime, we were disappointed, but nobody had their heads between their legs,” Smith said.

Stupar has turned in some solid play over the past two games at strongside linebacker.

After not playing from scrimmage against the Eagles, he played 32 percent of the snaps against the Giants and 28 percent against Dallas.

“The one interception that put our offense in the red zone really, what happened was, we were able to flush the quarterback out of the pocket and Stu was able to get the hit on him, which created the interception,” defensive coordinator Richard Smith said. “That was a great play.”

Stupar, 27, has been an inside linebacker for the Falcons and played primarily on special teams in 2014. He has played in 30 NFL games, mostly as a special-teamer, and has spent time with the Raiders, Eagles, 49ers and Jaguars.

Once Freeman got rolling, then things opened for wide receiver Julio Jones, who finished with 12 catches for 164 yards and two touchdowns.

Shanahan moved him around the formations and even slipped in the backfield in the I-formation behind Freeman.

After the game, Jones called Shanahan a “genius” for helping him get open and so he could be productive.

“That’s a great compliment, but he makes it pretty easy,” Shanahan said.

While Shanahan has been able to get Jones free, the franchise’s all-time leading receiver, Roddy White, has disappeared from the offense after catching four passes for 84 yards in the season-opening win over the Eagles.

“It doesn’t always show up on the stat sheet, but I think Roddy had his best game last week,” Shanahan said. “He only had one opportunity, but it got called back. I thought he did a heck of a job. He had the best game blocking of all three of (the wide receivers). When he did have his routes, he got open.”

But you can tell that Shanahan has just started to have fun with Jones and his wonderful blend of speed, power and toughness.

Shanahan noted that he’s had some very good receivers before, such as Andre Johnson and Pierre Garcon, but Jones may be a cut or two above both of them.

“The one thing with Julio is that he can run the entire route tree,” Shanahan said. “When you have a guy as talented as him and he can run the entire route tree, it makes it very easy to move the ball over because he’s capable of doing it all.

“It really doesn’t matter what we ask him to do. We try to keep him fresh and keep him moving around.”

Quarterback Matt Ryan is pleased with how the offense is moving along under Shanahan.

“He’s on point, and it’s a good time to be a part of that,” Ryan said.

Smith pointed out that guidance from Quinn was a big part of implementation of the adjustments.

“It’s a credit really to coach Quinn and how he’s emphasized finishing and the competition thing,” Smith said. “It’s a credit to the players. It’s great, the attitude of hey, ‘we’re never out of it.’ Anytime that you’ve got that on your side, great things can happen for you.”

That’s why the Falcons became the first team in NFL history to open the season with three victories after trailing entering the fourth quarter.