LAKE FOREST, Ill. – Week by week, the buzz is building. It’s getting loud enough to jog memories of the team that shuffled to the championship, even if the Super Bowl is months away.

The volume was high after the Chicago Bears beat the Buffalo Bills 40-7 to improve to 5-0 Sunday. The contributions came from four areas: a defense that fell about a minute shy of a shutout, an offense that clicked again, and special teams units that were solid as they can be.

The fourth area?

“The fourth, our home-field advantage, was outstanding,” coach Lovie Smith said.

Chicago is 5-0 for the first time since 1986, when it won its first six, but the Bears are stirring memories of 1985.

That team, with one of the greatest defenses ever assembled, allowed 88 points through the first five games while scoring 163. The current Bears have held opponents to a league-low 36 points while scoring a league-leading 156.

That’s right, a franchise that has historically relied on defense and the running game is leading the NFL in scoring behind healthy quarterback Rex Grossman and the emerging Bernard Berrian, the league’s third-leading receiver with 413 yards. And the running game seems to be on track after three sluggish games to start the season.

Meanwhile, the defense is on pace to smash the record for fewest points allowed in a 16-game season – 165 by the Baltimore Ravens five years ago. That’s not shocking. Chicago had the league’s stingiest defense last season and won the NFC North.

“During the game, it’s a little surprising because you don’t expect to do that in the NFL,” linebacker Brian Urlacher said. “We just keep making plays when we have to. We are going to be in some close games. Not every game is going to be like this. We understand that, but we’ll take as many as we can get.”

Defensive end Adewale Ogunleye and defensive tackle Ian Scott sat out with hamstring injuries. Smith said he doesn’t “know for sure” if Ogunleye will play Monday at Arizona, but expects Scott to be ready. And free safety Chris Harris is questionable after pulling a quadriceps on Sunday.

Even with two starters on the defensive line missing, the Bears held Buffalo to 145 yards and were closing in on their second shutout before J.P. Losman connected with Lee Evans for a 5-yard touchdown with 1:06 remaining.

Although that rankled the defense, there was little to criticize.

The Bears’ special teams forced two turnovers, and Robbie Gould made all four field goals to improve to 17-of-17 this year.

Thomas Jones rushed for a season-high 109 yards after running for 98 the previous week against Seattle, and Cedric Benson carried 14 times for 48 yards and his first two NFL touchdowns.

The Bears took big strides on the ground and continued to make big plays in the air.

Grossman threw for 182 yards and the two touchdowns before sitting out the fourth quarter and continued to provide the element the team lacked in the past, connecting with Berrian for a career-long 62-yarder. It was the fourth game this season in which he had a completion of 41 yards or more.

“Anytime you play like that, it’s so much fun,” Grossman said. “All your hard work coming together and everyone playing the way they’re playing, it’s fun to see teammates make a bunch of plays. It was just a blast out there.”

Still, Smith’s optimism is guarded.

“My glass is half-full most of the time,” he said. “I see a lot of other good things that could happen. Yeah, the sky can always fall, but I know the things we can improve upon. And I’m anxious to … see exactly how good this team can be.”