Colin Kaepernick threw for two touchdowns in his first career start and a smothering San Francisco defense gave the 49ers an emphatic 32-7 win over the Chicago Bears on Monday night.

Playing in place of an injured Alex Smith, who is suffering from a concussion he sustained in last week's tie against the Rams, Kaepernick went 16-for-23 for 243 yards and led the 49ers (7-2-1) to scores on their first four possessions.

Smith passed the NFL's ImPACT testing protocol and was able to practice in a limited fashion by Thursday. He reportedly planned on playing Monday night, but was ruled out earlier in the day after being evaluated by 49ers medical director Dr. Dan Garza.

The San Francisco defense, meanwhile, held the Bears to just 151 yards and pummeled Jason Campbell all game. Second-year linebacker Aldon Smith posted 5 1/2 sacks, and the team finished with six along with two interceptions and a safety in the win.

San Francisco head coach Jim Harbaugh was on the sidelines after being sent to the hospital last Thursday with an irregular heartbeat. He had a cardioversion procedure done on his heart, which is an electric shock that restores the heart's normal rhythm, and was back on the practice field on Friday.

"I thought he did a great job and showed a lot of poise in the pocket," said Harbaugh about Kaepernick. "He found his receivers and acquitted himself fantastically out there. There was a lot of good things about this game, especially the defense which had a great night."

Campbell made his first start of the season in place of Jay Cutler, who suffered a concussion due to a helmet-to-helmet hit from Houston linebacker Tim Dobbins in last week's loss to the Texans. Campbell, though, didn't fare nearly as well as his counterpart, as he went just 14-for-22 with 107 yards and a touchdown along with the two picks for the Bears (7-3), who dropped their second straight to fall into a tie with Green Bay for first place in the NFC North.

"It definitely wasn't the way we prepared all week," said Campbell. "You never want to come out and have this kind of performance, but give their defense credit because they came out hard and kept it up. Tonight was probably the worst nightmare."

The Niners started the game with the ball and Kaepernick went right to work with an 8-yard pass to Mario Manningham that saw the team get another 15 yards on an unnecessary roughness call on Chris Conte for a late hit on Manningham. The drive stalled in the red zone, but a 32-yard field goal from David Akers gave the team a 3-0 lead.

Chicago went three-and-out and San Fran struck quick. On the third play, Kaepernick went deep down the right sideline and hit Kyle Williams in-stride for a 57-yard pickup. On the next snap, Kaepernick found Vernon Davis in the end zone on a 3-yard score and a 10-0 lead with 6:14 to play in the first quarter.

The Bears got a couple of first downs on their next touch, but had to punt and the 49ers got the ball back at their own 4-yard line. Frank Gore took the first snap 13 yards and Randy Moss followed with a 12-yard catch. Davis made a 32-yard grab on the first play of the second quarter to get the ball past midfield. Four plays later, Kendall Hunter took a handoff up the middle and into the end zone on a 14-yard score for a 17-0 advantage.

Tarell Brown jumped the route on a Campbell pass for the pickoff and took it to the Chicago 44. That led to a 37-yard field goal from Akers and a 20-0 lead with 6:32 to play in the half.

San Francisco kept its foot on the pedal coming out of the break as the team held Chicago to a three-and-out and went back to work.

Starting at their own 38, Gore ran for 11 yards and Manningham followed with a 37-yard catch down to the 14. Two plays later, Kaepernick found Michael Crabtree in the left corner of the end zone for a 10-yard score and a 27-0 lead.

Chicago finally put together a successful drive as the team got across midfield for the first time and made it into the end zone. On the 13th play of the 74-yard march, Campbell lofted the ball to the right corner of the end zone and Brandon Marshall came down with it for a 13-yard catch and a 27-7 game with 3:43 to play.

San Fran then went three-and-out and Chicago got the ball back, but Dashon Goldson picked off Campbell and Akers hit a 32-yard field goal with 11:46 to play.

The 49ers added a safety two minutes later as Campbell fumbled the ball in the end zone as he was tackled. The ball was recovered by guard Chilo Rachal and he tried to pass it out, but he was tackled in the end zone. Initially the play was ruled as an intentional grounding, but a replay showed that he was tackled and the safety was awarded.

Game Notes

Gore finished the game with 17 carries for 78 yards ... Matt Forte led Chicago runners with 21 carries for 63 yards ... Davis led all receivers with six catches for 83 yards ... Chicago hosts Minnesota on Sunday ... The 49ers play in New Orleans on Sunday ... The Bears had won three of four against the 49ers coming into the game ... San Fran totaled 355 yards.