LOS ANGELES (AP) -- Zachary Quinto does a fine Mr. Spock on screen, but the new "Star Trek" co-star isn't sure what sort of Vulcan he would make in real life.

Vulcans control their emotions, and that's something Quinto acknowledges he does not do among those closest to him.

"People that know me in the most intimate way and my most inner circle of friends and family and relations know me to be pretty expressive and pretty articulate about how I'm feeling," said Quinto, who landed the role as the new Vulcan brainiac Spock in director J.J. Abrams' update of the franchise. "I like to talk about that kind of thing."

Alongside Chris Pine as the new James Kirk, Spock's best friend and captain on the starship Enterprise, Quinto has inherited one of the most beloved characters in science fiction. Among the many alternations in Abrams' updated "Trek" universe, there's brashness and tenderness amid the new young Spock's logic and reason.

While Quinto's half-human, half-Vulcan Spock does not necessarily like to talk about his feelings, he definitely has them, revealing his emotions in a passionate and even fierce manner that Leonard Nimoy's Spock rarely got to do in his decades with "Star Trek."

Even so, Quinto has to keep his emotions in check for most of the movie. Quinto said it was the hardest part of his job on "Star Trek."

"To feel and to create a charged internal emotional life and to have to hold it, to have to hold both ends of it and really not give any of it away, that for me, who's a pretty emotive person in my life, was a challenge," Quinto said. "Especially when the rest of the cast didn't have to abide by such restrictions."

Actually, one other cast member had to abide by the same rules. Nimoy returns as the older Spock, playing most of his scenes with Pine's Kirk but sharing some moments with Quinto toward the end.

Nimoy said he felt almost a "father-son relationship" with both Quinto and Pine. Whether or not Nimoy appears in future "Trek" movies, he said Spock was in good hands with Quinto.

"He's well-trained, he's very intelligent, and he projects an inner life which I found useful in the character, and I was very comfortable with that," Nimoy said.

Before "Star Trek," Quinto, 31, mostly had credits in live theater and television. He had a recurring role on "24," co-starred in the short-lived Tori Spelling comedy "So noTORIous" and is best-known as the mysterious serial killer Sylar on "Heroes."

Nimoy's character, dubbed "Spock Prime" in the credits, is a centered, stately figure, at peace with the conflict between his emotional human half and his logical Vulcan side.

Quinto's younger version, though, is a more volatile figure, involved in a surprising relationship with a crew mate and unable to fully control himself after personal tragedy strikes.

"He's much more unstable. He's much less comfortable with the duality that exists within him," Quinto said. "He's much more pulled in different directions. That for me as an actor is really rewarding."