When a Hollywood actress turns 40, the stream of job offers can turn into a trickle.

Mary McDonnell hasn’t faced such an experience.

The actress, whose film breakthrough came in Dances With Wolves (1990) and who is also known forIndependence Day (1996), is 61. She’s not only still working, she’s starring in one of the biggest hits on cable television, playing Capt. Sharon Raydor on TNT’s Major Crimes, a spinoff of the hit The Closer (2005-12).

“I’m not 25; I’m not even 40,” McDonnell said by phone from the set of Major Crimes, which will begin its second season tonight.

“In my mind, I still feel the enthusiasm of 25. I still feel the same drive about life. I work hard so the body can match that energy.”

The actress begins each day with a swim, leaving her fresh and energized to play Capt. Raydor, a hard-driving authority figure whom viewers first met as the whip-cracking boss of the unorthodox Deputy Police Chief Brenda Johnson (Kyra Sedgwick) on The Closer.

On her own show, a deeper, richer portrait of Raydor has emerged. Still, she hasn’t become any softer or squishier.

“It’s such a revelation and so refreshing that she’s a female captain and a woman of power,” McDonnell said.

McDonnell thinks she knows why Raydor has struck such a positive nerve.

“This character celebrates smart women,” she said. “Like so many of us, she is very competent in her own skin, although there are dysfunctional things in her life. She also is having a good life and has a strong ethical code.

“There isn’t this crazy darkness that a lot of cops carry with them. This is a woman like many women I know: She gets the job done.”

Portraying someone so competent isn’t necessarily easy, she said.

“Bad is easier. It’s flashier. This is about playing strength.”

The series, which premiered in 2012, was a hit immediately.

“Without a doubt, it was such a success that we broke records,” McDonnell said. “The fans really backed the faith I had in this show. They gave us a strong start.”

The success was a relief to McDonnell, who hadn’t carried a series. The closest she had come was playing President Laura Roslin in the ensemble cast of Battlestar Galactica (2004-09).

“I didn’t have any fears about the quality of the show,” she said, “but I had the normal fears of success: Could I pull it off?”

Women 40 and older, the actress said, have particularly embraced the show.

“At this point in my life, I organically understand this woman I play,” she said. “There are a lot of women like her and me in the world. We’re women who have varying degrees of power, dealing with sophisticated situations. “After 40, it’s about how do you get clear and practice living a great life?

“TV watching is becoming more important than ever as the baby boomers age,” she added. “I like to be able to turn on the TV in my house and see adults approaching the next 30 years of their lives.”