Mayim Bialik’s career has gone through several phases since she burst onto the pop culture radar as the lead of the 1990s NBC series “Blossom.”

After the show wrapped, she earned her doctorate in neuroscience at UCLA while marrying and becoming the mother to two sons. Now she has returned to the small screen as a regular on the CBS sitcom “The Big Bang Theory.”

If the task of transitioning from child star to working adult actor wasn’t time- consuming enough, she also blogs regularly at the Jewish parenting site Kveller.

And she’s added yet another title: social justice activist. On Monday, Dec. 19, Bialik will host a fundraiser for Rabbis for Human Rights of North America that will honor clergy members who have stood out for their devotion to justice. Rabbi Israel Dresner, the “most arrested rabbi in America,” is among the honorees.

Mayim Bialik as Amy Farrah Fowler in TV series “The Big Bang Theory” photo/sonja flemming/ 2010 cbs broadcasting inc.

Bialik, 36, acknowledges that she was unfamiliar with RHR until she was contacted by Rabbi Jill Jacobs, the agency’s executive director, about emceeing the event. Yet after a little online investigation, she discovered that she was already connected to RHR.

“I went to the website and saw that my rabbi from UCLA, Chaim Seidler-Feller, was there,” Bialik said. That sealed the deal.

“We were looking for someone who is known for being deeply committed to Judaism and deeply committed to justice,” Jacobs said.

Bialik credits her Jewish upbringing with her lifelong devotion to performing good works. Last month, she spoke at an Exploring the World of Judaism event at Congregation Shir Hadash in Los Gatos; the title of her talk was “The Universal Values of Jewish Parenting.”

“I was raised in a very vibrant Reform community in Los Angeles,” she said. Temple Israel, the synagogue she attended as a youth, was “very tikkun olam based.”

As an adult, Bialik has worked with the Los Angeles–based Jewish Free Loan Association, helping to found a branch of the organization aimed at encouraging young professionals in Southern California to become involved in philanthropy.

“It’s a cause close to my heart,” she said. Yet her involvement has shown her just how difficult it is to get that demographic to participate. “People think, ‘When I’m older I will donate,’ ” she observed.

In addition to her work in social justice, Bialik also has become something of a spokeswoman for a more observant lifestyle. As a student at UCLA, she began moving toward greater Jewish ritual observance, including an increased emphasis on kosher (not too hard for the mostly vegan actress), Sabbath and modest dress. She explores these topics and others with candor on her Kveller blog. Her bachelor’s degrees from UCLA in 2000 were in neuroscience and Hebrew and Jewish Studies.

For religious reasons, Bialik primarily wears skirts, which hasn’t been hard to manage in her current role on “The Big Bang Theory,” since her character wears loose-fitting skirts and layers.

“I could’ve been cast as many things in this incarnation of my career. I happen to play a character that producers like to dress modestly,” she said of the bookish Amy Farrah Fowler, who is the love interest of uber-geek Sheldon, played by Emmy-winner Jim Parsons. “Thus far I have not been in a miniskirt.”

Yet despite hewing ever more closely to religious law in her personal life, Bialik refuses to identify fully with Orthodoxy. She has written forthrightly about having to work on Jewish holidays. And a future role might demand a more immodest wardrobe.

Yet when she can, Bialik goes to great lengths — quite literally — to observe. She agonized over her choice of Emmy dress (on her Kveller blog, she described her mission as “Operation Hot and Holy”) before settling on one that met most of her modesty requirements: covered arms and knees, with a hint of collarbone and cleavage.

She felt validated when she later saw Paris Hilton in the same dress in People magazine, with the suggestion that “you don’t have to show tons of skin to be sexy.”

Perhaps the editors at the celebrity magazine have been reading Bialik’s Kveller blog. Or maybe, in addition to being a mom, actor, scientist and activist, she has discovered one more hat to wear: fashion trendsetter.