“Action!” the word is said quietly but emphatically, and the cast and crew on the set of “Masters of Sex” jump into motion. The man behind the video monitor is longtime actor Adam Arkin, and it’s clear he commands respect from the director’s chair. Sitting behind him are two of the show’s executive producers, Michelle Ashford and Sarah Timberman — and they’re taking a literal backseat to Arkin’s subtle direction of the show’s second-season finale, skedded to air Sept. 28.

“For a show like ‘Masters’ that is so performance-based, where there’s so much subtext and nuance involved, Adam makes for an ideal director,” explained Timberman. “As an actor himself, he thinks about material from the inside out, so I think the cast felt enormously comfortable in his hands.”

While still expanding his already lengthy resume with the occasional acting gig, Arkin’s been steadily building a formidable reputation as a go-to director for TV’s premier dramas. This season, he’s not only steering Showtime’s “Masters,” as well as FX’s “The Bridge” — he also recently helmed episodes of “The Blacklist,” “Justified” and “Sons of Anarchy.” He was a producing director on the first season of “The Americans.”

“As I started doing more and more acting on television, my desire to be pushed creatively needed an added element, and directing fit the bill,” he said. “I often joke about the fact that when other kids were being taken to baseball games and sporting events and fishing trips, my father was taking me to see silent Russian films.”

Arkin learned the craft by shadowing directors on the sets of shows he was working on — eventually convincing the producers of “A Year in the Life” to let him take the reins. That led to opportunities on other shows he was acting on (“Northern Exposure,” “Chicago Hope,” “Boston Legal”) — and opened the doors to regular work as a director.

FX has effectively made him an inhouse helmer. “It’s been a real creative home for me,” he said. “It’s not as if, (in general), all directors come in and do whatever they want. If it doesn’t feel like it’s tonally right for the show or you’ve missed the mark, you may not be back. But (FX) would rather (you try something different) than try to squelch every impulse and spontaneous idea.”

This season, Arkin serves as both actor (a DEA agent) and director on “The Bridge” and on “Masters” as a PR expert hired to present the groundbreaking work of Masters and Johnson to America.

Thanks to his crossover abilities, Arkin says other creatives figure he knows a secret way to speak to thesps. “The bad news I have to break to people is that there is no one way to talk to actors,” he said. “You need to suss out what works for a given actor’s method and psychology. And what one actor needs is exactly the last thing you want to say to another actor.”

Though Arkin is set to direct an episode of Rainn Wilson’s “Backstrom” for Fox, his need for a creative push has him looking for a change of genre. “When I started directing more regularly, a lot of people thought that comedy was going to be where I ended up,” he said, referring to his start on the kind of laffers his father, Alan, cut his teeth on. “I’ve ended up doing a plethora of really rough cable shows. It would be nice to break it up with a laugh or two.”

According to Timberman, that’s another role he plays on set: “Adam is a killer joke-teller,” she said, “even if his repertoire is of the Borscht Belt variety.”