When it comes to another gritty medical drama you'd be justified in thinking, "Do we need another one?" In the case of CBS's "Code Black", premiering tonight, we certainly do.

Based on the award-winning documentary by Ryan McGarry, "Code Black" follows the lives of a group of first year residents working at the Angels Memorial Hospital trauma center, one of the busiest in the nation.

Thanks to a continual influx of patients, the trauma center's resources are often overwhelmed by the sheer volume of patients, sending the center into "Code Black" – two words you really don't want to hear as a resident or patient.  

The cornerstone of the operation is Residency Director, Dr. Leanne Rorish (Marcia Gay Harden), a no-frills leader whose roar is often as bad as her bite.

On the surface this part looks like it was written specifically for Harden. Her portrayal is effortless, so its surprising to hear that doing a medical drama, especially something as fast paced and dialogue heavy as this, was the last thing she wanted.

"Years ago I did 'Chicago Hope' episode as a guest star, not in a doctor role," Harden told HNGN and a small group of reporters while promoting the show as the Television Critics Association Press Tour in July. "My first thought was no."

"I don't want to do a medical show, surrounded by 9,000 extras, in some high energy thing where you pretend with your hands, placing them in sticky blood. And then they say cut and you can't use your cell phone!

I said, "I don't think so," she ads.

That was until she watched the documentary the show is based and carefull read the script. "I could see a kind of generosity in the characters and the doctors and thought it's something I wanted to do," she reveals.

Thanks to an impressive ensemble cast that also includes Bonnie Somerville, Raza Jaffrey, Luis Guzmán, and Benjamin Hollingsworth viewers will be glad she did too and something co-star Hollingsworth attests to.

"Marcia is the best," he reveals to HNGN exclusively. "She has most of the technical jargon and is pro. But she's only scary on camera – about how talented she is. She' just a tour-de-force."   

"Code Black" premiers tonight 10PM/9c on CBS. For more with Marcia Gay Harden read on.

Why will people like this show more than some of the other medical shows?

The stories are universal and there are infinite possibilities for drama. For us, the problem isn't getting the stories, it's the way we tell them, not sentimental but authentic. It's a challenge.

What do you like about your role?

She's a really rich character. I'm a woman in my 50s and no one has to come to me to say play this fierce rich General. She's a General in some ways and that's fantastic.

Will we see more of your character's backstory?

We'll delve more into that because her backstory has created a certain attitude in life for her. I think of all the people I know and everyone has a backstory of some kind. There's more tragedy for some than for others, so it's created a certain way she has of working and maybe a certain shut down-ness. I'll say this because I'm divorced: divorce is a backstory and is its own tragedy for anyone who has been through it. It's not pretty and not easy. That creates ways that you can shut down, so I think each character has something they're really trying to move forward with that gets in the way of work, and that's when it's interesting. How do work and real life infiltrate?

So this is a game changer for you?

Well let's see – to God ears!

You make this part look effortless. Is it that easy? 

No, it really wasn't. It was hard work. The language is very hard because it doesn't mean anything to me. I have to learn what every single thing is so when I have a line like, "MVC with a positive PSI, unrestrained, push two amps of bicarb," I have to break it down: MVC is "motor vehicle collision"... PSI is "passenger-side intrusion," meaning the passenger side was hit. Unrestrained means "not wearing a seatbelt." I actually asked the writers if it'd possible to be unrestrained in the newer vehicles and they said it was. I even had to learn what bicarb did; otherwise I can't do it.

Are you better at the medical jargon now?

I'm telling you, if you need a thoracotomy, I can do it! [laughs] Someone's going to fall down at the airport and they're going to yell "Doctor!" and I'll lurch forward and have to remember we are in a nation that sues. And if I save a life and break a nail, I'll be sued. I'm going to have to remember, "Sorry buddy – S.A.G."

You got your SAG card from doing work as an extra. What do you remember about that time?

I was doing a Woody Allen film 100 years ago – my memory of it is that it got dark and we were sitting in a tent with no lights – this is in the day of dial phones, no cell phones. So the rules were that you needed a light and have a dial phone. I said to a grip, "There are no lights in here. We can't read." He put in some lights and I remember cockroaches running off the furniture. I was an extra for many years and the extra stories vary. We were background, and a number – not a person

Do you remember the movie?

I don't, I remember I also auditioned for the Oliver Stone film "Born On The Fourth of July" as an extra. That's how I got my union card.

Do you interact with the extras on the show now?

100%! They are actors, of course!

When you sign a seven-year contract, what are some of the things that need to be in place?

I signed a seven-year contract? Oh crap [Laughs]. My biggest concern is my children and being a good mom to them when my hours are so cuckoo. I have no control over that, other than to trust in the crew and the writers. I can say, "My family needs me." You know they gave me the morning off to take my little one to the first day of school, and they gave me time off to go to Napa so my daughter could start a semester at art school. I told them what was important to me, and I don't ask for time off for stupid stuff. It's also not just my story, every character has a good story and that's the hope – that everyone pops and you want to see them. I don't have to be there all the time.

This doesn't seem like a show where you have to deal with hours of hair and makeup?

I'm desperately upset about that too – I have to tell you [laughs]. But there's still at least an hour in hair and makeup. I feel we're obsessed youth and the sexuality of youth, and we forget that a woman in her 50's is also a sensual person. But in this case I don't get to do makeup and hair and glamour. The hair is in a ponytail, it's messy and I have no makeup. The camera is way down on the ground below me pointing at my chin, and that's what kills me. I'm like please – Dear God! – raise the camera. Mama will look tired.

What do you do to stay looking so lovely?

Lately I haven't been able to do anything because there's just no time. We're doing 15-hour days sometimes and there's just no time. In the morning I feel I should go on a jog, but by the time I potty the dog, get ready to go it's 5:30 in the morning and I have to leave. And not getting home until 10 o'clock – they're long days.

Do you look at doctors differently now?

Oh 100%! When we were shadowing the doctors no one yelled STAT, well nobody yelled. Nobody ran to the ambulances if there was an urgent call they would assess and figure out what they were doing. There's a beautiful scene in the documentary the show is based on where one of the doctors is walking and touching his head. Someone has just died and he's walking down the hall to a door that says something like Consult Room, and it's the family grief room. It's where he's going to announce tragic news. He goes in that door – slowly. The door shuts and the camera stays outside the door and you hear sobbing. The tenor and rhythm of that sound is known to all of us, and it was so subtle, yet beautiful. That's that doctor's job, once a day.