This is the first episode in which the opening voiceover contains the voices of all of the main characters.

Ratings: 22.5 million viewers; 14.2/21.0

Guest stars Loretta Devine (Adele Weber) and Jeffrey Dean Morgan (Denny Duquette) previously worked together as guest stars on the WB show Supernatural in the episode "Home".

This episode was aired as a two-part season finale special with "Losing My Religion".

This episode was voted #21 on the Futon Critic's 50 Best Episodes of 2006 article.

(opening voiceover)
Meredith: Human beings need a lot of things to feel alive.
George: Family.
Cristina: Love.
Izzie: Sex.
Derek: But we only need one thing ...
Webber: To actually be alive.
Cristina: We need a beating heart.
Addison: When our heart is threatened ...
Alex: We respond in one of two ways.
George: We either run or...
Izzie: We attack.
Webber: There's a scientific term for this:
Alex: Fight...
Addison: Or flight.
Bailey: It's instinct...
Meredith: We can't control it.
Izzie: Or can we?

Burke: Cristina.
Cristina: You don’t have to say anything. I know you’re sorry. And I know you didn’t mean to kick me off the transplant and I’m not mad. (pause) I mean I was but I’m not anymore. So don’t worry about it. Don’t even think about it, okay? I mean, all that matters is that you get better and we’ll get through this. I’m here for you, whatever you need. Anything.
Burke: Okay. I need you to--to check on Denny Duquette.
Cristina: Okay. That was my best supportive girlfriend and you kinda ruined it with medicine.

Bailey: Anything I can get for you Dr. Burke?
Burke: No, I'm fine.
Bailey: There, there must be something.
Burke: It would be nice to have some ice chips. And, uh, a touch of morphine if I'm allowed. And, uh, Cristina.
Bailey: Coming right up. (as she walks out of the room) Where is Cristina? Where are, where are all the little suck ups?
Burke: Excuse me?
Bailey: My interns. My ass-kissing, surgery-hungry, competitive suck-ups. Where are they? Why aren’t they here fetching you ice chips and morphine? Why aren't they here sucking up? You know something.
Burke: I'm a patient.
Bailey: Preston Xavier Burke, what have you done with my suck-ups?!

Adele: I was just tryin’ to remember the night that I lost my virginity and I can’t. I remember who I was with and I remember that I was 18. I can’t remember any of the details.
Addison: I can remember all of the details. Kinda wish I couldn’t.
Adele: That bad?
Addison: No. Just not good. Good came later. And then really good came.

Camille: It's okay Aunt Adele. I'm fine.
Adele: When your Uncle Richard finds out that you were cashin' in your V-Card none of us will be fine.

Izzie: Cristina can’t you just try to understand? I love him.
Cristina: You don’t even know him.
Izzie: I do know him.
Cristina: No. You never even seen him outside the four walls of this hospital. You don’t know him.
Izzie: I know him. And maybe I haven’t lived with him or work with him like you do with Burke. But I do know him. And there’s...there’s possibility here. And giving the choice of running or staying...
Cristina: You should run. A sane person, a person who values her career and everything she worked for, a person who values her own heart, for God’s sake, that person would run.
Denny: That sane person would marry me.
Izzie: What? What did you say? What did he say? (after commercial break) He said marry me? He said marry me, right?
George: He did.

Adele: How dare you send those kids away.
Richard: Adele. Please, you're emotional right now.
Adele: I just told my sister that her baby's cancer is back. You damn right I'm emotional. If you don't wanna bend your prescious rules for Camille, fine. Don't do it for her, do it for me. Do it for your wife who never asks you anything about your long hours. Who looks the other way when you have an affair with another woman. Who sobered you up when that woman left you. Who stayed with you when everyone---everyone said that I would be better off alone. I'm not asking you. I'm telling you. You're gonna make this up to Camille. You're gonna proritize the needs of your family above the needs of your other patients. Or you're gonna find a new place to sleep.

Episode Title: Deterioration of the Fight or Flight Response

The episode title comes from the 2002 song by The Flamming Lips of the same name.