Cherries stars locked themselves in the dressing room for half an hour after the demoralising defeat.
Cook said: “Words have been said, players have stepped up and spoken but it is no good unless we do it on the pitch.
“We are men in the dressing room but played like kids.
“These performances have been produced all year and something had to be said because it was embarrassing to concede four goals at home.
“It was an open discussion because we players need to step up and we are not doing that on the pitch.
“Maybe we are doing too much talking but we can only answer the questions that are being asked by the media and in-house you have to answer a few home truths.
“What was said will stay behind closed doors and we have to have a response."
Cook revealed the team will not give up and will treat all of their remaining games as a "cup final".
He continued: "We have got six cup finals left but don't look like a team fighting for our Premier League lives.
“We have been saying this for a long time but what we are producing is nowhere near good enough.
“Against Newcastle we looked so open as a team it was frightening. Every time we gave the ball away Newcastle looked like scoring.
“We never looked like scoring, conceded four and it could have been more.
“We need to demand more, accept where we are at and still believe we can stay in this league because if the belief that we can stay up disappears then we have no chance."