Physics Body Set Up how resolve it?

because when I activate the physique of the neck, the neck becomes soft? and then it falls down?
I need the neck to be rigid, the same way he was animated stopped, what should I be doing wrong?
Is this a Node for it? or is there any Node or other way to make the body rigid when physics is activated?
someone can help me?

here is an demonstration

Can someone help me give me a light or is it difficult?