using nodejs and angular at the same time (a hybrid single page app)?

I am new to Angular JS...and the single page web app idea. I am used to web forms that post data to a back-end server where the server can process it as needed (Oauth, db calls, etc). But in Angular it seems like the only way to do this is to use the $http service. Is this correct? This seems to be OK to me because instead of using server side pages you can set up your own API and then use Angular $http to handle things. However, it just seems like there might still be some benefits to using Angular for your web app but also making other parts of your app use a normal back-end setup (like Node JS)...is it considered bad practice to have half of the app's urls use Angular and the other half directly using Node JS. I am not sure if this is possible but I would imagine it is. My guess is all you need to do for this is to set your routes a certain way. What thoughts do people have on this?

October 21, 2015
I just discovered that the essence of this question is what the MEAN stack is all about. The mean stack uses ExpressJS to create the backend api that is used by the frontend AngularJS. For a good book about MEAN stack...to learn it, check out MEAN Web Development