A book called the hypnotic world of Paul McKenna goes into this kind of thing in great depth; I found it a great read.
Paul's words, the sub conscious mind is like a dark room full of objects, the conscious mind is like a flash light inside the sub conscious and whatever it shines upon is what you see, all your constant habits i.e. heart beet, blinking and breathing as Goldie said have a small light of there own and remain constantly present.
But go un-noticed by the conscious mind.