What Should I Expect When I'm In A ICU?

I'm getting surgery in a few days and I'm super nervous. I'm going to be in an intensive care unit and I just wanted to know everything that goes on while I'm there. I'm going to have a catheter ( which I'm freaked out about ) but what happens if I have to poop?! Am I going to have nurses around me 24/7? I'm just really scared and have no idea of what to expect.