We all know our brains control everything and that we can control certain functions ourselves.

What I'm curious about is can someone have so much control over their brains that they can control things like making the heart stop for a few seconds or control other organ functions that normally just happen? (liver, kidney...)

Those that practice forms of meditation and Zen Yoga and such believe they can. And biofeedback studies show that humans can slow down their heart-rate and lower blood pressure. In essence we all do that - think about when we're nervous at a doctor's office and we try to relax by picturing ourselves on a beach.

As for controlling a function to where it totally stops - I do not know. I don't think I would want to try that.

Many people use biofeedback to control their breathing when they have a panic attack. When their heart is racing, breathing techniques slow their heart rate and helps them to relax. (It works for me)