Your Brains Core Function Control: How does it keep you going?

We generally do not think a lot about breathing, digesting, our heart running or other “automatic” things unless we are having trouble with them. How does the brain pull that off? We also do not typically “think” to create hormonal control. How does the brain pull that off? How can all this automatic operation of the wonderful organ our brain is be affected by things such as conscious thought, learning, stress and meditation?