The respiratory center in the brain controls the muscles that are involved in breathing. The automatic signals from the brain control your breathing. Our body depends on a constant supply of oxygen to stay alive so breathing is very important.
The capillaries are small blood vessels where the gas exchange takes place. In the lungs the oxygen moves across the alveoli and capillaries to the blood where the oxygen is needed. Carbon dioxide passes from the blood into the alveoli. Inside the body tissue, oxygen from the blood passes to the tissues, while carbon dioxide moves into the blood.