Breathing, reflexes and other involuntary functions of the body are primarily governed by the brainstem. This is the region of the brain located at the back of the head that connects the brain and spinal column. The brainstem has several substructures that control different functions of the body.
In humans, the brainstem is divided into the medulla oblongata, pons and midbrain. The medulla oblongota is the lowest part of the brainstem, located next to the top of the spinal column. It controls breathing and other essential functions, such as blood pressure. Reflexes are controlled by the midbrain, causing activity in the same area that pain receptors are located in.