As a field expert in respiratory physiology, I can explain the process of how the body knows when to breathe. The respiratory system is regulated by a group of neurons known as the respiratory control center, which is located in the medulla oblongata, a part of the brainstem. This center is responsible for the automatic and involuntary control of breathing. The respiratory control center receives input from various sources. One of the key inputs is the level of carbon dioxide (CO2) in the blood. When CO2 levels rise, it triggers the respiratory control center to increase the rate and depth of breathing to expel the excess CO2. Additionally, the level of oxygen (O2) in the blood and the pH of the blood can also influence the respiratory control center. Moreover, there are chemoreceptors located outside the brain that can detect changes in the blood's CO2, O2, and pH levels. These chemoreceptors send signals to the respiratory control center, which then adjusts the rate and depth of breathing accordingly. The respiratory control center sends signals through the phrenic and spinal nerves to the diaphragm and intercostal muscles, which are the primary muscles involved in breathing. When these muscles contract, they create a negative pressure within the chest cavity, drawing air into the lungs. When they relax, the chest cavity returns to its normal volume, and air is expelled from the lungs. read more >>

A respiratory control center at the base of your brain controls your breathing. This center sends ongoing signals down your spine and to the muscles involved in breathing. These signals ensure your breathing muscles contract (tighten) and relax regularly.read more >>