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You are in: Home > Chest Information > Understanding Your Lungs > How Do You Breathe?

How Do You Breathe?

There are special cells in the brain, lungs and blood vessels that monitor the levels of oxygen and carbon dioxide in the blood.

They send messages to the respiratory centre in the brain stem. In turn the respiratory centre sends signals to the respiratory muscles so that the body's needs (for oxygen and carbon dioxide) are constantly being met. For example, you breath faster when you exercise or hurry.

The respiratory muscles consist of the diaphragm and the intercostal muscles:

• The diaphragm sits underneath your lungs, separating them from the rest of your abdomen. When you breathe in, the muscle contracts, i.e. shortens and flattens. This action pulls air into your lungs from the atmosphere and your lungs expand. As you breathe out, it relaxes and air moves from your lungs back out to the atmosphere and the lungs deflate. In relaxed breathing, this is a passive process and requires no effort.
• The intercostal muscles are found between each of the ribs, allowing your chest to expand outwards and contract inwards.

These muscles work together to create more space within your chest for your lungs to fill with air and empty again. This is possible because your lungs are actually attached to the inside of the chest wall by a covering called the pleura. It has two layers, separated by a thin layer of fluid, to allow smooth movement between your lung and chest wall as you breathe in and out.

Breathing is carried out without you having to consciously think about it. However, you can override the signals by conscious control, for example to cough, sneeze, sing or hold your breath.

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