When you breathe, you draw oxygen into your lungs and exhale carbon dioxide wastes. While you can exert some control on your breathing rate, the basic process is controlled automatically by your body. The mechanisms that regulate your breathing are processed in a portion of your brain called the respiratory control center.
Respiratory Control Center
Your respiratory control center sits at the bottom of your brain in an area called the medulla oblongata, which is part of your brain stem. The medulla oblongata connects directly to your spinal cord and contains two types of nerve cells collectively known as neurones. Your inward breaths are controlled by cells called inspiratory neurones, while your outward breaths fall under the control of your expiratory neurones. To perform their work and properly regulate your breathing patterns, your neurones depend on information received from several different areas in your body.
Chemoreceptors
An area of your brain stem near the medulla oblongata contains specialized sensors called the central chemoreceptors. These chemoreceptors sense changes in the pH levels of your cerebrospinal fluid, or CSF, which surrounds your spinal cord and brain. When the acidity of your CSF changes, your central chemoreceptors alert your respiratory control center. Additional sensing structures, called the peripheral arterial chemoreceptors, sit on your body's main blood vessel, the aorta, as well as on the main branch of your carotid arteries. These sensors detect changes in the relative oxygen and carbon dioxide content of your arterial blood, then pass that information along to the main control center.
Lungs and Cerebral Cortex
Certain involuntary aspects of your breathing are also controlled in your lungs, where specialized receptors respond to various forms of irritation by making you sneeze, hold your breath or cough. Another type of receptor, located in your lung tissues and chest wall, appears to respond to stretching movements inside your lungs. However, researchers don't know precisely how these sensors contribute to breathing control. When you consciously control aspects of your breathing, you activate a portion of your brain called the cerebral cortex, which contains your higher mental faculties. In addition to controlling your breathing rate, you can control the depth of each individual breath.
Considerations
Factors that can trigger the need for changes in your breathing rate include exercise and other forms of physical exertion, the quality of the air in your local environment and your emotional state. In addition, if fluid builds up in your lungs, specialized sensors in your lungs' air sacs can trigger the onset of shallow rapid breathing. Also, when you engage in physical activity, movement sensors in your joints and muscles may send additional breathing control signals to your respiratory control center.
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