Topic Resources Breathing is usually automatic, controlled subconsciously by the respiratory center at the base of the brain. Breathing continues during sleep and usually even when a person is unconscious. People can also control their breathing when they wish, for example during speech, singing, or voluntary breath holding.
Sensory organs in the brain and in the aorta and carotid arteries monitor the blood and sense oxygen and carbon dioxide levels. Normally, an increased concentration of carbon dioxide is the strongest stimulus to breathe more deeply and more frequently. Conversely, when the carbon dioxide concentration in the blood is low, the brain decreases the frequency and depth of breaths. During breathing at rest, the average adult inhales and exhales about 15 times a minute. The
lungs have no skeletal muscles of their own. The work of breathing is done by the diaphragm, the muscles between the ribs (intercostal muscles), the muscles in the neck, and the abdominal muscles. The diaphragm, a dome-shaped sheet of muscle that separates the chest cavity from the abdomen, is the most important muscle used for breathing in (called inhalation or inspiration). The diaphragm is attached to the base of the sternum, the lower parts of the rib cage, and the spine. As
the diaphragm contracts, it increases the length and diameter of the chest cavity and thus expands the lungs. The intercostal muscles help move the rib cage and thus assist in breathing. The process of breathing out (called exhalation or expiration) is usually passive when a person is not exercising. The elasticity of the lungs and chest wall, which are actively stretched during inhalation, causes them to return to their resting shape and to expel air out of the lungs when inspiratory
muscles are relaxed. Therefore, when a person is at rest, no effort is needed to breathe out. During vigorous exercise, however, a number of muscles participate in exhalation. The abdominal muscles are the most important of these. Abdominal muscles contract, raise abdominal pressure, and push a relaxed diaphragm against the lungs, causing air to be pushed out. The muscles used in breathing can contract only if the nerves connecting them to the brain are intact. In some neck and back
injuries, the spinal cord can be severed
Injuries of the Spinal Cord and Vertebrae Most spinal cord injuries result from motor vehicle crashes, falls, assaults, and sports injuries. Symptoms, such as loss of sensation, loss of muscle strength, and loss of bowel, bladder, and... read more
Diaphragm’s Role in BreathingWhen the diaphragm contracts and moves lower, the chest cavity enlarges, reducing the pressure inside the lungs. To equalize the pressure, air enters the lungs. When the diaphragm relaxes and moves back up, the elasticity of the lungs and chest wall pushes air out of the lungs. CLICK HERE FOR THE PROFESSIONAL VERSION  Copyright © 2022 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved.
What causes air to move into the lungs during inspiration?When the lungs inhale, the diaphragm contracts and pulls downward. At the same time, the muscles between the ribs contract and pull upward. This increases the size of the thoracic cavity and decreases the pressure inside. As a result, air rushes in and fills the lungs.
Which muscle helps the lungs take in air inspiration?Overview. The diaphragm, located below the lungs, is the major muscle of respiration. It is a large, dome-shaped muscle that contracts rhythmically and continually, and most of the time, involuntarily. Upon inhalation, the diaphragm contracts and flattens and the chest cavity enlarges.
What muscle action occurs during inspiration?Action: diaphragm is the main inspiratory muscle, during inspiration it contracts and moves in an inferior direction that increases the vertical diameter of the thoracic cavity and produces lung expansion, in turn, the air is drawn in.
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