In order to better understand the process of respiration, it is important to have a clear grasp on the components behind the process of respiration. There are many different components that affect the respiratory cycle, or, one complete inspiration (inhalation) and expiration (exhalation).
Muscles of respiration
The lungs are incapable of breathing in and of themselves and rely on the muscles that assist in breathing, such as the smooth muscle located in the bronchi, as well as the muscles of the diaphragm. The diaphragm is the primary muscle involved in respiration and is responsible for the rhythmic increasing and decreasing of pressure within the lungs. The pressure located within the chest and within the stomach are directly related to one another; as one rises the other decreases and vice verse.
During intense breathing, such as breathing during high levels of physical activity, other muscles become involved, such as the intercostal muscles which are responsible for the repeated outward and upward movment of the lower ribs. Additionally, the scalene muscles, pectoralis muscles and sternocleidomastoid muscles contribute to respiration by moving the ribs and other structures within the thorax.
Neurological control of respiration
Unlike the heart, the lungs cannot continue to breathe is nerves to the lungs have been severed. The lungs, in fact, are controlled by two portions of the brain; one responsible for the unconscious act of breathing and the other is responsible for the conscious act of breathing. The involuntary act of breathing is control by three centers located within the brain; the ventral respiratory group, the dorsal respiratory group and the pontine respiratory group. Conscious breathing, however, is controlled by the motor cortex located within the frontal lobe.
References
Saladin, Kenneth S.. Anatomy & physiology: the unity of form and function. 5th ed. New York: McGraw-Hill, 2010. Print.
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