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Bronchoconstriction is the constriction of the airways in the lungs due to the tightening of surrounding smooth muscle, with consequent coughing, wheezing, and shortness of breath. ==Physiology== 1. Bronchoconstriction is due to an activation of parasympathetic nervous system. Postganglionic parasympathetic fibers will release acetylcholine (ACh) next to the Reissessen muscle, a smooth muscle layer surrounding the bronchi. These smooth muscle cells have M3 type muscarinic receptors on their membrane. The activation of these receptors by ACh will activate an intracellular Gq protein, that in turn will activate the PLC pathway, that will end in an increase of intracellular calcium concentrations and therefore contraction of the smooth muscle cell. The muscle contraction will cause the diameter of the bronchus to decrease, therefore increasing its resistance. 2. Bronchoconstriction (definition) is defined as the narrowing of the airways in the lungs (bronchi and bronchioles). Air flow in air passages can get restricted due to 3 factors: - a spasmodic state of the smooth muscles in bronchi and bronchioles - an inflammation of the airways - excessive production of mucus due to an allergic reaction or irritation caused by mechanical friction of air (due to shear stress), overcooling or drying of airways. Bronchoconstriction is common in people with respiratory problems, such as asthma, COPD, and cystic fibrosis. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「bronchoconstriction」の詳細全文を読む スポンサード リンク
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