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Bronchoconstriction is defined as the narrowing of the airways in the lungs (bronchi and bronchioles). Air flow in air passages can get restricted in three ways: [3] a spasmodic state of the smooth muscles in bronchi and bronchioles; an inflammation in the middle layers of the bronchi and bronchioles; excessive production of mucus.
Bronchospasm or a bronchial spasm is a sudden constriction of the muscles in the walls of the bronchioles. It is caused by the release (degranulation) of substances from mast cells or basophils under the influence of anaphylatoxins. It causes difficulty in breathing which ranges from mild to severe.
The parasympathetic reflex loop consists of afferent nerve endings which originate under the inner lining of the bronchus. Whenever these afferent nerve endings are stimulated (for example, by dust, cold air or fumes) impulses travel to the brain-stem vagal center, then down the vagal efferent pathway to again reach the bronchial small airways.
The parasympathetic nervous system decreases respiration and heart rate and increases digestion. Stimulation of the parasympathetic nervous system results in: Constriction of pupils; Decreased heart rate and blood pressure; Constriction of bronchial muscles; Stimulation of digestion and gastric emptying; Increased production of saliva and mucus
The airways have a tone baseline, and consequently a baseline level of contraction of their smooth musculature. Airway tone is a key determinant of lung function and the presence of respiratory symptoms in obstructive lung diseases such as asthma , where baseline airway tone is elevated. [ 2 ]
Bronchial hyperresponsiveness (or other combinations with airway or hyperreactivity, BH used as a general abbreviation) [1] is a state characterised by easily triggered bronchospasm (contraction of the bronchioles or small airways). Bronchial hyperresponsiveness can be assessed with a bronchial challenge test.
This rate can be altered, however, by nerves that work to either increase heart rate (sympathetic nerves) or decrease it (parasympathetic nerves), as the body's oxygen demands change. Ultimately, muscle contraction revolves around a charged atom (ion) , calcium (Ca 2+ ) , [ 3 ] which is responsible for converting the electrical energy of the ...
Hypoxic pulmonary vasoconstriction (HPV), also known as the Euler–Liljestrand mechanism, is a physiological phenomenon in which small pulmonary arteries constrict in the presence of alveolar hypoxia (low oxygen levels).