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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.
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.
M 3 receptors directly lead to airway smooth muscle contraction, i.e., an increase in airway tone, while M 2 receptors (also) expressed by airway neurons suppress the further release of acetylcholine in a negative feedback loop, wherein cholinergic parasympathetic signalling reduces further cholinergic parasympathetic signalling, which may ...
Parasympathetic action helps in digestion and absorption of food by increasing the activity of the intestinal musculature, increasing gastric secretion, and relaxing the pyloric sphincter. It is called the “rest and digest” division of the ANS. [24] The parasympathetic nervous system decreases respiration and heart rate and increases digestion.
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.
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 action ...
For example, the sympathetic nervous system can accelerate heart rate; widen bronchial passages; decrease motility (movement) of the large intestine; constrict blood vessels; increase peristalsis in the oesophagus; cause pupillary dilation, piloerection (goose bumps) and perspiration ; and raise blood pressure. One exception is with certain ...