Bronchial smooth-muscle tone

Bronchial smooth muscle tone. Changes in bronchial smooth muscle tone are particularly important in the bronchioles compared to the bronchi. Recall that the walls of the bronchioles consist almost entirely of smooth muscle. Contraction and relaxation of this muscle has a marked effect on the internal radius of the airway. An increase in bronchial smooth muscle tone, or bron-choconstriction, narrows the lumen of the airway and increases resistance to... 

Pulmonary disease Pilocarpine has been reported to increase airway resistance, bronchial smooth muscle tone, and bronchial secretions. Administer with caution and under close medical supervision in patients with controlled asthma, chronic bronchitis, or chronic obstructive pulmonary disease. 

Since the introduction of propranolol, it has been recognized that patients with bronchial asthma treated with beta-adrenoceptor antagonists can develop severe airways obstruction (84), which can be fatal (85) or near fatal (86,87) this has even followed the use of eye-drops containing timolol (88). Beta-blockers upset the balance of bronchial smooth muscle tone by blocking the bronchial beta2-adrenoceptors responsible for bronchodilata-tion. They also promote degranulation of mast cells and depress central responsiveness to carbon dioxide (89,90). 

Asthma, Chronic obstructive pulmonary disease P2-Agonists Reduce bronchial smooth muscle tone Formeterol, Salbutamol, Salmeterol, Terbutaline... 

CYP2J subfamily. CYP2J2 is the only gene of this subfamily. It is known to be expressed in many extrahepatic tissues and may play a role in the oxidative bioactivation of arachidonic acid to form epoxyeicosatrienoic acids, which modulate bronchial smooth muscle tone and airway transepithelial ion transport [53], CYP2J2 is also active toward other compounds such as linoleic acid and testosterone. Recently, it has been reported that CYP2J2 is involved in the intestinal first-pass metabolism of an antihistamine drug, astemizole [54],... 

Asthma symptoms are caused by bronchoconstriction and inflammation, and approaches to treatment are directed at both these physiological problems. Therefore, drugs that affect adrenergic/cholinergic bronchial smooth muscle tone and drugs that inhibit the inflammatory process are used to treat and control asthma symptoms. In the normal lung, bronchiole smooth... 

As discussed previously (Sec. II.B), bronchial smooth muscle tone is under autonomic control. Cold air and stimulation of receptors by irritants such as cigarette smoke, dust particles, and sulfur dioxide can also cause increased tone and hence bronchoconstriction (229). Bronchomotor tone is also modulated by vagal stretch reflexes and varies inversely with lung volume. Paradoxically, the rise in bronchomotor tone and/or increase in FRC during an attack of asthma may partially reverse the reduction in airway caliber that occurs in this condition, making assessment of response to therapy complex. Similarly, bronchodilators have been shown to cause paradoxical reductions in airflow and desaturation in some infants with history of wheeze, a phenomenon that has been attributed at least partially to changes in airway wall compliance (230-232). 

Cromolyn sodium (disodium cromoglycate) and nedocromil sodium are stable but extremely insoluble salts (see structures below). When used as aerosols (by nebulizer or metered-dose inhaler), they effectively inhibit both antigen- and exercise-induced asthma, and chronic use (four times daily) slightly reduces the overall level of bronchial reactivity. However, these drugs have no effect on airway smooth muscle tone and are ineffective in reversing asthmatic bronchospasm they are only of value when taken prophylactically. 

On contact with moist membranes, S02 forms sulfurous acid, which is responsible for its severe irritant effects on the eyes, mucous membranes, and skin. Approximately 90% of inhaled S02 is absorbed in the upper respiratory tract, the site of its principal effect. The inhalation of S02 causes bronchial constriction parasympathetic reflexes and altered smooth muscle tone appear to be involved. Exposure to 5 ppm S02 for 10 minutes leads to increased resistance to airflow in most humans. Exposures of 5-10 ppm are reported to cause severe bronchospasm 10-20% of the healthy young adult population is estimated to be reactive to even lower concentrations. The phenomenon of adaptation to irritating concentrations has been reported in workers. However, current studies have not confirmed this phenomenon. Asthmatic individuals are especially sensitive to S02. 

Smooth Muscle Local anesthetics depress contractions in gastrointestinal (Gl), vascular, and bronchial smooth muscle, although low concentrations initially may produce contraction. Spinal and epidural anesthesia, as well as instillation of local anesthetics into the peritoneal cavity, cause sympathetic nervous system paralysis, which can result in increased tone of Gl musculature see below). Local anesthetics seldom depress uterine contractions directly during intrapartum regional anesthesia. 

Anticholinergic agents may represent the first true broncho-dilators for the CB patients. Ipratropium by inhalation has been demonstrated to provide 5-6 hours of bronchodilation in CB as was similarly seen earlier with atropine (13). The mechanism of action is thought to be a blocking of the vagal efferent discharge which is responsible for the increased bronchomotor tone of the bronchial smooth muscle in CB as well as in CBA. Parenteral or inhaled atropine appears to have the deleterious effect of drying bronchial secretions and has not been useful for protracted therapy, whereas inhaled ipratropium does not appear to have this unwanted effect. 

Smooth muscle is relaxed. In the gastrointestinal tract there is reduction of tone and peristalsis. Muscle spasm of the intestinal tract induced by morphine is reduced, but such spasm in the biliary tract is not significantly affected. Atropine relaxes bronchial muscle, an effect that is useful in some asthmatics. Micturition is slowed and urinary retention may be induced especially when there is pre-existing prostatic enlargement. 

Isoproterenol relaxes almost all varieties of smooth muscle when the tone is high, an action that is most pronounced on bronchial and GI smooth muscle. Isoproterenol s effect in asthma may be... 

Documented effects The alkaloids convolvine and convolamine have anesthetic properties, produce irritation of the mucous membranes of the eyes, and large doses can paralyze the central nervous system. Due to high toxicity they are not used in medical practice. Their derivatives, convocaine and tropacin, were developed as preparations for medical use. Tropacin is used to treat Parkinson s disease, spastic paresis and other diseases following muscle tone increase. Tropacin is also recommended to treat ulcers, bronchial asthma, other cases of spasms of the smooth muscular system, and poisoning with phosphorganic compounds (Mashkovskii 1953 Khalmatov et al. 1984 Khodzhimatov 1989). 

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