Muscle, bronchial smooth

Nasal vasculature may offer some insight into this question, though research to date has been equivocal. Nasal turbinate vessels can be classified as either capacitance vessels or resistive vessels. Capacitance vessels appear to vasodilate in response to infection while resistance vessels appear to respond to cold stimuli by vasoconstriction. Buccal vascular structures also respond to thermal stimuli but appear to respond principally to cutaneous stimuli. How pharyngeal and tracheobronchial submucosal vessels react to thermal stimuli is not known, though cold-induced asthma is believed to result from broncho-spasms caused by susceptible bronchial smooth muscle responding to exposure to cold dry air.- This asthmatic response suggests an inadequate vascular response to surface cooling. 

The action of epinephrine and related agents forms the basis of therapeutic control of smooth muscle contraction. Breathing disorders, including asthma and various allergies, can result from excessive contraction of bronchial smooth muscle tissue. Treatment with epinephrine, whether by tablets or aerosol inhalation, inhibits MLCK and relaxes bronchial muscle tissue. More specific bronchodilators, such as albuterol (see figure), act more selec-... 

Expression (Human) Tissues Leukocytes, thymus, spleen, liver, ovary Cells PBLs, neutrophils,T-cells, dendritic cells, mast cells, eosinophils, macrophages, leukocytes Tissues spleen, small intestine, placenta, lung smooth muscle, Cells bronchial smooth muscle, CD34+ hemapoietic progenitor cells, monocytes, macrophages, mast cells, eosinophils, neutrophils, PBLs, human umbilical vein endothelial cells Tissues, heart, skeletal muscle, spleen, brain, lymp node, adrenal medulla, lung, human pumonary/ saphenous vein Cells monocytes, macrophages, mast cells, eosinophils, cardiac muscle, coronary artery, PBLs... 

Peripheral Gl, vascular and bronchial smooth muscle, vascular endothelium, platelets Peripheral Smooth muscle of ileum, stomach fundus (rat), uterus, vasculature, endothelium Peripheral None identified Peripheral Post-ganglionic sympathetic neurons, sensory neurons Peripheral Cardiac muscle, post-ganglionic parasympathetic neurons (myenteric plexus), esophageal and vascular smooth muscle... 

P2 Peripheral blood vessels Bronchial smooth muscles... 

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... 

Selective sympathomimetics cause relaxation of bronchial smooth muscle and bronchodilation by stimulating the enzyme adenyl cyclase to increase the formation of cyclic adenosine monophosphate. They may also improve mucociliary clearance. 

Some agents are bifunctional, causing the release of histamine and recruiting leukocytes. Bifunctional mediators include bacterial peptides, endotoxins, DNA, C3a, C5a and bradykinin. Each of these substances can exert dual effects. This may either occur directly, as in the case of bacterial peptides and bradykinin causing chemotaxis and bronchial smooth muscle contraction, or indirectly, as endotoxin and DNA conversion of complement. C3a and C5a act indirectly as complement fragments to effect histamine release, which in turn contracts bronchial smooth muscle. However, both appear to act directly to effect chemotaxis with C5a, the more potent fragment. 

These compounds competitively inhibit phosphodiesterase, resulting in an increase in cyclic AMP (see Box 14.3) and subsequent release of adrenaline. This leads to the major effects a stimulation of the central nervous system (CNS), a relaxation of bronchial smooth muscle, and induction of diuresis. These effects vary in the three compounds. Caffeine is the best CNS stimulant, and has weak diuretic action. Theobromine has little stimulant action, but has more diuretic activity and also muscle relaxant properties. Theophylline also has low stimulant action and is an effective diuretic, but it relaxes smooth muscle better than caffeine or theobromine. 

Inhalation in the form of an aerosol (p. 12), a gas, or a mist permits drugs to be applied to the bronchial mucosa and, to a lesser extent, to the alveolar membranes. This route is chosen for drugs intended to affect bronchial smooth muscle or the consistency of bronchial mucus. Furthermore, gaseous or volatile agents can be administered by inhalation with the goal of alveolar absorption and systemic effects (e.g inhalational anesthetics, p. 218). Aerosols are formed when a drug solution or micron-ized powder is converted into a mist or dust, respectively. 

IgE-mediated allergic reactions (p. 72) involve mast cell release of histamine (p. 114) and production of other mediators (such as leukotrienes, p. 196). Resultant responses include relaxation of vascular smooth muscle, as evidenced locally by vasodilation (e.g., conjunctival congestion) or systemically by hypotension (as in anaphylactic shock) enhanced capillary permeability with transudation of fluid into tissues— swelling of conjunctiva and mucous membranes of the upper airways ( hay fever ), cutaneous wheal formation contraction of bronchial smooth muscle-bronchial asthma stimulation of intestinal smooth musde—diarrhea. 

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. 

Methylxanthines have a number of other effects, including effects on smooth muscles and the cardiovascular system. The most notable effect on smooth muscles is relaxing the bronchi of the lungs. Theophylline is prescribed to treat mild forms of asthma. While both caffeine and theophylline will relax the bronchial smooth muscles, theophylline is used therapeutically because of its longer half-life. This allows the drug to stay in the therapeutic range longer. 

Due to its ability to stimulate relaxation of bronchial smooth muscle, theophylline is useful for treating the bronchoconstriction of asthma. 

Their actions on smooth muscle, in particular, can be complex. For example, both PGEs and PGFs induce contraction of uterine and gastrointestinal smooth muscle. On the other hand, PGEs stimulate dilation of vascular and bronchial smooth muscle, whereas PGFs induce constriction of these muscle types. 

The tti-adrenoceptors are located at postjunctional (postsynaptic) sites on tissues iimervated by adrenergic neurons. a2-Adrenoceptors having a presynaptic (i.e., neuronal) location are involved in the feedback inhibition of norepinephrine release from nerve terminals (discussed later). a2-Receptors also can occur postjunc-tionally. The (3i-adrenoceptors are found chiefly in the heart and adipose tissue, while (32-adrenoceptors are located in a number of sites, including bronchial smooth muscle and skeletal muscle blood vessels, and are associated with smooth muscle relaxation. 

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