Respiratory Pharmacology 1 Flashcards
where are cell bodies of the preganglionic fibres located?
Cell bodies of the preganglionic fibres are located in the brainstem.
Where are cell bodies of the postganglionic fibres located?
Cell bodies of postganglionic fibres are embedded in the walls of the bronchi and bronchioles.
what does stimulation of postganglionic cholinergic fibres cause?
Bronchial smooth muscle contraction mediated by M3 muscarinic ACh receptors on airway smooth muscle cells. It also causes increased mucus secretion mediated by M3 muscarinic ACh receptors on goblet cells.
What does stimulation of postganglionic noncholinergic fibres cause?
Stimulation of postganglionic noncholinergic fibres causes bronchial smooth muscle relaxation mediated by nitric oxide and vasoactive intestinal peptide (VIP).
Stimulation of the sympathetic division of the nervous system has what effect on bronchial smooth muscle? What is the transmitter?
Sympathetic stimulation causes bronchial smooth muscle relaxation via β2-adrenoceptors of airway smooth muscle cells. Transmitter is adrenaline released by the adrenal gland.
Stimulation of the sympathetic division of the nervous system has what effect on mucus secretion? What are its mediators?
Sympathetic stimulation by adrenaline decreases mucus secretion. Its mediators are β2-adrenoceptors of goblet cells.
Stimulation of the sympathetic division of the nervous system has what effect on mucociliary clearance? What are its mediators?
Sympathetic stimulation increases mucociliary clearance. Its mediators are β2-adrenoceptors of epithelial cells.
Stimulation of the sympathetic division of the nervous system has what effect on vascular smooth muscle? What are its mediators?
Sympathetic stimulation causes vascular smooth muscle contraction. Its mediators are α1-adrenoceptors of vascular smooth muscle cells.
How do actin and myosin filaments generate contraction of smooth muscle?
Actin and myosin filaments of muscle slide across each other to generate force- contraction.
What does MLCK stand for? What is its function?
MLCK is myosin light chain kinase. It phosphorylates dephosphorylated MLC.
How does smooth muscle contract?
Phosphorylation of MLC in the presence of elevated intracellular Ca2+ and ATP enables contraction of smooth muscle.
How does smooth muscle relax?
Dephosphorylation of MLC by myosin phosphatase causes smooth muscle relaxation.
What is the function of myosin phosphatase?
Myosin phosphatase dephosphorylates MLC to produce dephosphorylated MLC and enable smooth muscle relaxation.
Compare the rates of phosphorylation and dephosphorylation in the presence of elevated intracellular Ca2+.
In the presence of elevated intracellular Ca2+, the rate of phosphorylation exceeds the rate of dephosphorylation, resulting in increased contraction of smooth muscle.
How is the return of intracellular Ca2+ concentration to basal level achieved?
Primary and secondary transport.
Chronic asthma involves pathological changes to the bronchioles from long-standing inflammation, name them.
- Increased smooth muscle mass (hyperplasia and hypertrophy).
- Accumulation of interstitial fluid (oedema).
- Increased secretion of mucus.
- Epithelial damage (exposing sensory nerve endings).
- Sub-epithelial fibrosis.
What effect does airway narrowing by inflammation and bronchoconstriction have on airway resistance, FEV1 and PEFR?
Airway narrowing increases airway resistance, decreases FEV1 and decreases PEFR.
Bronchial hyper-responsiveness in asthma is due to what?
Epithelial damage, exposed sensory nerve endings, and increased airway sensitivity.
What do provocation tests involve and reveal?
Patient inhales bronchoconstrictors e.g. histamine or methacholine. The test reveals hyper-responsiveness.
What type of hypersensitivity reaction is the immediate phase of an asthma attack?
A type 1 hypersensitivity, consisting of early phase bronchospasm and acute inflammation. Involves mast cells and mononuclear cells, which release spasmogens, chemotaxins and chemokines.
What type of hypersensitivity reaction is the delayed phase of an asthma attack?
A type 4 hypersensitivity reaction, consisting of late phase bronchospasm and delayed inflammation. Also causes epithelial damage, airway hyper-responsiveness, wheeze, mucus hypersecretion and cough. Involves TH2 cells, monocytes, eosinophils.
What type of cells contribute to asthma in a nonatopic individual?
Phagocytes phagocytose the antigen presented by dendritic cells. There is a cell-mediation immune response involving IgG and macrophages. There is also a low-level TH1 response.
What type of cells contribute to asthma in an atopic individual?
In an atopic individual, in mild/moderate asthma, it is predominantly a TH2, antibody-mediated immune response involving IgE. In severe atopic asthma, TH1 also contributes.
How are eosinophils involved in the development of allergic asthma?
Eosinophils differentiate and activate in response to IL-5 released from TH2 cells.
How mast cells involved in the development of allergic asthma?
Mast cells in airway tissue express IgE receptors in response to IL-4 and IL-13 released from TH2 cells.
In the development of allergic asthma, crosslinking of IgE receptors stimulates what?
Calcium entry into mast cells and release of Ca2+ from intracellular stores causing the release of spasmogens, e.g. histamine and leukotrienes that cause airway smooth muscle contraction. They also cause release of prostaglandins, chemokines and chemotaxins attracting inflammation causing cells, e.g. monocytes and eosinophils.
What are the two broad categories of drugs used in the treatment of asthma?
Relievers and controllers/preventors.
What do relievers do in asthma? Name them.
Act as bronchodilators.
- Short acting β2-adrenoceptor agonists.
- Long acting β2-adrenoceptor agonists.
- CysLT1 receptor antagonists.
What do controllers/preventers do in asthma? Name them.
Controllers/preventors act as anti-inflammatory agents that reduce airway inflammation.
- Glucocorticoids.
- Cromoglicate.
- Humanised monoclonal IgE antibodies.
Explain mechanism of action of β2-adrenoceptor agonists.
Act as antagonists of smasmogens. They cause airway smooth muscle relaxation.
Explain mechanism of action of short acting β2-adrenoceptor agonists, their indication and an example.
SABAs, e.g. Salbutamol. First line in mild, intermittent asthma. Relievers. Act rapidly to relax bronchial smooth muscle, maximal effect within 30 minutes, and persists for 3-5 hours. They increase mucous clearance, and decrease mediator release from mast cells and monocytes.
Explain the mechanism of long acting β2-adrenoceptor agonists, their indication and an example.
E.g. salmeterol and formeterol, or combination inhalers (symbicort and seratide). They should be used in nocturnal asthma. Should never be used alone, but in combination with a glucocorticoid.
explain the mechanism of action of cysteinyl leukotriene (CysLT1)receptor antagonists.
CysLT1 receptor antagonists act as competitors at the CysLT1 receptor. CysLTs are derived from mast cells (inflammatory cells), and cause smooth muscle contraction, mucus secretion and oedema. CysLT1 receptor antagonists block these, relaxing bronchial smooth muscle.
Give an example of, and an indication for CysLT1 receptor antagonists.
E.g. montelukast, zafirlukast. Given orally.
They are used as an add-on therapy in bronchospasm of mild, persistent asthma.
They are also used in combination with e.g. ICS in more severe asthma. May cause headaches and GI upset.