L9 Flashcards
How does the parasympathetic nervous system control the airways?
Parasympathetic postganglionic neurons release acetylcholine, which binds to M3 muscarinic receptors on airway smooth muscle, causing bronchoconstriction.
What is the role of β2-adrenoceptors in the respiratory system?
Circulating adrenaline binds to β2-adrenoceptors, causing relaxation of airway smooth muscle and bronchodilation.
How do glucocorticoids help in treating asthma?
Glucocorticoids reduce inflammation by decreasing cytokine production, inhibiting eosinophil activation, and reducing immune cell activity. Example: Beclometasone.
What are xanthine drugs, and how do they act as bronchodilators?
Xanthines like theophylline inhibit phosphodiesterase (PDE), increasing cAMP levels, which relaxes airway smooth muscle.
What is the mechanism of action of muscarinic receptor antagonists like ipratropium?
Ipratropium blocks M3 muscarinic receptors, preventing acetylcholine-induced bronchoconstriction.
How do antitussive drugs like codeine work?
Codeine acts on the brainstem cough center to suppress cough reflexes.
What happens to particles of different sizes in the respiratory system?
Large particles (>5 μm) impact the nasal cavity or pharynx.
Medium particles (1–5 μm) settle in the bronchi or bronchioles.
Small particles (<1 μm) diffuse into the alveoli.
How do irritant gases like nitrogen dioxide affect the lungs?
Nitrogen dioxide increases fluid in the alveoli, causing inflammation and impaired gas exchange.
What is byssinosis, and what causes it?
Byssinosis (“brown lung”) results from exposure to cotton dust in textile mills, potentially due to microorganisms or irritants on the dust.
How does asbestos exposure lead to mesothelioma?
Asbestos fibers cause chronic inflammation and damage, leading to mesothelial cell mutations and lung cancer.
Explain the mechanisms of asthma and how bronchodilators treat the condition.
Asthma involves bronchial hyperactivity, often triggered by allergens, which activate TH2 lymphocytes, causing bronchoconstriction and mucus secretion. Bronchodilators include:
- β2-agonists (e.g., salbutamol): Relax airway smooth muscle by increasing cAMP.
- Xanthines (e.g., theophylline): Inhibit PDE, raising cAMP levels.
- Muscarinic antagonists (e.g., ipratropium): Block M3 receptors to prevent acetylcholine-induced constriction.
Discuss the deposition of toxicants in the respiratory system based on their size and solubility.
Water-soluble gases dissolve in the mucus of the upper airways (e.g., sulfur dioxide).
Less soluble gases penetrate deeper, affecting the lower airways (e.g., nitrogen dioxide).
Particles:
- Large particles (>5 μm) impact nasal or pharyngeal walls.
- Medium particles (1–5 μm) settle in bronchi or bronchioles.
- Small particles (<1 μm) diffuse into alveoli, potentially causing fibrosis or alveolar damage.
What are the mechanisms and examples of respiratory toxicants causing lung damage?
Respiratory toxicants cause:
Bronchoconstriction: Direct stimulation of smooth muscle or irritant receptors (e.g., sulfur dioxide).
Inflammation: Increased permeability and immune cell infiltration (e.g., nitrogen dioxide).
Fibrosis: Repeated macrophage activation and fibroblast recruitment (e.g., crystalline silica in pneumoconiosis).
Lung cancer: Carcinogens like asbestos and cigarette smoke damage DNA, leading to mutations.
Compare and contrast the roles of glucocorticoids and β2-agonists in asthma management.
Glucocorticoids (e.g., beclometasone) reduce inflammation by inhibiting cytokine production and eosinophil activation. They are used for long-term control.
β2-agonists (e.g., salbutamol) relax smooth muscle by increasing cAMP and provide short-term relief from bronchoconstriction. Long-acting β2-agonists (e.g., salmeterol) are used for maintenance.
Describe the respiratory conditions caused by occupational exposure to toxicants and their mechanisms.
Byssinosis: Caused by cotton dust, leading to an allergic response or irritation.
Hypersensitivity pneumonitis: Triggered by organic particles (e.g., moldy hay), causing immune-mediated inflammation.
Fibrosis: Chronic irritation (e.g., silica exposure) activates macrophages, recruiting fibroblasts that deposit collagen.
Mesothelioma: Asbestos fibers cause chronic inflammation, leading to cancer of the pleura.
