Respiratory Pre-Exam Preparation Questions

Respiratory Pre-Exam Preparation Questions 1. What is the mechanism of action of leukotriene-R antagonists (3 marks) Answer: • • • • • They act as antagonist for leukotriene binding on leukotriene receptors (CYsLT1) These prevents leukotrienes from binding on their receptors on mast cells and eosinophils This will cause decreased activation of PLC and thus decreased cleavage of PIP2 by PLC into IP3 and DAG and this decreased granulation of mast and eosinophils This less cytokine, histamine and other pro-inflammation substances being released via their granules This causes decreased narrowing of the airways 2. Describe the mechanism of action of cromoglycate and nedocromil (1 mark) Answer: These work by phosphorylating mass cells -> causing them to become stabilised -> degranulation -> decreased release of cytokines, prostaglandins and other pro-inflammatory mediators. 3. Describe how COPD may lead to: a. Lung inflammation b. Cor Pulmonale c. Why is there polycythaemia Answer a. In COPD, especially if the patient is a smoker there is cilia atrophy and goblet cell hyperplasia. This means that there is a decreased ciliary beat and thick mucus, so decreased mucus clearance. This will make it hard to clear pathogens, so pathogens will colonise and cause inflammation b. COPD somewhat decreases O2 entry into the alveoli -> less O2 diffusion from the alveoli into the alveolar capillary -> hypoxemia -> impaired gas exchange and the hypoxemia causes vasoconstriction -> this will cause blood to be to a place of lesser resistance -and a place where there is normal/okay gas exchange. If too much of this happens at many places we get pulmonary hypertension due to the vasoconstriction as this increases pressure and resistance. Since in the lung there is higher pressure in the lungs, this will make it harder for the right ventricle to pump blood in the pulmonary trunk, as higher pressure will be required to open the pulmonary valve. Due to this the right ventricles will need to generate higher pressure through higher contractility force. This means that the right ventricle will undergo hypertrophy. For a short while, this will be okay and will work, but however, after a while the right heart will fail, so there will be a right heart failure caused due to a pulmonary problem -> hence the CP c. This is because there is hypoxemia, which will be detected by the nephrons within the kidney -> they kidney will make EPO -> this will stimulate the bone marrow to make more red blood cells in attempt to carry and transport more oxygen 4. Briefly explain the mechanisms by which smoking causes: a. Pleasure (1 mark) b. Increases heart rate c. Increases breathing rate (1 mark) d. Increasing blood viscosity (1 mark) e. Increased risk of bleeding f. Endothelial injury Answer: a. Nicotine binds to nicotinic receptors causing the release of dopamine which goes to the nucleus accumbans -> rewards centre -> pleasure sensation b. Via binding to nACh-R -> PLC cleaves PIP2 into IP3 and DAG -> increased Ca2+ -> causing increased heart rate c. CO completes with O2 for Hb binding as they both have the exact same binding site on Hb and CO has more affinity than O2 by 250x -> oxygen cannot be carried to body tissues, as a result there is an increase in breathing rate in attempt to bring in more oxygen d. Again because of the competition between O2 and CO2 therefore there will be hypoxemia -> these is detected by the kidney -> EPO -> increased RBC’s production in attempt to increase the binding opportunities of O2 -> but this will also increase the thickness of the blood (viscosity) because of the increased number of red blood cells e. Smoking inhibits coagulation factors -> bleeding f. Smoking release oxygen reactive species -> endothelial injury 5. What are the FOUR defence mechanisms in the respiratory system Answer: a. b. c. d. Cilia beats to clear mucus that traps pathogens Resident macrophages Cough reflex IgA antibodies 6. Explain in detail the pathogenesis of central sleep apnoea Answer: • • This happens when there is an issue within the CNS such as a brain tumor, vagus, phrenic, intercostal or glossopharyngeal nerves do not work or taking opoid medications or a-fib or end stage kidney diseases This causes an episode during sleep where there is hypercapnia but hypoxemia. 7. What is the difference between allergy and atopy (1 mark) Answer: • • Allergy is an over exaggerated immune response to foreign particles - It involves both protective and hypersensitivity Atopy is an exaggerated IgE antibody in response to environmental antigens 8. Name the three cells’ types present in Th2 mediated immune response Answer: • • • B cells Eosinophils Mast cells