Asthma Flashcards
What is asthma?
Chronic inflammatory disorder of the airways. Usually associated with:
- variable airflow obstruction
- increase in airway response to a varitey of stimuli
obstruction is often reversible
What are the two lung functions tests to diagnose asthma?
PEFR = peak expiratory flow rate FEV1 = forces expiratory volume in one second
How does ACh acting on M3 receptor cause bronchoconstriction?
M3 receptor is Gq coupled - activates PLC, IP3
Leads to raised Ca2+ levels.
Causes phosphorylation of MLC via MLCKinase
Results in contraction
Why are muscarinic antagonists not commonly used in asthma?
Loss of negative feedback may lead to enhanced airway contraction.
How do B adrenoreceptor agonists work?
Leads to increased cAMP.
Increased activity of PKA
- this inactivated MLCK
- leads to Ca sequesteration (get less constriction)
What is theophylline?
Phosphodiesterase inhibitor inhibitor
How does theophylline reduce bronchoconstriction?
Inhibits PDE. PDE is responsible for the break down cAMP. cAMP leads to PKA activation –> bronchodilation.
How are TH2 cells involved in IgE hypersensitivity reactions?
TH2 cells produce cytokines IL-13 AND IL-4 Activates B cells production of IgE antibody Acts on FCR1 located on mast cells- degranulation
What factors favour the TH1 ‘protective immunity ‘ phenotype to allergies?
Presence of older siblings
Early exposure to day care
TB, measles, Hep A
Rural environment
What factors favour the development of TH2 ‘allergic diseases’ phenotype?
Western use of antibiotics Western lifestyle Urban environment Diet Sensitisation to house mites
What are disodium cromoglycate and neclocromil and their MOA?
Cromones - mast cell stabilisers. Inhibitor mediator release from lung mast cells
How does Omalizumab work?
Binds Fc portion of IgE, prevents IgE binding to mast cells
