Asthma Flashcards
How do allergens trigger a type 1 hypersensitivity reaction in asthma?
Allergens from environment detected by dendritic cells
DCs present this to Th2 cells (in mucosal layer of bronchial wall)
This produces IL4 and IL5 cytokines
IgE Ab production - Type 1 hypersensitivity reaction
What does IL4 cytokine do when activated?
produces IgE Abs → coat mast cells (in epithelial bronchial layer) and stimulate them to release granules which inflam mediators (eg histamines, leukotrienes, prostaglandins)
What does IL5 cytokine do when activated?
activates eosinophils → enhances immune response, releases further cytokines and leukotrines (inflam mediator)
- leukotriene binds to leukotriene receptors on bronchial smooth muscle cells → constriction
- leukotriene binds to receptors on mucus glands (submucosa) → mucus secretion
How do the chemical mediators released by lungs cause chronic lung damage?
after few hours: eosinophils release chemical mediators that damage lung endothelium
Over time these changes become irreversible oedema, scarring, fibrosis → thickening of epithelial basement membrane → reduced airway diameter
Name some allergens and irritants which could trigger asthma
Allergens such as:
Pollen
Mold
Animal dander
Insect parts
Some chemicals
Irritants such as:
Smoke
Dust
Gas or Diesel fumes
Chlorine
Difference between obstructive and restrictive lung disease?
obstructive: difficulty expiring air from lungs
restrictive: lung volume decreased, reduced intake of air
Main difference between asthma and COPD physiology?
Asthma: airway narrowing due to muscle spasm - REVERSIBLE
COPD: airway narrowing due to chronic inflammatory damage to airways - IRREVERSIBLE
Therapeutic effect of B2 agonist?
relax smooth muscle
Therapeutic effect of muscarinic antagonist?
prevent smooth muscle contraction
Difference between restrictive and obstructive lung disease?
Restrictive: lungs restricted from fully expanding, with less lung volume due to ↓ lung elasticity or caused by a problem related to the chest wall expansion
Obstructive: difficulty expelling air from lungs due to narrowing of the airways. too much air remains in lungs
What effects does leukotriene have when activated y IL-5?
- leukotriene binds to leukotriene receptors on bronchial smooth muscle cells → constriction
- leukotriene binds to receptors on mucus glands (submucosa) → mucus secretion
- increases vascular permeability in airways
- attracts more immune cells to area
the overall effect of bronchoconstriction and inflammation causes airway obstruction
What effect do prostaglandins have on smooth muscle cells?
similar to leukotrienes
they bind to receptors on SMCs (increase constriction) and mucus glands (inc mucus secretion)
increases vascular permeability in airways
attracts more immune cells to area
the overall effect of bronchoconstriction and inflammation causes airway obstruction
Symptoms of asthma and copd
cough
wheeze
sob (dyspnea)
chest tightness
