Drugs Affecting Airway Structure & Function Flashcards
What are some of the cellular processes underlying asthma?
Mucus hypersecretion, vasodilation, oedema, epithelial shedding, nerve activation, subepithelial fibrosis, bronchoconstriction
What contributes to airway constriction in asthma?
bronchoconstriction, mucus plug, oedema
Which part of airway constriction do preventer drugs help?
bronchoconstriction, mucus plug and oedema
Which part of airway constriction to relievers and controllers help?
Just bronchoconstriction
What holds airways open?
Smooth muscle, cartilage, attachments to parenchymal tissue, deep inspiration
What determines how fast and how much shortening of smooth muscle occurs?
The load on the muscle
What is the contractile mechanism of airway smooth muscle?
Increase in intracellular calcium, calcium binds to calmodulin, calmodulin activates myosin light chain kinase, myosin light chain phosphorylated, actomyosin ATPase activated, cross bridges between actin and myosin break and reform, results in cell shortening
What cause the increase in intracellular calcium?
voltage operated calcium channels and phospholipase C and inositol triphosphate releasing calcium from intracellular stores
What causes a decrease in intracellular calcium?
plasma calcium ATPases and sarcoplasmic reticulum calcium ATPases
What is the mechanism of regulation airway smooth muscle?
protein kinase A activates myosin light chain phosphatase. MLC phosphatase dephosphorylates myosin light chain. This prevents actin and myosin sliding and prevents contraction.
What is the action of PKC and Rho kinase?
Inhibit MLC phosphatase - this results in the smooth muscle being more sensitive to calcium and thus more able to contract
Which mediators result in smooth muscle contraction?
acetylcholine, histamine, leukotriene C4 and D4
Which mediators result in smooth muscle relaxation?
prostaglandin E2 and I2, adrenaline
What causes basement membrane thickening in asthma?
chronic epithelial cell damage where the repair process is not proportionate to degree of injury which leads to residual scarring
What are reliever drugs for asthma?
Short acting beta agonists