What is Asthma in a nutshell?
- Narrowing and swelling of the airways
- Recurrent attacks of the bronchospasm
- Constriction of the muscles in the walls of the bronchi
What are bronchospasms often triggered by?
Allergic reaction - the immune system overreacts
What does the airway produce in relation to asthma?
Produced excess mucus which then further narrows the airways
What is the management for asthma?
- Bronchodilators - this opens the airway which relaxes smooth muscle
- Reduce inflammation by inhaled corticosteroids
What are the main causes of asthma?
Intrinsic - allergens, internal responses
Extrinsic - non-allergens, smoke, pollution
What happens to the airway in relation to intrinsic asthma?
Stimuli target hyper-responsive tissue leading to bronchoconstriction and inflammation
What are some examples of intrinsic asthma?
- Infection = viral infections which can lead to airway irritation and inflammation
- Drugs = like aspirin or nonsteroidal anti-inflammatory drugs can cause asthma attacks
- Stress = exacerbate asthma symptoms triggering inflammatory response
What is extrinsic asthma in relation to the immune system?
Exaggerated immune response - airway inflammation, bronchoconstriction, and increased mucus production
What are some examples of extrinsic asthma?
Pollen - trees, grass
Dust mites - microscopic dust mites
Pet dander - proteins found in the skin flakes, salvia, urine of pets
Mold spores - inhaling mold spore or damp enviroments
Food allergens
What is IgE?
Immunoglobulin E
What do IgE antibodies bind to?
IgE antibodies on the surface of mast cells bind to allergens, leading to mast cell deregulation
What does IgE do as an aintibody?
They are a type of antibody which help fights infections and are specifically involved in allergic reactions
What does the immune system do when it detects extrinsic asthma triggers?
- First exposure (sensitisation)
- Immune system mistakes it for being harmful
- Body produces the IgE antibodies which attach to mast cells and are now armed ready for exposure
When the IgE antibodies bind to the mast cells what happens?
- Re-exposure (allergic reaction)
- Causes mast cells to release histamine
- Triggers bronchoconstriction, mucus production, swelling
- Symptoms then occur
When antigen reacts with immunoglobulin, what does this cause?
- Histamine, kinins, prostaglandins and other mediators are released
- These then cause oedema, inflammation and increased mucus production
What does histamine cause?
- This chemical causes blood vessels to become leaky, leading to swelling
- Swelling and increased mucus production
What does Kinins cause?
- Causes blood vessels to widen (vasodilation) and the muscles around the airways to tighten (bronchoconstriction)
- Causes muscles around the airway to tighten
What does prostaglandins cause?
- Causes blood vessels to narrow (vasoconstriction) when can lead to low BP and reduce blood flow to the lungs
- Causes muscles around the airway to tighten
What nerve over stimulates and what happens to the airway?
- Vagus nerve overstimulates
- This causes a reflex due to excessive coughing = bronchoconstriction & bronchospasm
After overstimulation of the vagus nerve, what happens?
Air becomes trapped because of this and so forced expiration often causes bronchial collapse
When the residual volume increases what happens?
Increase in RV makes it difficult to cough so mucus cannot be expelled
Arrythmias and CNS depression can occur
What is Residual Volume?
Amount of air left in the lungs after exhalation
What is mucus plugging and atelectasis?
- Airway become completely obstructed by thick mucus plugs
- Leads to collapse of the lung tissue - a condition known as atelectasis
- Collapse of the lung air cannot enter or leave that area
When mucus plugging and atelectasis occurs, what happens?
Hypoxia is induced by airway constriction
