Asthma Flashcards
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
Hypoxia which is induced by airway constriction, what happens do O2?
- Air cannot diffuse through areas of the lungs as they are blocked by mucus plugs
- O2 being transported in bloodstream through the lungs and this will lead to reduce O2 leading to hypoxia
What happens to the respiratory muscles during hypoxia?
- Resp. muscles like the diaphragm and intercostal muscles work harder
- Causes increased effort which leads to laboured breathing
What happens when the body cannot get enough O2 in relation to CO2
Body cannot move CO2 so this leads up to build up of CO2 in blood
What is respiratory acidosis?
CO2 dissolved in the blood and forms carbonic acid, lowering blood pH
What is metabolic acidosis in relation to cells?
- Switch to anaerobic respiration production lactic acid
- This further reduces blood pH and causes a dangerous imbalance
What is hypoxemia?
Abnormally low levels of O2 in the blood
What does hypoxemia trigger?
Triggers vasoconstriction in the pulmonary arteries
Why is there an increased workload on the right side of the heart?
As the right side of the heart pumps blood to the lungs - the right ventricle has to work harder to push blood through narrowed bessels
This is due to pulmonary vasoconstriction occurs due to hypoxemia
What can happen in severe cases of increased work load on the heart due to pulmonary vasoconstriction?
Due to increased pressure (pulmonary hypertension) this strains the right side of the heart and can lead to right heart failure as well as increased JVP
What are eosinophils?
Type of WBC that helps body fight off parasites and responds to allergens
In relation to asthma, what do eosinophils do?
- Asthma attack they are over-activated in response to allergens or irritants
- Cause airway narrowing and inflammation
What long-term damage does eosinophils cause?
Long-term swelling and can damage airways making asthma worse over time
What chemical mediators do eosinophils release and what do they do?
- Leukotrienes
- Powerful chemical that contributes to inflammatory response
What do Leukotrienes cause?
Causes bronchoconstriction, increase mucus production which lead to prolonged inflammation
What are Chemotactic Factors
Small molecules released by mast cells that act as a signal to attract other immune cells - WBC to the site of inflammation
What are cytokines?
Signalling proteins also released by cells
What are Cytokines crucial for?
Cell-to-cell communication and influence behaviour of immune cells
What do Cytokines help coordinate?
The immune response by activating, attracting and increase production of other WBC
What happens when mast cells are activated?
Mast cells are activated and release chemotactic factors and cytokines
Once chemotactic factors and cytokines are released, what do the chemicals signal?
- They signal eosinophils and neutrophils to move into inflamed area of lungs and airway
- Influx of other WBC intensifies the immune response which leads to more inflammation and further constriction of the airways
