pathophysiology of respiratory diseases (asthma)

Question 1

what is asthma ?

Answer 1

chronic inflammatory condition typically categorised by episodes of reversible airflow limitation and bronchial hyperresponsiveness, where the patient experiences difficulty breathing (dyspnoea).

Question 2

what are the 2 components of the pathophysiology ?

Answer 2

(1) An inflammatory/immune system component, in which the individual develops a hypersensitivity to a specific stimulus (typically an allergen such as pollen or house dust mites), causing an inflammatory response upon subsequent exposures to that stimulus.

(2) An airway component, where the allergen-induced inflammation release mediators that affect cellular function, produce limitations in tissue function (i.e. airflow), resulting in the generation of symptoms (dyspnoea, excess mucus, and cough).

Question 3

how does a healthy airway look compared to an asthmatic airway ?

Answer 3

Question 4

what are the 2 stages of allergic asthma ?

Answer 4

(1) Sensitisation - where the immune system first encounters the allergen and develops an adaptive (antibody- and lymphocyte-mediated) immune response.

(2) The allergic response – where the allergen is subsequently re-encountered, triggering the adaptive response previous primed during sensitisation. This generates an inflammatory response within the airways, producing symptoms.

Question 5

describe sensitization

Answer 5

• Allergen enters the body – It is inhaled and reaches the airway.
• Immune cells detect the allergen – A special immune cell (Antigen-Presenting Cell or APC) captures and processes the allergen.
• T cells get activated – The APC presents the allergen to a naïve helper T cell, which then matures into a Th2 cell.
• B cells produce antibodies – The Th2 cell interacts with a B cell and signals it (using IL-4) to produce IgE antibodies.
• IgE binds to mast cells – The IgE antibodies attach to mast cells, which are responsible for allergic reactions.
• Eosinophils are activated – Another signal (IL-5) triggers eosinophils, which are white blood cells involved in allergic inflammation.
• Allergic response occurs – When the person is exposed to the allergen again, mast cells release histamine, leading to allergy symptoms like sneezing, itching, and swelling.

Question 6

describe the allergic response

Answer 6

• Allergen exposure – Allergens (like pollen or dust) enter the nose and airways.
• Mast cells release inflammatory chemicals – When allergens trigger mast cells, they release substances like prostaglandins (PGs), leukotrienes (LTs), and chemokines, which cause inflammation.
• Eosinophils contribute to inflammation – These white blood cells release reactive oxygen species (ROS), enzymes, and more chemokines, worsening inflammation.
• Th2 cells are involved – These immune cells help drive the allergic response and activate eosinophils.
• Airway narrowing occurs – The inflammation leads to swelling and thickening of airway walls, reducing the lumen (airway opening), increasing resistance, and making it harder to breathe.

Question 7

Outline the role of key immune cells and inflammatory mediators in allergic asthma.

Answer 7

Question 8

Describe the mechanisms of action by which beta2 agonist and corticosteroid drugs treat the pathophysiology of asthma.

Answer 8