BIOL122 Lecture Notes - Lecture 7: Mast Cell, Bronchospasm, Pollen Count
Asthma:
Neural control of airway smooth muscle:
• There is only parasympathetic innervation of bronchial smooth muscle (via
vagus nerve)
• PNS releases acetylcholine which acts on muscarinic receptors in smooth
muscle to bronchonstriction
• There is no sympathetic innervation of bronchial smooth muscle
• Circulating adrenaline (SNS) acts of B2 adrenoceptors in smooth muscle to
bronchodilation
Restrictive lung disorder: lung volumes are limited in restrictive disease
• Difficulty getting air into lungs
• Compliance is a measure of the lungs ability to stretch and expand
• Reduced compliance decreases expansion of the lung tissue, with
decreased total lung capacity
• Reduced compliance associated with restrictive lung diseases such as
pulmonary fibrosis, tumours, obesity, arthritis, kyphoscoliosis
Obstructive lung disorders: Difficulty getting air out of lungs
• Increased resistance to airflow due to partial or complete obstruction at any
level from the trachea to terminal and respiratory bronchioles
• Expiratory obstruction may result from:
- Anatomic airway narrowing or loss of elastic recoil of the lung
• Emphysema
• Chronic bronchitis
• Asthma
Why is breathing out harder in obstructive disease than breathing in?
Document Summary
Obstructive lung disorders: difficulty getting air out of lungs. Increased resistance to airflow due to partial or complete obstruction at any level from the trachea to terminal and respiratory bronchioles: expiratory obstruction may result from: Anatomic airway narrowing or loss of elastic recoil of the lung: emphysema, chronic bronchitis, asthma. Asthma: chronic inflammatory disorder of airways: exercise is a trigger for intrinsic, non- allergy induced, attacks. Intrinsic causes are most likely due to parasympathetic stimulation dominating in bronchiole regulation: extrinsic causes are due to allergy- induced immune reactions. Intermittent airway obstruction (i. e. airflow) is caused by several factors. Bronchoconstriction of smaller airways caused by trigger- induced spasm of airway smooth muscle. Thickening of airway walls due to allergen- induced inflammation. Plugging of airways due to expensive secretion of very thick mucus. Asthma: hygiene hypothesis: frequent challenge to the immune system is needed for balanced development and prevention of overreaction to allergens. Pathophysiology of asthma involves the type 1 hypersensitivity reaction.
