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咳嗽生理机制

咳嗽生理机制

cough-physiology

Cough: Physiology Mass or particulate matter in the throat & airways ↑ pressure on mucosa Pressure on rapidly and slowly adapting mechanoreceptors Mechanoreceptor activation opens ion channels on vagus neurons Authors: Calvin Howard Reviewers: Nilani Sritharan Ciara Hanly Yonglin Mai (麦泳琳)* Yan Yu* Stephen Field* * MD at time of publication Systemic immune reaction Inflammation of alveoli Cytokine release Cytokines bind to sensory neurons Neurons ↑ receptor sensitivity and number ↑ sensation of stimuli Ionic flux across neuronal membrane Vagus neurons depolarize Thinly myelinated axons (Aδ fibers) General chemicals, heat, cold, and hydrogen ions Transient receptor potential vanilloid (TRPV)/Transient receptor potential ankyrin (TRPA) receptors activate TRPV/TRPA activation opens ion channels on vagus neurons Unmyelinated axons (C fibers) carry depolarization Vagus nerves conduct depolarization to carry depolarization SUMMARY Afferent pathways activated Cough center (medulla) Efferent pathways Respiratory muscles nucleus of the solitary tract Medullary nuclei activated, stimulates: Phrenic nerves Diaphragm contraction Spinal nerves External intercostal contraction Vagal nerves Glottis closure Spinal nerves Thoracic, abdominal, and pelvic muscle contraction Vagal nerves Glottis opens, allowing forceful expiration Intrathoracic pressure and volume decrease Volume in lungs increases Intrathoracic pressure increases Mechanical Cough Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published Sept 1, 2019, updated Dec 5, 2021 on www.thecalgaryguide.com