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Unformatted text preview: 1 Pulmonary Physiology Respiratory neurons in brain stem sets basic drive of ventilation descending neural traffic to spinal cord activation of muscles of respiration Ventilation of alveoli coupled with perfusion of pulmonary capillaries Exchange of oxygen and carbon dioxide Respiratory Control System Perfusion-----> Nerve Impulses Nerve Impulses Ventilation Diffusion Force, displacement Pco2, Po2, pH Mechanoreceptors Blood Respiratory membrance Lung & Chest Wal Respiratory Muscles Spinal Cord Respiratory center-Medul a Chemoreceptors Cerebral Cortex Respiratory Centers Located in brain stem Dorsal & Ventral Medullary group Pneumotaxic & Apneustic centers Affect rate and depth of ventilation Influenced by: higher brain centers peripheral mechanoreceptors peripheral & central chemoreceptors Muscles of Ventilation Inspiratory muscles- increase thoracic cage volume Diaphragm, External Intercostals, SCM, Ant & Post. Sup. Serratus, Scaleni, Levator Costarum Expiratory muscles- decrease thoracic cage volume Abdominals, Internal Intercostals, Post Inf. Serratus, Transverse Thoracis, Pyramidal Ventilation-Inspiration Muscles of Inspiration-when contract thoracic cage volume (uses 3% of TBE) diaphragm drops floor of thoracic cage external intercostals sternocleidomastoid anterior serratus scaleni serratus posterior superior levator costarum (all of the above except diaphragm lift rib cage) Ventilation-expiration Muscles of expiration when contract pull rib cage down thoracic cage volume (forced expiration rectus abdominus external and internal obliques transverse abdominis internal intercostals serratus posterior inferior transversus thoracis pyramidal Under resting conditions expiration is passive and is associated with recoil of the lungs 2 Movement of air in/out of lungs Considerations Pleural pressure negative pressure between parietal and visceral pleura that keeps lung inflated against chest wall varies between -5 and -7.5 cmH 2 O (inspiration to expiration Alveolar pressure subatmospheric during inspiration supra-atmospheric during expiration Transpulmonary pressure difference between alveolar P & pleural P measure of the recoil tendency of the lung peaks at the end of inspiration Compliance of the lung V/ P At the onset of inspiration the pleural pressure changes at faster rate than lung volume- z hysteresis z Air filled lung vs. saline filled lung Easier to inflate a saline filled lung than an air filled lung because surface tension forces have been eliminated in the saline filled lung Pleural relationships-lung & chestwall forces Effect of Thoracic Cage on Lung Reduces compliance by about 1/2 around functional residual capacity (at the end of a normal expiration) Compliance greatly reduced at high or low lung volumes...
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This note was uploaded on 05/03/2011 for the course PHYS 339 taught by Professor Free during the Spring '11 term at Palmer Chiropractic.
- Spring '11