BIOS1170 Lecture 6: Week 6 Notes
4 Sep 2018
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From atmosphere to lungs in 2 phases : atmosphere > upper airways = due to bulk flow, between upper airways and alveoli = due to diffusion, and some bulk flow of gas in/out alveoli. Slow process > alveolar gas compositions change slowly, alveolar gas not replaced on each breath. Concentration gradients must be maintained by bulk flow for diffusion to occur. Changes in lung volume: - responsible for pressure gradients down which gases move. Pressure changes in alveoli > bronchioles > upper airways. When pressure in upper airway exceeds atmospheric pressure, expiration occurs. Lung/chest wall are elastic opposes inflation lung volume increases > elastic forces increase. Airways represent a resistance to gas flow. Impedance resistance to gas flow (determined by frequency/flow rate) Contract diaphragm lower dome, lift/flare ribs, parasternal/scalenes active. Exercise more activated with increasing ve. Respiratory disease recruitment other ribcage muscles/neck muscles if there is high lung volume, high resistance. Expiratory muscles mainly relies on elastic recoil.
