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Lecture 30

Gas Exchange

TermDefinition
Partial Pressures Gas equivalent to concentration. Sea level:760 mmHG=600 N2+160 O2.CO2=.03 mmHg. Gases indep of one another. Air in lungs is water saturated
Alveolar Air PO2=100mmHG,PCO2=40.Venous blood:PO2=40,PCO2=46
Diffusion Across Alveolar Wall gases follow partial pressure gradients capillary gases match tissue it goes through. O2:O2 enters pulmonary capillaries until PO2 is 100. CO2:CO2 leaves pulmonary capillaries until PCO2 is 40
Pulmonary Circulation Lower BP than aorta. ~15-20mmHg of MAP pf pulmonary artery.
Ventilation/Perfusion Ratio Ventilaiton and perfusion normally well matched,0.8 areas that open alveoli:get more blood. As need for gas exchange raises both and ventilation raises in new lung areas
Tissue Gas Exchange Reverse of Lungs. O2:100mmHg of arterial blood loses O2 to 40mmHG tissur=e until capillary is 40mmHg. CO2:40mmHg arterial blood receives CO2 from 46mmHg tissue until capillary is 46 mmHg
Oxygen Transport 1.5% carried by dissolved O2. 98.5% carried by binding to hemoglobin
Oxygen-Hemoglobin Binding Sigmodal curve-cooperativity btw 4-5 subunits
Sleep Region At tissues-fall in PO2-unloads O2. At lower PO2,even more O2 delivery "work hard,get oxygen"
Plateau Region At lungs-all Hb is O2 bound-no effect of extra O2
Bohr Effect CO2,acid,shift Hb-O2 curve to the right. More O2 unloading at given PO2
Carbon Monoxide 2 effects. Binds Hb 200x stronger than O2-less Oa available. Never dissociates-must lyse RBC to lose CO
Hypoxia Low blood O2. low air O2 air=high altitude or O2 deprivation. High altitude ethnic groups-higher Hb even at sea level.sea level ethnic groups-low O2 training raises Hb,lose when return to sea level
Hyperpoxia Breathe high O2 air-no additional Hb binding (already full). raises dissolved O2 may lower breathing rate-benefit only psychological
Carbon Dioxide Transport 10% dissolved, 30% bound to plasma protein and Hb. 60% converted to bicarbonate by carbonic anhydrase (CA) CA catalyzes:H2O+CO2 leads to H2CO3-HCO3- +H+
Carbonic Anhydrase In RBC's. Converts CO2 leads to bicarbonate at tissues as CO2 added. At lungs,reversal:bicarb,CO2 then breathed out
Hypocapnia Low CO2 hyperventilation dec CO2 in blood leads to faint breathing into bad raises CO2,back to normal.
Hypercapnia High CO2 raises breathing rate raises CO2 in blood strongest stimulus for inc respiration
Created by: danamarie9323