Respiratory Physiology: Outline

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Respiratory Physiology Outline
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Alveolar-Blood Interface
Membrane between Alveoli Capillary is VERY VERY
THIN ..increases diffusion rate
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Simple Diffusion Partial Pressures
Rate of Diffusion Concentration Gradient
Gas Concentrations are represented by Partial
Pressures!
High P
Low P
Diffusion is best over VERY VERY short
distances..that is why alveoli-blood interface
is so thin
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Diffusion between Alveoli Blood OXYGEN
Blood leaving Lungs has High PO2
Blood entering Lungs has Low PO2
Blood leaving Tissue has Low PO2
Blood entering Tissue has High PO2
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Diseases affecting O2 Diffusion
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Oxygen Transport in Blood

• O2 diffuses into blood from Alveoli
• 98 of diffused oxygen enter RBC
• binds to Hemoglobin (Hb)
• 3) 2 of oxygen remains in plasma
• 4) At tissue, Hb O2 dissociate
• 5) O2 dissolves through plasma into ISF

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Hemoglobin in RBC allows blood to carry 5000
more oxygen!
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Hemoglobin dissociation Curve
100 4 hemes-O2 75 3 hemes-O2
4 hemes per Hemoglobin Molecule
Each Heme carries 1 O2 molecule
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Hemoglobin has a built in reserve capacity!
Alveoli
PO2 100 mm Hg
100 4 hemes-O2
PO2 20
PO2 100
Circulatorysystem
PO2 100
PO2 20
25 1 heme-O2
EXERCISING MUSCLE
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Anemia too few RBC
Iron Deficiency no heme
B12 or Folate Deficiency reduced DNA synthesis
Sickle Cell hereditary
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EPO a performance enhancer
EPO Hormone controlling RBC synthesis
Blood Doping EPO supplement more RBC more
O2 carrying capacity
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Diffusion between Alveoli Blood CO2
Blood entering Lungs has High PCO2
Blood leaving Lungs has Low PCO2
Blood entering Tissue has Low PCO2
Blood leaving Tissue has High PCO2
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Carbon Dioxide Transport in Blood

• 1) Dissolved CO2 7

• Diffusion from tissues to capillaries
• Diffusion from venous blood to alveolar air

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Carbon Dioxide Transport in Blood

• 2) Hemoglobin transport 23

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• CO2 diffuses into blood from tissues
• CO2 binds to Hemoglobin (Hb)
• 3) In lungs, Hb CO2 dissociate
• 4) CO2 dissolves into plasma and
• diffuses to air in alveoli

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Carbon Dioxide Transport in Blood

• 3) Bicarbonate Ion 70

• CO2 dissolves into plasma
• CO2 enters RBC and combines with water
• Converted to HCO3- Hb-H
• by CARBONIC ANHYDRASE (CA)
• 4) Cl- ion is exchanged for HCO3-
• in CHLORIDE SHIFT
• 5) HCO3- is carried in plasma to lungs
• 6) Reverse of 3 4
• 7) CO2 dissolves in plasma and diffuses
• to alveolar air

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HCO3- (Bicarbonate) is the most important pH
buffer in blood Chloride Shift maintains RBC
membrane electrical neutrality Hb-H helps
maintain pH by using extra H ion from 2)
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Acidosis Poor CO2 elimination

• Why is removing CO2 important?
• Elevated CO2 Hypercapnia
• Acidosis leads to denatured proteins depressed
  brain function

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Control of Ventilation
Chemoreceptor pathways ALWAYS override Voluntary
pathways You cant hold you breath until you
die! This is why you drown!!!!