Gas Transport Mechanisms

Question 1

Dalton’s Law of Partial Pressures

Answer 1

the total pressure of atmospheric gas is equal to the sum of the partial pressures of each gas subcomponent

760 mm Hg total

Question 2

normal partial pressure of N2

Answer 2

596 mm Hg, 78.6%

Question 3

normal partial pressure of O2

Answer 3

158 mm Hg, 20.8%

Question 4

normal partial pressure of CO2

Answer 4

0.3 mm Hg, 0.04%

Question 5

Atmospheric Pressure

normal partial pressure of H2O

Answer 5

5.7 mm Hg, 0.5%

Question 6

Alveolar Gas: composition will

Alveolar Gas

Answer 6

compensation will differ from atmospheric gas

Question 7

Why does aveolar gas differ from atmospheric gas?

Answer 7

1. incomplete replacement of Alveolar air with Atmospheric air
2. O2 is constantly being absorbed by Alverolar capillaries
3. CO2 is leaving pumonary capillaries and entering alveoli
4. atmospheric air is usually much drier than alveolar air

partial pressure of water will displace other gases there is moisture in the airway passages

Question 8

Alveolar Gas Partial Pressure

Answer 8

N2: 573 mm Hg
O2: 100 mm Hg
CO2: 40 mm Hg
H2O: 47 mm Hg

Question 9

Arterial Gas Partial Pressure

Answer 9

N2: 573 mm Hg
O2: 95 mm Hg
CO2: 40 mm Hg
H2O: 47 mm Hg (ignore)

O2 is less than alveolar gas because the lungs use oxygenated blood to supply their tissues

Question 10

Venous Side of Capillaries Partial Pressures

Answer 10

N2: 573 mm Hg
O2: 40 mm Hg
CO2: 46 mm Hg
H2O: 47 mm Hg (ignore)

O2 gets dumped off in tissues, CO2 diffuses from tissues into capillaries

Question 11

Why does CO2 diffuse into the lungs and O2 diffuse into the blood?

Answer 11

the differences in partial pressure
higher O2 in alveolar gas than blood
higher CO2 in blood than alveolar gas

Question 12

3 forms of CO2 in the blood stream

Answer 12

1. HCO3 - 70%
2. bound to hemoglobin - 23%
3. free gas, CO2 - 7%

Question 13

Oxygen-Hemoglobin Dissociation Curve

Answer 13

expressed as % O2 saturation vs partial pressure O2

Question 14

Oxygen-Hemoglobin Dissociation Curve

P50 Value

Answer 14

the pO2 where hemoglobin is 50% saturated

the higher the P50 value, the lower the affinity of hemoglobin for O2

Question 15

Oxygen-Hemoglobin Dissociation Curve

Causes for a Right Shift

Answer 15

1. Low pH (acid)
2. Increase in CO2 (acid)
3. Increase in Temperature
4. Increase in 2,3 DPG (caused by increase in temp or decrease in pH)

higher P50, lower hemoglobin binding affinity

Question 16

Oxygen-Hemoglobin Dissociation Curve

Fetal Hemoglobin has low 2,3 DPG binding therefore:

Answer 16

a higher binding affinity for O2 than maternal blood

left shift of curve

Question 17

DPG at high altitude

Answer 17

increased 2,3 DPG production, O2 less tightly bound, easy to dump off O2 to tissues

Right Shift of curve

Question 18

Erythropoietin

Answer 18

produces RBCs

Question 19

Mountain Sickness

Answer 19

1. Decreased BP
2. decreased air pressure in alveoli
3. Hyperventilation and alkalosis
4. edema in lungs and nervous system
5. potential for coma and death

Question 20

Myoglobin vs Hemoglobin

Answer 20

Myoglobin has higher binding affinity for O2 than hemoglobin

Question 21

Effect of Carbon Monoxide

Answer 21

1. Forms Carboxyhemoglobin(210x more affinity for hemoglobin than oxygen)
2. Displaces O2 binding
3. When bound to 70-80% hemoglobin death results (anemic hypoxia)

treatment with hyperbaric chamber or transfusion

Question 22

The Bends

Answer 22

elevated N2 dissolved in blood due to increased water pressure
causes arterial blockage, joint pain, explossive decompression, air embolism

happens when at depth for too long or rapidly rising to the surface

Question 23

Nitrogen Narcosis

Answer 23

high concentrations of nitrogen have a narcotic effect on the nervous system

Question 24

How to survive swimming to the surface from a submarine?

Answer 24

exhale as you swim up as air in lungs expands during ascent

Question 25

Chloride Shift

Answer 25

1. Excess HCO3- builds up in RBC
2. HCO3- is exchanged with Cl- ions
3. HCO3- enters plasma

Question 26

Carbonic Anhydrase mediates

Answer 26

CO2 + H2O <-> H2CO3 <-> H+ + HCO3-