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Dalton's law of partial pressures
Total pressure exerted by mixture of gases = sum of pressures exerted by each gas
- Partial pressure:
- exerted by each gas in mixture
- proportional to its percentage in mixture
Gas mixtures in contact with liquid
–Each gas dissolves in proportion to its partial pressure
–At equilibrium, partial pressures in two phases will be equal
–Amount of each gas that will dissolve depends on
- •Solubility–CO2 20 times more soluble in water than O2; little N2
- dissolves in water
•Temperature–as temperature rises, solubility decreases
Bohr effect- Hb-O2 bond weakens à oxygen unloading where needed most
The Bohr effect, on the other hand, describes how carbon dioxide and H+ affect the affinity of hemoglobin for oxygen. High CO2 and H+ concentrations cause decreases in affinity for oxygen, while low concentrations cause high affinity for oxygen.
- Reflex (inflation reflex)
–Stretch receptors in pleurae and airways stimulated by lung inflation
•Inhibitory signals to medullary respiratory centers end inhalation and allow expiration
•Acts as protective response more than normal regulatory mechanism
The Haldane effect describes how oxygen concentrations determine hemoglobin's affinity for carbon dioxide. For example, high oxygen concentrations enhance the unloading of carbon dioxide. The converse is also true: low oxygen concentations promote loading of carbon dioxide onto hemoglobin. In both situations, it is oxygen that causes the change in carbon dioxide levels.
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