11 terms

Bohr Effect

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What is the Bohr Effect?
-An increase in CO2 or H+ ion concentration (decrease in pH) in the blood causes a rightward shift of the O2 dissociation curve (i.e., causes O2 to dissociate from hemoglobin).
What two other physiological factors can shift the oxygen curve to the right?
-An increase in temperature- happens during exercise- even in healthy individuals

-An increase in DPG- 2,3-diphosphoglycerate
An increase in DPG is seen what kinds of patients?
-Patients who suffer from chronic lung disease and/or chronic hypoxias
What does shifting the oxygen dissociation curve to the right mean?
-Meaning that a given O2 partial pressure, less O2 is bound to hemoglobin
How does a rightward shift in the oxygen dissociation curve influence the O2 delivery to the tissues?
-Δ1 : the additional amount of O2 delivered to the cells due to the Bohr Effect (because Pco2 in the capillary blood increases from 40 to 46 mmHg at the same time when the Po2 in the capillary blood is reduced from 100 to 40 mmHg).

-Δ2 : the total amount of O2 delivered to the peripheral tissue in each 100 ml of blood.
Bohr Effect Summarized
-When the arterial blood is going to a tissue capillary, oxygen content in the arterial blood is represented by point (a) on the graph

-The oxygen content in the venous blood is represented by point (v) on the graph

-The total amount of O2 delivered to the tissues is the difference between (a) and (v)

-A large amount of the Delta 2 on the graph is generated by the Bohr Effect (Delta 1)
What is the Bohr Effect in the alveolar capillary?
-It is reversed from what is seen in the tissue capillary

-In the alveolar capillary, the blood that enters the capillary is venous blood (v)

-The blood found at the end of the alveolar capillary is arterial blood (a)

-Still the same Delta 2- but going from (v) to (a) in the alveolar capillary- instead of (a) to (v)
What happens during exercise to the arterial PO2 and PCO2?
-During exercise, arterial PO2 and PCO2 does not change (100 mmHg and 40 mmHg, respectively)
What happens during exercise to the venous PO2 and PCO2?
-During exercise, the venous PO2 drops to 35 mmHg and the PCO2 increases to 50 mmHg

-This all due to the increased metabolism
During exercise, what happens to the oxygen dissociation curve due to an even higher PCO2 (50 mmHg vs. 46 mmHg)?
-This will result in the oxygen dissociation curve shifting even more rightward

-So the oxygen delivery from the arterial blood will be even greater (Delta 3) than what is seen in normal resting conditions

-Furthermore, this will result in a greater uptake of O2 in the oxygen alveolar capillary (since the venous blood entering those capillaries will have a PCO2 of 50 mmHg)
The Bohr Effect is more pronounced in what conditions?
-This effect is even more pronounced during exercise and also in patients with lung diseases