Resp 23 - Transport of CO2 from the Tissues

What is CO2 production at rest?

200-250 mL/min

Under resting conditions, how much CO2 is transported from the tissues?

4-5 mL of CO2/100 mL blood

Describe the Haldane Effect

An increase in O2 will shift the CO2 dissociation curve right, decreasing the affinity for CO2 A decrease in O2 will shift the curve to the left, increasing the affinity for CO2

How do HCO3- and Cl- exchange in the lungs?

HCO3- and Cl- exchange in reverse from tissues Cl- moves into plasma and HCO3- moves into erythrocytes to maintain the CA reaction

The carbonic acid reaction for transport of CO2 is faster in the (plasma/RBC)?

RBC

In the lungs, what effect occurs that increases Hb's affinity for O2?

Reverse Bohr effect

What does the CO2 dissociation curve show us?

Shows the CO2 content of whole blood (vol%) plotted against PCO2 (mmHg) of blood

How does the formation of carbamino Hb affect Hb's affinity for O2?

The formation of carbamino Hb decreases the affinity of Hb for O2. O2 is unloaded and release into tissues

Describe the Bohr Effect as it relates to the Oxygen Dissociation Curve.

The oxygen dissociation curve shifts to the right and facilitates the unloading of O2 for release to tissues

Some plasma CO2 reacts with plasma proteins by combining with terminal amine groups forming __________.

carbamino compounds

CO2 is made at the ______ level and transported into the ______.

* venous * lungs

Transport of CO2 by the RBC Intracellular CO2 reacts (rapidly/slowly) with water via ___________ present in the RBC.

* very rapidly * carbonic anhydrase

Transport of CO2 by the plasma * Solubility coefficient of CO2 is ____ x that of O2 * Diffuses ~____ x faster than O2 How much CO2 can dissolve in 100 mL of blood at 37C?

* 21 * 20 * 0.003 x 20 = 0.06 * 0.06 mL CO2/mmHg PCO2 can dissolve in 100 mL blood at 37C

Arterial blood CO2 content * _____ mL CO2/100 mL blood * PaCO2 = ______ mmHg * pH of ______

* 48 * 40 * 7.4

Transport of CO2 * Physically dissolved = ____% * As bicarbonate ion = ____% * Combined with amino acids = ____%

* 5% * 85% * 10%

Venous blood CO2 content * ______ mL CO2/100 mL blood * PvCO2 = ______ mmHg * pH of _______

* 52.5 * 45 * 7.36

* ____ diffuses from pulmonary capillaries into alveoli following its pressure gradient. * ____ enters pulmonary capillaries from alveoli following its pressure gradient

* CO2 * O2

Haldane effect relates (CO2/O2) transport Bohr effect relates (CO2/O2) transport

* CO2 * O2

* Carbonic anhydrase reaction generates _____ & ______. * H+ are buffered by the _______. * Combines with Hb to form HHb --> Hb affinity for O2 is (increased/decreased)

* H+ and HCO3- * deoxygenated Hb * decreased (Bohr)

Chloride Shift * _____ accumulates inside erythrocytes and is exchanged by ___________ for ____ in the plasma * There is a ______ exchange * Chloride shift: ____ enters plasma & _____ enters erythrocytes * How does this affect the cell membrane? * The formation and subsequent addition of _______ to the plasma is the major mechanism for _______ in the blood.

* HCO3-; facilitated diffusion; Cl- * 1:1 * HCO3-; Cl- * This preserves electrical neutrality across the erythrocyte cell membrane * HCO3-; CO2 transport

* In the lung, there is a displacement (unloading) of CO2 from HHb and O2 combines with HHb yielding ____ & _____. * Carbonic anhydrase reaction reverses by the law of ______.

* Hbo2 & H+ * Law of Mass Action

Compare the CO2 dissociation curve with the oxyhemoglobin dissociation curve.

* The shape is more linear and has a steeper slope * For a small change in partial pressure, there is a greater change in CO2 content

Transport of CO2: Physically Dissolved * How is CO2 transported into plasma? * Total CO2 amount of venous or arterial blood is _____% of total CO2 content * How do we calculated how much is dissolved?

* Transported in the plasma in physical solution as a gas * 5% * Venous = 0.06 x 45 mmHg = 2.7 mL CO2/100 mL blood * Arterial = 0.06 x 40 mmHg = 2.4 mL CO2/100 mL blood 2.7-2.4 = 0.3 mL CO2/100 mL blood

In the RBC, CO2 combines with the terminal amine group of Hbg to form ____________. Hbg can carry both O2 & CO2, how does one affect the other?

* carbaminohemoglobin (carbamino compounds) * The presence of one interferes with the binding of the other

* In addition to dissolved CO2, some plasma CO2 is converted to ________. * In plasma, CO2 reacts very slowly with water in the _______. * What happens?

* carbonic acid * carbonic acid reaction * Some of the carbonic acid dissociates into small amount of bicarbonate CO2 + H2O --> H2CO3 --> H+ + HCO3-

In the lung, the RBC intracellular H+ (increases/decreases) and pH (increases/decreases) The oxyhemoglobin dissociation curve shifts to the (left/right)

* decreases; increases * left

Transport of CO2 by the RBC - PCO2 is (low/high) in the tissues - CO2 diffuses from ______ into ______ into ______.

* high * cells --> systemic capillaries --> erythrocytes

What two effect occur in the tissue?

* increased PCO2 = Bohr * decreased PO2 = Reverse Haldane

What two effects occur in the lungs?

* increased PO2 = Haldane * decreased PCO2 = Reverse Bohr

* The position of the CO2 curve is affect by the _______ * This is due to the _____ effect

* oxygen tension (PO2) * Haldane

A small quantity of CO2 is dissolved in the _____ of the erythrocyte.

ICF