L10 physiology

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Questions and Answers

What happens to the oxygen dissociation curve when hemoglobin is oxygenated?

It shifts to the right. (correct)

It shifts to the left.

It remains unchanged.

It becomes a sigmoid shape.

What is the primary effect of the Haldane effect?

Increased affinity of hemoglobin for CO2.

Reduction of chloride shift in the tissues.

Release of CO2 when blood is oxygenated. (correct)

Inhibition of O2 release in the lungs.

What role does bicarbonate play in carbon dioxide transport?

It gets converted to CO2 in the lungs. (correct)

It directly binds to hemoglobin.

It acts as an oxygen carrier in the bloodstream.

It enhances the affinity of hemoglobin for oxygen.

What occurs during the chloride shift in red blood cells?

Bicarbonate enters the RBC while chloride exits. Signup and view all the answers

Which of the following statements accurately describes the carbon dioxide dissociation curve?

It is linear and varies between venous and arterial blood. Signup and view all the answers

How does the presence of H+ ions affect hemoglobin's oxygen affinity?

It decreases affinity, facilitating oxygen release. Signup and view all the answers

How does the partial pressure of CO2 affect oxygen transport?

Lower CO2 enhances the unloading of oxygen. Signup and view all the answers

What is the effect of carbon monoxide poisoning on oxygen transport?

It reduces hemoglobin saturation and oxygen delivery. Signup and view all the answers

What is the primary mechanism of oxygen transport in the blood?

Dissolved in plasma Signup and view all the answers

What factor enhances the unloading of oxygen from hemoglobin according to the Bohr effect?

Increased temperature Signup and view all the answers

How does the oxygen hemoglobin dissociation curve appear?

Sigmoid shaped Signup and view all the answers

Which statement correctly describes the chloride shift?

Chloride ions move into red blood cells with bicarbonate ions moving out Signup and view all the answers

What is the role of hemoglobin in oxygen transport?

It binds to oxygen in the lungs and releases it in tissues Signup and view all the answers

Which conditions lead to a shift to the right in the oxygen hemoglobin dissociation curve?

Increased temperature and PCO2 Signup and view all the answers

What describes the Haldane effect in relation to carbon dioxide transport?

Increased CO2 uptake when hemoglobin releases oxygen Signup and view all the answers

Which of the following is true about the transport of carbon dioxide in blood?

It is transported as bicarbonate and carbamino compounds Signup and view all the answers

Which mechanism of carbon dioxide transport occurs in the form of bicarbonate?

Bicarbonate Signup and view all the answers

What does an increase in P50 indicate regarding hemoglobin's affinity for oxygen?

Decreased affinity for oxygen Signup and view all the answers

What occurs during the chloride shift in tissue capillaries?

Chloride ions enter the RBC and bicarbonate leaves. Signup and view all the answers

How is the oxygen dissociation curve affected in cases of anemia?

Both PO2 and % saturation of hemoglobin are normal. Signup and view all the answers

What effect does CO poisoning have on hemoglobin?

Forms carboxyhemoglobin which cannot bind to O2. Signup and view all the answers

What is the primary impact of the Bohr effect on oxygen transport?

Facilitates oxygen release in tissues with high CO2 levels. Signup and view all the answers

What defines the Haldane effect regarding carbon dioxide transport?

CO2 is more readily released from hemoglobin in the presence of O2. Signup and view all the answers

What is the normal value for P50 in hemoglobin saturation?

24-28 mmHg Signup and view all the answers

Study Notes

Diffusion and Transport of Gases

Learning Objectives: List mechanisms of oxygen and carbon dioxide transport, describe the reaction between hemoglobin and oxygen, explain oxygen dissociation curves, describe the Bohr effect, describe chloride shift, explain carbon dioxide dissociation curves, and describe the Haldane effect.

Gas Exchange in Lungs & Tissues

Exchange Mechanism: Exchange of gases between lungs and blood, and at tissue level, occurs passively via diffusion, determined by pressure gradients.
Alveolar Membrane: High surface area (70 sq.m) and thinness (0.5µm) make it ideal for diffusion.
Pressure Gradients: Gradients for O2 (100-40 mmHg) and CO2 (46-40 mmHg) drive gas movement. Specific pressure values are given for inspired air, trachea, venous blood, arterial blood, pulmonary capillaries, and tissue capillaries.

Gas Exchange in the Lungs

PO2 and PCO2: PO2 in alveoli is 100 mmHg, in pulmonary capillaries is 40 mmHg. This drives oxygen into the capillaries. PCO2 in pulmonary capillaries is 46 mmHg.
Average Arterial Blood Gases: PO2 is 100 mmHg, PCO2 is 40 mmHg.
Gas Transfer Capacity: May be impaired by membrane thickening or reduced surface area.

Transport of O2 in the Blood

Dissolved Form: 0.3 ml/100 ml of blood, establishes PO2 of blood, regulates breathing, and determines hemoglobin loading.
Oxyhemoglobin: Each hemoglobin molecule carries four oxygen molecules. Oxygen carrying capacity of 1 gram of hemoglobin is 1.34 ml of O2, in 100 ml of blood is 20ml oxygen.

Bohr Effect in the Tissues

Unloading Conditions: Increased PCO2, temperature, 2,3-DPG, and decreased pH enhance oxygen unloading from hemoglobin.
Oxygen Release: Helps oxygen unload from hemoglobin, particularly in actively contracting muscles.
Myoglobin: Skeletal muscle myoglobin binds oxygen at low PO2 and releases it at very low PO2

Oxygen Hemoglobin Dissociation Curve

Sigmoid Curve: The curve shows the relationship between PO2 and hemoglobin saturation.
Plateau Region: High PO2 values show nearly complete saturation.
Steep Region: Curve is steep between 60 and 20 mmHg PO2, critical for oxygen delivery.
P50 Value: Pressure at which Hb is 50% saturated (normal range 24-28 mmHg).
Arterial and Venous Blood: Arterial PO2 is 98 mmHg, saturation 95%; venous PO2 is 40 mmHg, saturation 75%.

P50

Pressure for 50% Saturation: Indicates the pressure at which hemoglobin is 50% saturated with oxygen. Shift to left or right on the curve impacts this value. Factors such as increased temperature, increased DPG, increased CO2, and decreased pH shift the curve to the right and decrease the P50 value. Conversely, decreased temperature, decreased DPG, decreased CO2, and increased pH shift the curve to the left, increasing P50.

CO2 Transport

Mechanisms: CO2 is transported as dissolved CO2 (5%), bicarbonate (70%), and carbaminohemoglobin (25%).
Bicarbonate: The main form, plays a crucial role in acid-base balance and pH maintenance.

Chloride Shift in Tissue Capillaries

CO2 Uptake: CO2 enters red blood cells and combines with water, forming carbonic acid, which then dissociates into bicarbonate and hydrogen ions.
Bicarbonate Movement: Bicarbonate ions exit the red blood cell and chloride ions enter to maintain electrical neutrality.
Chloride Shift: This exchange process is called the chloride shift or Hamburger's shift.

O2 Dissociation Curve in Anemia and CO Poisoning

Anemia: Oxygen content in the blood is reduced, but PO2 and hemoglobin saturation may remain normal. The curve remains similar, but the overall oxygen-carrying capacity is decreased.
CO Poisoning: Carbon monoxide binds to hemoglobin much more strongly than oxygen. The carboxyhemoglobin cannot release oxygen, reducing oxygen delivery. Significant shift to the left, making oxygen dissociation difficult.

CO2 Transport - Summary

Chloride Shift Reversal: In the lungs, the chloride shift reverses. Chloride ions leave red blood cells and bicarbonate ions enter, facilitating CO2 release. CO2 is then eliminated from the body.

CO2 Dissociation Curve

Linear Curve: The CO2 dissociation curve follows a fairly linear pattern in both venous and arterial blood.
Venous CO2: Venous blood has a PCO2 of 46 mmHg and a volume of 52%.
Arterial CO2: Arterial blood has a PCO2 of 40 mmHg and a volume of 48%.

Haldane Effect

Oxygen Effect: Oxygenation of hemoglobin leads to a rightward shift of CO2 dissociation curve, facilitating CO2 release from the blood into the alveoli.
Pressure Gradient: The higher PO2 in the lungs creates a pressure gradient for O2 uptake and CO2 release.
Chloride shift: Reverse chloride shift facilitates CO2 release.

Learning Resources

Text Book: Marieb EN. Human Anatomy and Physiology, 9th Edition, Pearson International Edition; 2014. ISBN-13: 978-1-2920-2649-7. Chapter 22, pp. 892-897.
PowerPoint: Presentation materials available on Moodle.

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Description

This quiz explores the mechanisms of oxygen and carbon dioxide transport in the body. It covers critical concepts like hemoglobin reactions, oxygen dissociation curves, and the roles of the Bohr effect and chloride shift in gas exchange. Test your understanding of the diffusion process across alveolar membranes and the resulting pressure gradients in the lungs.