Physiology 4.2

Question 1

Describe the amount of that dissolves in the plasma.

Answer 1

Only three millilitres of oxygen diss in every litre of plasma.

Question 2

Define the majority of oxygen transportation in the blood.

Answer 2

The majority of oxygen is wrapped up in the haemoglobin protein found inside red blood cells.

Question 3

How does the amount of oxygen in solution in plasma affect the binding to haemoglobin in red blood cells?

Answer 3

The small fraction of oxygen in solution in plasma is incredibly important in determining how much oxygen can bind to haemoglobin in the red blood cells.

Question 4

Do red blood cells and haemoglobin play a role in oxygen delivery to tissues?

Answer 4

Yes, red blood cells and haemoglobin play a crucial role in increasing the arterial oxygen content to meet the oxygen demand of resting tissues.

Question 5

Describe the partial pressure of oxygen in the alveoli and plasma under normal healthy conditions.

Answer 5

Under normal healthy conditions, the partial pressure of oxygen in the alveoli is 100 millimetres mercury, and it is the same in the plasma.

Question 6

Define the role of haemoglobin in oxygen transportation.

Answer 6

Haemoglobin can carry 197 millilitres of oxygen in every litre of blood, increasing the arterial oxygen content when combined with the amount of oxygen in solution in the plasma.

Question 7

Define oxygen extraction and utilization at rest.

Answer 7

At rest, only 25 percent of the oxygen delivered to peripheral tissues is extracted and metabolized.

Question 8

How is oxygen primarily carried in the blood?

Answer 8

Ninety-eight percent of the oxygen in the blood is carried in haemoglobin, a protein found inside red blood cells.

Question 9

Describe the structure of adult haemoglobin.

Answer 9

Adult haemoglobin, or haemoglobin A, consists of four polypeptide chains - two alpha and two beta chains - each associated with a haem group.

Question 10

What is the cooperative binding relationship of oxygen with haemoglobin?

Answer 10

When oxygen binds to haemoglobin, it causes the polypeptide chains to shuffle, making it easier for more oxygen molecules to bind, and conversely, when oxygen leaves, it makes it less attractive for other oxygen molecules to bind.

Question 11

Explain the major determinant of haemoglobin’s oxygen saturation.

Answer 11

The partial pressure of oxygen in the blood, determined by the amount of oxygen in solution, is the major determinant of haemoglobin’s oxygen saturation.

Question 12

Describe the process of oxygen transfer from the alveoli to the red blood cells.

Answer 12

Oxygen is transferred from the alveoli to the red blood cells as the red blood cells effectively suck the oxygen out of the plasma, helping to maintain a partial pressure gradient between the alveoli and the plasma.

Question 13

Define the term ‘saturated haemoglobin’ in the context of oxygen transport.

Answer 13

Saturated haemoglobin refers to the state where each haemoglobin molecule is bound to four molecules of oxygen, effectively sequestering oxygen from the plasma and maintaining the partial pressure gradient.

Question 14

How does the partial pressure gradient between the alveoli and the blood impact oxygen transfer?

Answer 14

As long as there’s a partial pressure gradient between the alveoli and the blood, oxygen will continue to be pulled down from the alveoli into the blood, facilitating the transfer of oxygen.

Question 15

Describe the relationship between the partial pressure of oxygen and the saturation of haemoglobin.

Answer 15

There’s a sigmoidal relationship between the partial pressure of oxygen and the saturation of haemoglobin, with a plateau at the top end of the curve, indicating very little change in saturation until the partial pressure of oxygen falls below 60 millimetres mercury.

Question 16

Do red blood cells significantly impact the oxygen content of the blood?

Answer 16

Yes, by adding red blood cells to the circulation, the oxygen content of the blood increases significantly from three millilitres per litre to 200 millilitres per litre, with most of the oxygen being wrapped up in the red blood cells’ haemoglobin.

Question 17

Describe the impact of a 40% fall in the partial pressure of oxygen in plasma on the saturation of haemoglobin.

Answer 17

A 40% fall in the partial pressure of oxygen in plasma creates only about a 7-8% fall in the total oxygen content of the blood, as at 60 millimetres mercury partial pressure of oxygen, the haemoglobin is still 90% saturated.

Question 18

How quickly does the saturation of haemoglobin occur after contact with the alveoli?

Answer 18

The saturation of haemoglobin is complete after only a quarter of a second of contact with the alveoli, even though the blood is in contact with the alveoli for about three quarters of a second, indicating a rapid loading of haemoglobin with oxygen.

Question 19

Define the term ‘oxyhaemoglobin’ and its reversibility.

Answer 19

Oxyhaemoglobin is formed when haemoglobin reacts with oxygen, and this reaction is reversible, meaning that as the partial pressure falls, the reaction can move the other way, allowing the release of oxygen to the peripheral tissues.

Question 20

Describe the relationship between the pressure of oxygen and amount of oxygen that binds to haemoglobin.

Answer 20

The pressure of oxygen affects the amount of oxygen that binds to haemoglobin, with a steep impact once the partial pressure falls below 60 mmHg.

Question 21

Define the term anaemia and its causes.

Answer 21

Anaemia is a condition where the oxygen carrying capacity of the blood is compromised. It can be caused by iron deficiency, haemorrhage, or vitamin B12 deficiency.

Question 22

How does the oxygen-haemoglobin dissociation curve change in anaemia?

Answer 22

In anaemia, the oxygen-haemoglobin dissociation curve shifts to the right, indicating a decreased affinity of haemoglobin for oxygen.

Question 23

Describe the oxygen saturation levels in arterial and venous blood.

Answer 23

Arterial blood is normally 97-98% saturated with oxygen, while venous blood is 75% saturated, reflecting the oxygen content of peripheral tissues.

Question 24

Do small changes in the partial pressure of oxygen have a significant impact on the amount of oxygen that binds to haemoglobin?

Answer 24

Yes, small changes in the partial pressure of oxygen in solution have a much bigger impact on the amount of oxygen that binds to haemoglobin, especially on the steep part of the oxygen-haemoglobin dissociation curve.

Question 25

How does the co-operative binding relationship between oxygen and the haem groups become important at low partial pressure of oxygen?

Answer 25

At low partial pressure of oxygen, the co-operative binding relationship becomes important as haem groups start to have a much lower affinity for oxygen, leading to the release of more oxygen molecules from haemoglobin.

Question 26

Describe the significance of the amount of oxygen in solution in the plasma.

Answer 26

A big fall in the amount of oxygen in solution in the plasma has a relatively small impact on the total amount of oxygen, as most of the oxygen is contained within haemoglobin.

Question 27

What is the normal partial pressure of oxygen in resting tissues?

Answer 27

The normal partial pressure of oxygen in resting tissues is 40 mmHg.

Question 28

Define the term oxyhaemoglobin curve.

Answer 28

The oxyhaemoglobin curve shows the relationship between the partial pressure of oxygen and the saturation of haemoglobin with oxygen, indicating the amount of oxygen bound to haemoglobin at various partial pressures of oxygen.

Question 29

Describe the relationship between partial of oxygen and saturation haemoglobin.

Answer 29

The partial pressure of oxygen determines the saturation ofemoglobin, with a normal partial pressure resulting in normal haemoglobin saturation.

Question 30

Do red blood cells become fully saturated with oxygen in anaemia?

Answer 30

Yes, red blood cells can be fully saturated with oxygen in anaemia, as long as the partial pressure of oxygen is normal.

Question 31

Define partial pressure of oxygen.

Answer 31

Partial pressure of oxygen refers to the amount of oxygen that is in solution and determines how much oxygen binds to haemoglobin.

Question 32

How does anaemia affect the partial pressure of oxygen in systemic arterial blood?

Answer 32

Anaemia does not affect the partial pressure of oxygen in systemic arterial blood; it remains the same.

Question 33

Describe the impact of anaemia on total blood oxygen content.

Answer 33

In anaemia, the total blood oxygen content may be significantly compromised despite a normal plasma partial pressure of oxygen.

Question 34

How does the amount of haemoglobin in red blood cells affect oxygen binding?

Answer 34

A deficiency in red blood cells or haemoglobin results in less bulk haemoglobin available to bind oxygen, but the existing haemoglobin becomes fully saturated at a normal partial pressure of oxygen.

Question 35

Explain the relationship between partial pressure of oxygen and total oxygen content.

Answer 35

A decrease in partial pressure of oxygen leads to a decrease in total oxygen content, as the partial pressure determines how much oxygen binds to haemoglobin.

Question 36

Describe the impact of iron deficiency on oxygen binding in anaemia.

Answer 36

Iron deficiency may reduce the number of oxygen binding sites available for oxygen to bind, but the available iron binding sites will be bound to oxygen as long as the partial pressure of oxygen is normal.

Question 37

Describe the Bohr effect.

Answer 37

The Bohr effect describes the phenomenon where a decrease in pH, an increase in partial pressure of carbon dioxide, or an increase in body temperature causes the oxyemoglobin curve to shift to the right, reducing the affinity of haemoglobin for oxygen and aiding oxygen unloading at peripheral tissues.

Question 38

Define DPG (diphosphoglycerate).

Answer 38

DPG, or diphosphoglycerate, is a by-product of red blood cell metabolism that can affect the affinity of haemoglobin for oxygen.

Question 39

How does the oxyhaemoglobin curve shift in response to certain stimuli?

Answer 39

A decrease in pH, an increase in partial pressure of carbon dioxide, and an increase in body temperature cause the oxyhaemoglobin curve to shift to the right, reducing the affinity of haemoglobin for oxygen.

Question 40

Describe the impact of hypothermia on oxygen unloading at peripheral tissues.

Answer 40

Hypothermia increases the affinity of haemoglobin for oxygen, causing it to hold onto oxygen and reducing oxygen unloading at peripheral tissues.

Question 41

Do changes in pH, partial pressure of carbon dioxide, and body temperature affect the affinity of haemoglobin for oxygen?

Answer 41

Yes, changes in pH, partial pressure of carbon dioxide, and body temperature can alter the affinity of haemoglobin for oxygen, affecting oxygen unloading at peripheral tissues.

Question 42

What are the factors that cause the oxyhaemoglobin curve to shift along the x axis?

Answer 42

The factors include a change in pH, a change in partial pressure of carbon dioxide in arterial plasma, change in body temperature, and a change in 2,3 diphosphoglycerate (DPG).

Question 43

Describe the role of diphosphoglycerate in red blood cells.

Answer 43

Diphoglycerate reduces the affinity of red blood for oxygen, aiding in oxygen un to peripheral tissues in situations of hypoxia.

Question 44

What are some situations in which red blood cells produce more diphosphoglycer?

Answer 44

Red blood cells produce more diphosphoglycerate in chronic lung disease, chronic heart disease, and at high altitudes with lower partial pressure of oxygen.

Question 45

Define the Bohr effect in the context of oxygen unloading.

Answer 45

The Bohr effect refers to the phenomenon where an increase in PCO2, a decrease in pH, or an increase in body temperature reduces the affinity of hemoglobin for oxygen, promoting oxygen unloading at peripheral tissues.

Question 46

How does the movement of the oxygen-hemoglobin dissociation curve along the X axis impact oxygen uploading at the lungs?

Answer 46

The movement along the X axis has very little impact on oxygen uploading at the lungs, as it remains on the plateau region of the curve.

Question 47

Describe the impact of factors like pH, PCO2, and body temperature on the relationship between hemoglobin and the partial pressure of oxygen.

Answer 47

These factors can shift the oxygen-hemoglobin dissociation curve, affecting the affinity of hemoglobin for oxygen and influencing oxygen unloading at peripheral tissues.

Question 48

Do lung diseases like emphysema and fibrosis impact alveolar ventilation?

Answer 48

Yes, lung diseases like emphysema can erode surface area, impacting diffusion, while fibrosis can decrease lung compliance, affecting alveolar ventilation.

Question 49

How does diffusion distance impact the process of gas exchange in the lungs?

Answer 49

Diffusion distance, influenced by membrane thickness and interstitial fluid, affects the efficiency of gas exchange in the lungs, with conditions like pulmonary edema and fibrosis illustrating its impact.

Question 50

Describe the role of surface area in gas exchange within the lungs.

Answer 50

Surface area contributes to efficient gas exchange in the lungs, with diseases like emphysema leading to erosion of surface area and impacting gas exchange.

Question 51

Describe the process of carbon dioxide transport in the blood.

Answer 51

Carbon dioxide travels in the blood in the form of carbamino compounds, bicarbonate ions, and dissolved in solution.

Question 52

What is the role of carbonic anhydrase in carbon dioxide transport?

Answer 52

Carbonic anhydrase helps convert carbon dioxide into carbonic acid, which then dissociates into bicarbonate ions and hydrogen ions.

Question 53

How does the chloride shift contribute to carbon dioxide transport?

Answer 53

The chloride shift involves exchanging bicarbonate ions for chloride ions across the red blood cell membrane, allowing bicarbonate ions to travel in the blood.

Question 54

Define carbamino compounds in the context of carbon dioxide transport.

Answer 54

Carbamino compounds refer to the binding of carbon dioxide to deoxyhaemoglobin, with deoxyhaemoglobin being better at forming and buffering these compounds.

Question 55

Describe the reverse process of carbon dioxide transport in the lungs.

Answer 55

In the lungs, haemoglobin releases hydrogen ions, causing bicarbonate to shift back into the red blood cell. Carbonic anhydrase then works in reverse to release carbon dioxide and water.

Question 56

What are the main forms in which carbon dioxide travels in the blood?

Answer 56

Carbon dioxide travels as dissolved carbon dioxide, bicarbonate ions, and carbamino compounds bound to deoxyhaemoglobin.

Question 57

Explain the role of haemoglobin in carbon dioxide transport.

Answer 57

Haemoglobin buffers hydrogen ions released from carbonic acid and associates with carbon dioxide, but prefers to associate with oxygen.

Question 58

Describe the process of gas exchange in the pulmonary circulation.

Answer 58

Oxygenated blood from the pulmonary vein travels to the left side of the heart, then to the systemic circulation, where oxygen is delivered to tissues and carbon dioxide is picked up. Deoxygenated blood returns to the heart and is pumped to the lungs for gas exchange.

Question 59

How do partial pressures of gases in the alveoli and peripheral tissues relate to gas exchange?

Answer 59

The partial pressure in the alveoli reflects the partial pressure in the systemic arterial blood, while the partial pressure in peripheral tissues reflects the partial pressure in venous blood and the pulmonary artery.