Pulmonary Flood Flow, Gas Exchange and Transport 2

Question 1

What volume of oxygen is transported in solution in the plasma?

Answer 1

3ml

Question 2

The presence of haemoglobin increases the carrying capacity of oxygen to what value?

Answer 2

200ml/L

Question 3

How is the bulk of CO2 carried in the blood?

Answer 3

Various forms of solution in plasma and RBC

Question 4

What is the O2 demand of resting tissues?

Answer 4

250ml/min

Question 5

What percentage of arterial O2 is extracted by peripheral tissues at rest?

Answer 5

25%

Question 6

What form of Haemoglobin makes up 92% of all types found in an RBC?

Answer 6

HbA

Question 7

Describe the composition of the 8% of other haemoglobin types

Answer 7

• HbA2 (delta chain replaces beta)

- Glycosylated Hb (HbA1, HbA1b, HbA1c)

Question 8

What factor is the major determinant of the degree to which Hb is saturated with oxygen?

Answer 8

Partial pressure of oxygen

Question 9

How long does it take to saturate an Hb molecule with oxygen? How does this compare to its overall exposure time?

Answer 9

0.25s to saturate

Overall exposure is 0.75s

Plenty of time

Question 10

List three factors which decrease haemoglobin oxygen affinity

Answer 10

• Decrease in pH
• Increase in temp.
• Increase is PCO2

Question 11

Where to the conditions that lead to a decrease in haemoglobin oxygen affinity exist?

Answer 11

Locally in actively metabolising tissues (e.g. muscles) which helps to unload oxygen

Question 12

What conditions cause a rise in haemoglobin oxygen affinity?

Answer 12

• Increase in pH
• Fall in PCO2
• Drop in temp.

Question 13

What molecule can cause haemoglobin oxygen affinity to decrease?

Answer 13

2, 3-diphosphoglycerate (2, 3-DPG)

Question 14

Where is 2, 3-DPG synthesised?

Answer 14

Erythrocytes

Question 15

Where does 2, 3-DPG activity increase?

Answer 15

Associated with areas of inadequate oxygen supply e.g heart or lung disease, living at high altitude etc.

Question 16

What is the overall effect of 2, 3-DPG?

Answer 16

Helps maintain oxygen release in the tissues

Question 17

What occurs to haemoglobin in the presence of carbon monoxide (CO)?

Answer 17

Binds to haemoglobin forming carboxyhemoglobin with an affinity much higher than oxygen

Question 18

What partial pressure of CO is required to cause progressive carboxyhemoglobin formation?

Answer 18

0.4mmHg

Question 19

Why is the respiration rate of a person suffering from CO poisoning normal?

Answer 19

PaCO2 remains normal

Question 20

What are the five main types of hypoxia?

Answer 20

Hypoxic 
Anaemic 
Ischaemic (stagnant)
Histotoxic 
Metabolic

Question 21

What is the most common type of hypoxia?

Answer 21

Hypoxic hypoxia - reduction in oxygen diffusion either due to decreased atmospheric PO2 or tissue pathology

Question 22

What is the cause of anaemic hypoxia?

Answer 22

Reduction in O2 carrying capacity due to anaemia

Question 23

What is ischaemic (stagnant) hypoxia?

Answer 23

Heart disease results in poor pumping of blood

Question 24

What is histotoxic hypoxia?

Answer 24

Poisoning prevents cells using oxygen

Question 25

Give an example of a cause of histotoxic hypoxia

Answer 25

CO or cyanide

Question 26

What is metabolic hypoxia?

Answer 26

Oxygen delivery to the tissues does not reach increased oxygen demand by cells

Question 27

What proportion of CO2 remains dissolved in plasma and erythrocytes?

Answer 27

7%

Question 28

23% of CO2 combines with deoxyhaemoglobin to form what compounds?

Answer 28

Carbamino compounds

Question 29

What is the compound which sequesters most of the CO2 excreted by cells?

Answer 29

70% converted to carbonic acid

Question 30

Describe the fate of carbonic acid in the blood

Answer 30

Dissociates into H+ and bicarbonate ions - the bicarb. is transported into the plasma during the Hamburger Phenomenon to form a buffer and H+ binds to deoxyhaemoglobin to to avoid fucking the pH

Question 31

Why is monitoring plasma [CO2] very important?

Answer 31

It is capable of changing the ECF pH

Question 32

What physiological processes monitor plasma [CO2]?

Answer 32

Hypo/Hyperventilation

Question 33

How does hypoventilation alter plasma [CO2]?

Answer 33

Causes CO2 retardation - plasma [H+] increases - leads to respiratory acidosis

Question 34

How does hyperventilation alter plasma [CO2]?

Answer 34

Blows off more CO2, decreases plasma [H+] - leads to respiratory alkalosis