Respiratory L4: Gas exchange and transport

Question 1

Gas exchange at both the pulmonary-capillary and the tissue-capillary levels involves __________ diffusion of O2 and CO2 down partial pressure gradients.

Answer 1

simple passive diffusion

Question 2

What is partial pressure?

Answer 2

weight of gas on its own

Question 3

What is Henry’s Law?

Answer 3

At a given temperature, the amount of a particular gas in solution is directly proportional to the partial pressure of that gas

Question 4

In Henry’s Law, diffusion occurs just based on ________.

Answer 4

partial pressure (gradients)

Question 5

Process of gas exchange and transport: Why is there a decreased partial pressure of oxygen? (160 –> 100). What are the 2 reasons?

Answer 5

1. Humidity of the air (water vapour is added to existing gas) = decrease pressure
2. CO2 out of plasma into alveoli = decrease pressure

• Leave PO2 as 100
• Back to heart to body

Question 6

What is occurring in this diagram? Mention 2 things.

Answer 6

• Has slightly reduced PO2 when starting- due to R and L anatomical shunt
• Back to pulmonary system to be re-oxygenated

Question 7

What are 3 other factors (other than partial pressure) that influences the rate of gas transfer?

Answer 7

1. Surface area
2. Thickness of the membrane (diffusion distance)
3. Diffusion coefficient

Alveoli walls have been destroyed –> increased abnormally large alveoli

Question 8

What are 3 factors that increases the thickness of the membrane?

Answer 8

1. pulmonary oedema
2. pulmonary fibrosis
3. pneumonia

Question 9

What is the diffusion coefficient (D)?

Answer 9

A constant value related to the solubility of a particular gas in the lung tissue and to its molecular weight.

Question 10

The rate of gas transfer is directly ________ to the diffusion coefficient (D), a constant value related to the solubility of a particular gas in the lung tissue and to its molecular weight.

Answer 10

proportional

Question 11

What is the diffusion co-efficent (D) for CO2 compared to O2? Why?

Answer 11

• D for CO2 is 20 times that of O2 because CO2 is much more soluble in body tissues than O2 is.
• The rate of CO2 diffusion across the respiratory membrane is therefore 20 times more rapid than that of O2 .
• The difference in D is offset by the difference in partial pressure. Normally equal amounts of O2 and CO2 are exchanged.

Question 12

What is the gas transport of O2 and CO2 like?

Answer 12

• Only 1.5 % of the O2 in the blood is dissolved; the remaining 98.5% is transported in combination with Haemoglobin (Hb).
• The majority of CO2 is transported in the blood as bicarbonate

Question 13

How is O2 transported in the blood?

Answer 13

transported in combination with Haemoglobin (Hb)

Question 14

How is CO2 transported in the blood?

Answer 14

transported in the blood as bicarbonate

Question 15

What is a heme molecule?

Answer 15

4 max. O2 molecules = full saturated

Question 16

What is the relationship between partial pressure of oxygen in blood and saturation?

Answer 16

Question 17

What is the Bohr Effect? What does shifting right mean? What does shifting left mean?

Answer 17

• Can shift to right or left
  
  • Right = INCREASE body temperature (exercise)
  • Left = DECREASE body temperature
• Shift right = blue
  
  • More offload
  • Less onload
• Eg. normal = 75% Hb saturation at blood PO2 of 40mmHg
• Eg. shift right = 50% Hb saturation at blood PO2 of 40mmHg (offloading more)
• Eg. shift left = higher % Hb saturation at blood PO2 off 400mmHg

Question 18

What is the difference between normal and anemic blood in Hb/100mL?

Answer 18

N > A

15g Hb/100mL > 10g Hb/100mL

Question 19

What is the difference between normal and anemic blood in O2 carrying capacity?

Answer 19

N > A

N

20 ml O2 / 100 ml blood (15 x 1.34 ml O2 / 100ml blood)

A

10 ml O2 / 100 ml blood (7.5 x 1.34 ml O2 / 100ml blood)

Question 20

What is the difference between normal and anemic blood in O2 content of arterial blood?

Answer 20

N > A

N

20 ml O2 / 100 ml blood (Hb saturation with O2 = 100 % at a P O2 = 100mmHg)

A

10 ml O2 / 100 ml blood (Hb saturation with O2 = 100 % at a PO2 = 100mmHg)

Question 21

What is the difference between normal and anemic blood in O2 content of venous blood?

Answer 21

N > A

N

15 ml O2 / 100 ml blood (Hb saturation with O2 = 75 % at a PO2 = 40mmHg)

A

7.5 ml O2 / 100 ml blood (Hb saturation with O2 = 75 % at a PO2 = 40mmHg)

Question 22

Is it beneficial to give oxygen to an anemic patient? If so, why?

Answer 22

• Increased oxygen = increased partial pressure = in plasma (no, have myoglobin is already at at max)
• Full capacity
• To increased saturation limit = train @ increased altitude = increased haemoglobin

Question 23

What is myoglobin?

Answer 23

monomer with one heme

Question 24

What is neuroglobin? What is the function?

Answer 24

is found in neurons.

• The function of this oxygen-binding protein is unknown.

Question 25

Myoglobin (monomer with one heme) stores _______ in _______ muscle and may facilitate diffusion from the blood to the ________.

Answer 25

oxygen; aerobic; mitochondria

Question 26

How is CO2 transported in the plasma?

Answer 26

• 5% dissolved CO2
• 5% CO2+H2O → H2CO3 → HCO3 - + H+
• 1% CO2 + protein → Carbamino compounds

Question 27

How is CO2 transported in the erythrocyte?

Answer 27

• 63% CO2+H2O → H2CO3 → HCO3 - + H+
  
  • H+ + Hb → H.haemoglobin
• 21% CO2+Hb → Carbaminohaemoglobin
• 5% dissolved CO2
• Increased CO2 (in plasma) = respiratory alcoholis- change excitability of muscles- involuntarily contrast

Question 28

What is Davenport’s Diagram?

Answer 28

• Hyperventilate to much
  
  • pH = alkaline
• Don’t breathe enough
  
  • pH = acidic (respiratory alcoholis)

Question 29

In Davenport’s Diagram, if someone hyperventilates to much, how does it impact the blood pH?

Answer 29

pH = alkaline

Question 30

In Davenport’s Diagram, if someone doesn’t breathe enough, how does it impact the blood pH?

Answer 30

pH = acidic (respiratory alcoholis)

Question 31

What is Haldane effect?

Answer 31

After the dissociation of H2CO3, most of the accumulated H+ within the RBCs becomes bound to Hb. As with CO2 , reduced Hb has a greater affinity for H+ than HbO2 does. Therefore, unloading O2 facilitates Hb pickup CO2 -generated H+ . Because only free, dissolved H+ contributes to the acidity of a solution, the venous blood would be considerably more acidic than the arterial blood if Hb did not mop up most of the H+ generated at the tissue level.

• Shift right = more Haldane effect (preventation of blood acidic = prevents H+ and CO3 from forming carbonic acid if left in the blood)
• Normal = only normal Haldane effect
• Shift left = less Haldane effect (less CO2)

Question 32

How do the Bohr effect and Haldane effect work in synchrony?

Answer 32

Bohr effect and Haldane effect work in synchrony to facilitate O2 liberation and the uptake of CO2 and CO2 -generated H+ at the tissue level. Increased CO2 and H+ cause increased O2 release by the Bohr effect; increased O2 release from Hb in turn causes increased CO2 and H+ uptake by Hb through the Haldane effect. The entire process is very efficient. Reduced Hb must be carried back to the lungs to refill on O2 anyway. Meanwhile, after O2 is released, Hb picks up new passengers – CO2 and H+ - that are going in the same direction to the lungs.

Question 33

What are 3 characteristics when someone go deep-sea diving?

Answer 33

1. Nitrogen narcosis (“raptures of the deep”) is believed to result from a reduction in the excitability of neurons because of the highly lipid-soluble N2.
2. High-pressure neurological syndrome (HPNS) occurs below 200m. Mounting pressure results in tremors and convulsion.
3. Decompression sickness (“the bends”) occurs during sudden ascent to the surface, the rapid reduction in pressure causes N2 to quickly come out of solution and form bubbles of gaseous N2 in the body, particularly in joints.

Question 34

What are 5 adaptation of deep-diving mammals?

Answer 34

1. Elimination of blood flow to most organs, except heart, brain and adrenal gland
2. Reduction of body temperature by up to 3°C
3. Bradycardia (2-6 beats/min)
4. Exhalation before dive, reduces buoyancy
5. Smaller lungs with special airways to store remaining gases after the lungs collapse below 40m that prevent the gases to enter the circulation

Question 35

What are 4 things that could occur when there is a sudden decompression of an aircraft cabin at 9000m altitude?

Answer 35

1. Oxygen is less than 30% of that at sea level.
2. Drastically reduced Hb saturation with O2 .
3. O2 deprivation of the brain results in unconsciousness.
4. Death from hypoxia

Question 36

What are 3 adaptation of high-fliers (eg. the bar-headed goose, who can reach an altitude of 9000m)?

Answer 36

1. A very low P50 of 10mmHg!
2. Counter-current perfused flow through lungs
3. Increased Myoglobin?