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BMS12 > Respiration 2 > Flashcards

Respiration 2 Flashcards

1
Q

What are the fractional concentrations of different gases in dry air?

A

Nitrogen and inert gases = 0.79 (79%)

Oxygen = 0.21 (21%)

Carbon dioxide = 0.0004 (0.04%)

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2
Q

Why do the fractional concentrations of gases change in humid air?

A

Water vapour present

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3
Q

At rest, how much oxygen is consumed by tissues and how much carbon dioxide is produced per minute?

A

250ml oxygen

200ml carbon dioxide

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4
Q

Why is the amount of oxygen used by tissues not equal to the amount of carbon dioxide produced?

A

Oxidation of organic fuel produces water as well

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5
Q

What is the respiratory quotient?

A

0.8

Carbon dioxide produced/oxygen consumed

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6
Q

What is alveolar ventilation at rest?

A

~4200ml/min

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7
Q

Describe the volumes of oxygen transported around the body per minute.

A

250ml absorbed into blood from alveoli

Added to a 750ml reservoir

250ml used by cells

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8
Q

How much oxygen is inhaled (into alveoli) and exhaled per minute (with calculations)?

A

0.21 x 4200 = 882ml inhaled into alveoli per min

882 - 250 = 632ml exhaled from alveoli per min

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9
Q

What are the volumes of carbon dioxide being transported around the body per minute?

A

Tissues produce 200ml

Added to 2400ml reservoir

200ml expired

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10
Q

What is the pressure exerted by a gas proportional to?

A

Temperature + number of gas molecules in a given volume

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11
Q

What is Dalton’s law regarding pressure?

A

Individual pressure of a particular gas in a mixture of chemically inert gases is called the partial pressure

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12
Q

What is the total pressure of a mixture of inert gases equal to?

A

Sum of all the partial pressures

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13
Q

Describe how the partial pressure of oxygen changes through a breath.

A

21% in atmospheric air

Diluted by water vapour in upper airways

Absorbed into blood at alveoli (13.3) so decreases

Alveolar gas mixes with fresh air of anatomical dead space so increases

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14
Q

Describe how the partial pressure of carbon dioxide changes through a breath.

A

Virtually 0 until gas exchange in alveoli (5.3)

Alveolar gas mixes with fresh air of anatomical dead space dilutes carbon dioxide

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15
Q

Describe how the partial pressure of water vapour changes through a breath.

A

Variable in atmospheric air

Increases due to humidification in upper airways (6.3kPa)

Alveolar gas mixes with fresh air of anatomical dead space (variable)

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16
Q

What is Henry’s law regarding dissolved gases?

A

Amount of gas dissolved in a liquid ∝ partial pressure of that gas in equilibrium with that liquid

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17
Q

How does a gas diffuse?

A

From high to low partial pressures

Independent of other gases

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18
Q

For an air-fluid system in equilibrium, how are the partial pressures related?

A

Air pp = fluid pp

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19
Q

Why do we use partial pressures over concentrations of gases?

A

Easier to measure

Gives a better idea of movement

Concentration depends on solubility as well as pp

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20
Q

What is the equation linking concentration, solubility and partial pressure?

A

Concentration = solubility x partial pressure

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21
Q

How do systemic blood and alveolar partial pressures of oxygen change during gaseous exchange?

A

Systemic blood pp equilibrates to almost match alveolar pp

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22
Q

How do blood and alveolar partial pressures of carbon dioxide change after gaseous exchange?

A

Alveolar pp equilibrates to exactly match blood pp

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23
Q

What determines the rate of gaseous transfer (factors or equation)?

A

Partial pressure difference (P1 - P2)

Solubility of a gas in the fluid at 37°C

Diffusion barrier (SA/thickness)

Rate = (SA/thickness) x (P1 - P2) x S x (1/√mW)

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24
Q

What is the partial pressure gradient of oxygen during gas exchange?

A

13.3 - 5.3 = 8kPa into blood

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25
Q

How is the rate of gaseous exchange of oxygen limited?

A

Low solubility of oxygen in arterial blood

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26
Q

What is the partial pressure gradient of carbon dioxide during gas exchange?

A

5.3 - 6.1 = (-)0.8kPa out of blood

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27
Q

How efficient is gas exchange in the alveoli at rest?

A

Equilibrium is reached only one-third of the way along a pulmonary capillary

28
Q

What are the partial pressures in blood straight after gas exchange?

A

Oxygen = 13.3kPa

Carbon dioxide = 5.3kPa

29
Q

Why is the partial pressure of oxygen in systemic blood not 13.3kPa?

A

Anatomical left to right shunt (bronchial)

Drainage of part of coronary venous blood directly into left ventricle

30
Q

What is the anatomical left to right shunt?

A

Deoxygenated bronchial vein blood mixes with and dilutes oxygenated pulmonary vein blood

31
Q

How much of the cardiac output is deoxygenated?

A

~2%

32
Q

What must the capillary partial pressure of oxygen be sufficiently high enough for?

A

To maintain partial pressure gradient to supply mitochondria

33
Q

What is the partial pressure of oxygen in the mitochondria?

A

0.13kPa

34
Q

How does gaseous transfer differ between alveoli and tissues?

A

Opposite direction of movement

Transfer occurs along the whole capillary in tissues but in alveoli reaches equilibrium one-third along

35
Q

What is 1dl in ml?

A

100ml

36
Q

What is the solubility of oxygen and carbon dioxide in arterial blood?

A
  1. 3ml/dl oxygen (in 13.3kPa pp)

2. 74ml/dl carbon dioxide (in 5.3kPa pp)

37
Q

What are the four important measures in oxygen transport?

A

Percent saturation

Oxygen content

Maximum oxygen carrying capacity

Partial pressure

38
Q

What is percentage saturation of oxygen?

A

Percentage of oxygen-binding sites on Hb that are bound to oxygen

39
Q

What is oxygen content (ml/dl)?

A

Amount of gas present in blood = amount bound to Hb + amount dissolved in plasma

40
Q

What is the maximum oxygen carrying capacity?

A

Amount of oxygen blood is capable of carrying when Hb is 100% saturated

41
Q

What is the main determinant of amount of oxygen dissolved in the plasma and of percentage saturation?

A

Partial pressure of oxygen

42
Q

What percentage of the oxygen content is carried by Hb?

A

98.5%

43
Q

Why do we need haemoglobin?

A

Greatly increases amount of oxygen which can be carried by blood

Oxygen solubility is low

44
Q

What is the percentage saturation and oxygen content of blood entering pulmonary capillaries?

A

75% saturated

15ml/dl

45
Q

Calculate the rate of oxygen circulation through the body per minute.

A

5L/min x 200ml/L = 1000ml/min

Cardiac output x oxygen content

46
Q

Describe the structure of haemoglobin.

A

Quaternary structure protein

2 α-chains and 2 β-chains each with its own haem group

Haem group contains a ferrous Fe2+ ion

47
Q

What does the haem group bind to?

A

Histidine of globin molecule

1 molecule of oxygen

48
Q

Why is the loading of oxygen onto haemoglobin referred to as oxygenation rather than oxidation?

A

Fe2+ remains in ferrous state

49
Q

What is cooperative binding of haemoglobin?

A

Binding of one oxygen molecule increases the affinity of the remaining sites for oxygen

50
Q

What causes the sigmoidal shape of the oxygen dissociation curve?

A

Cooperative binding

51
Q

How much haemoglobin is in the blood normally?

A

15g/dl

52
Q

What is the benefit of the exponential phase of the oxygen dissociation curve?

A

Oxygen consumption in tissues lowers pp

Large drops in percentage saturation with small drops in pp aids unloading of oxygen where needed

53
Q

What is the benefit of the plateau phase of the oxygen dissociation curve?

A

Large drops in pp cause only a small decrease in percentage saturation

Supports oxygen uptake at low atmospheric pp or in respiratory disease

54
Q

Describe the shift of the oxygen dissociation curve in the lungs and the factors affecting uptake.

A

Leftward shift (aids uptake)

Loss of carbon dioxide = increased pH

Evaporation lowers temperature

Decreased [2,3-diphosphoglycerate]

55
Q

Describe the shift of the oxygen dissociation curve in the tissues and the factors affecting uptake.

A

Rightward shift (aids unloading)

Carbon dioxide produced = decreased pH

Metabolism raises temperature

Increased [2,3-diphosphoglycerate]

56
Q

How can carbon dioxide be transported in the blood?

A

Dissolved

Bicarbonate

Carbamino compounds

57
Q

Where is the carbon dioxide carried as bicarbonate found?

A

Dissolved in blood

In erythrocytes

58
Q

Describe the processes of RBC carrying bicarbonate.

A

Carbonic anhydrase accelerates conversion to bicarbonate

H+ produced are buffered by Hb - Haldane effect A

HCO3- exchanged for Cl-/chloride shift

59
Q

How is carbon dioxide carried as carbamino compounds?

A

In erythrocytes, carbon dioxide reacts with amino groups of lysine and arginine residues of Hb - Haldane effect B

60
Q

What is the Haldane effect A?

A

H+ produced in erythrocytes are buffered by Hb

61
Q

What is the Haldane effect B?

A

In erythrocytes, carbon dioxide reacts with amino groups of lysine and arginine residues of Hb

62
Q

In what form does haemoglobin form carbamino compounds more readily and what is the benefit of this?

A

Deoxy-Hb

Removal of carbon dioxide at tissues

63
Q

How is the majority of carbon dioxide carried in blood?

A

As bicarbonate

64
Q

Describe the carbon dioxide dissociation curves.

A

Semi-linear over physiological pCO2

Greater amount of carbon dioxide carried by deoxygenated blood than oxygenated at any given pp (Haldane effect)

65
Q

What are the values for carbon dioxide in arterial and venous blood?

A

Arterial = 48ml/dl, 5.3kPa

Venous = 52ml/dl, 6.1kPa

66
Q

What are the values for oxygen in arterial and venous blood?

A

Arterial = 20ml/dl, 12.5kPa

Venous = 15ml/dl, 5.3kPa

BMS12 (7 decks)

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