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BIOM20002 - HSF > Lecture 59 - Gas Exchange and Transport > Flashcards

Lecture 59 - Gas Exchange and Transport Flashcards

1
Q

How much is 1 atm?

A

760 mmHg

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2
Q

Describe relative gas concentrations in the air

A

Nitrogen: high partial pressure
Oxygen: 160 mmHg
CO2: very low partial pressure

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3
Q

What is the difference between reidual and reserve volume?

A

Residual: can never be expirated
Reserve: amount that can be exhaled

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4
Q

Why have a residual volume?

A
  • decreases energy required to reinflate lungs

- lung would not remain open

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5
Q

What happens to dead space during exercise?

A

nothing

Remains the same

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6
Q

Describe the features of the alveoli that make it good for gas exchange

A
  • large surface area

- very thin wall to diffuse across

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7
Q

Describe the structures that oxygen moves across to get into the blood

A

One cell thick alveolar epithelium

Fused basement membrane

Endothelial cell

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8
Q

How does Fick’s law relate to alveolar structure?

A

Fick’s law of diffusion says;

  • increased surface area
  • decreased thickness
  • greater pressure gradient

will lead to greater rate of diffusion of oxygen across the alveoli

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9
Q

Describe how concentration of gases in the atmosphere changes with altitude

A

The concentration does vary very much

It is the partial pressures of the gases that changes

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10
Q

Which variables can be altered to increase rate of diffusion of oxygen into the blood?

A

Concentration of oxygen in the breathed air

eg in Anaesthesia
65% oxygen in air

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11
Q

Describe what happens to the partial pressure of oxygen when air moves from the atmosphere into the alveoli
Why?

A

Partial pressure drops; 160 –> 100 mmHg

  • mixing with old air with depleted oxygen
  • air is moistened by mucous membrane
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12
Q

Compare the differences in PO2 in oxygenated and deoxygenated blood

A

Oxygenated: 100 mmHg
Deoxygenated: 40 mmHg

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13
Q

What happens to oxygen when we climb up higher than 5 km?

A

PO2 drops to 80 mmHg

Less oxygen is getting into the blood

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14
Q

Describe gases dissolving into liquids

A

When a liquid is exposed to a gas at a given pressure, the gas will move into solution until…

Partial pressure of gas is the same in the liquid and in the air.

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15
Q

How does solubility affect dissolution of gases into liquids?

A

Greater solubility:

  • greater concentration of the gas in the liquid once equilibrium is reached
    eg. CO2

Lesser solubility:
- lesser concentration of gas in the liquid once equilibrium is reached
eg O2

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16
Q

At equilibrium, will the concentration of the gas in the liquid and in the air be the same?

A

No

This depends on solubility of the gas

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17
Q

Is O2 or CO2 more soluble?

A

CO2

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18
Q

Describe how oxygen is transported in the blood

A
  1. O2 diffuses through cells into plasma

2. Combines chemically with haemoglobin (Hb)

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19
Q

Why must oxygen combine with Hb in the blood?

A

Because O2 is very insoluble

Hb increases the oxygen carrying capacity of the blood

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20
Q

How much Hb is present in the body?

A

Males: 15g / 100 ml
Females: 13g / 100 ml

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21
Q

What is the concentration of oxygen in the blood?

A

173 ml / L of blood

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22
Q

What is VO2 max?

A

The maximum amount of oxygen that can be taken up from the environment per unit time

23
Q

What measurement is a good measure of fitness?

A

VO2 max

ie amount of oxygen that can be carried

24
Q

How can VO2 max be increased?

A

EPO

25
Q

Describe the O2-Hb dissociation curve

What does this mean?

A

Non-linear relationship between PO2 and binding

At alveoli:
considerable decrease in PO2, binding not much affected

At metabolically active cells:
- PO2 drops right down, binding decreases and O2 offloaded

26
Q

What happens to O2 levels in the blood during exercise?

A

Drops to 25 mmHg

27
Q

Describe the Bohr effect

A

Increase of O2 off-loading when needed

28
Q

Under which conditions is increased off-loading of O2 seen?

A
  • acidity
  • increase in temperature
  • high CO2
29
Q

What is DPG?

What is its effect on Hb binding?

A

An intermediate of anaerobic metabolism
Di-phospho glycerate

Shifts the curve to the right –> increased O2 offloading

30
Q

Under what conditions does DPG increase?

A

Hypoxia
Altitude
Anaemia

31
Q

Describe the ways that oxygen is transported in the blood

A

1/ Bound to Hb

2/ Dissolved in the blood ( 1.5 %)

32
Q

Describe how CO2 is transported in the blood

A

1/ in solution: 7%
2/ Bound to Hb: 23%
3/ As bicarbonate: 70%

33
Q

What is the name for Hb carrying CO2?

A

Carbamino haemoglobin

34
Q

Compare partial pressure of CO2 in alveoli and in blood

A

Aleoli: 40 mmHg
Blood: 46 mmHg

35
Q

Describe the formation of bicarbonate

A

CO2 + H2O –> H2CO3 carbonic acid

under carbonic anhydrase (CA)

36
Q

What is H2CO3?

A

Carbonic acid

37
Q

Where is CO2 converted to carbonic acid?

A

In red blood cells

38
Q

What happens after carbonic acid is formed by carbonic anhydrase?

A

Ionises to form bicarbonate

39
Q

Is the carbonic anhydrase reaction favoured in the tissues?

A

Yes

Because there is much CO2 present because it is being made by the respiring cells

40
Q

Describe what happens to bicarbonate in the lungs

A

Reaction is reversed
CO2 reforms
Diffuses out into the alveoli

41
Q

When is carbamino Hb formation favoured?

Why?

When is carbamino Hb formation disfavoured?

A

At the tissues
Due to reduced Hb-oxygen affinity due to the Bohr effect

Carbamino Hb formation reversed at the lungs
(ie CO2 is kicked off)

42
Q

What is the Haldane effect?

A

In low O2 environment, Hb has increased affinity for CO2

43
Q

Compare grossly control of gas transport and control of respiration

A

Respiration: neurally controlled

Gas transport: passive

44
Q

What are the effects of hyperventilation?

Why?

A
  • increased ventilation
  • decreased PCO2 in arteries
  • increased PO2 in arteries
  • decreased PCO2 in veins
  • increased PO2 in veins
  • increased alkalosis
  • decreased respiratory drive

(more fresh air
Residual capacity being turned over more regularly

45
Q

What is alkalosis?

A

Less carbonic acid in the blood

ie blood is more basic

46
Q

What happens to PO2 in the arteries during hyperventilation?

A

Increases

47
Q

What does decreased respiratory drive mean?

A

Breath can be held for longer

48
Q

What happens to PCO2 in veins during hyperventilation?

A

Decreases

49
Q

What are the effects of hypoventilation?

A
  • Increased PCO2 in arteries
  • Decreased PO2 in arteries
  • Increased PCO2 in veins
  • Decreased PO2 in veins
  • increased acidosis
  • increased respiratory drive
50
Q

What is acidosis?

A

Increased carbonic acid in the blood

ie blood is more acidic

51
Q

What happens to PO2 in arteries during moderate exercise?

A

Stays the same

Coming from the lungs, which is still oxygenating it to the same degree

52
Q

What happens to PO2 in veins during moderate exercise?

A

Decreases

  • Muscles consuming more
  • increased ventilation
53
Q

Which process does PCO2 control?

A

Ventilation

BIOM20002 - HSF (60 decks)

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