Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cardiovascular And Respiratory System > Blood-gas Transport > Flashcards

Blood-gas Transport Flashcards

1
Q

What is the average figure for oxygen consumption ?

A

250 ml/minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the average figure for carbon dioxide production ?

A

200 ml/minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is meant by partial pressure ?

A

Partial pressure of a gas is a measure of the concentration of a gas in a mixture of gases dissolved in the blood
- measured in mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the partial pressure of oxygen and carbon dioxide in the alveoli and the body cells

A
  • partial pressure of oxygen is higher in the alveoli compared to the tissue
  • partial pressure of carbon dioxide is higher in the tissue compared to the alveoli although the pressure gradient isn’t too steep
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe Fick’s law of diffusion

A

The diffusion rate of a gas through a sheet of tissue also depends on the surface area and thickness of the membrane through which it is diffusing
e.g. the alveoli have a large surface area and the capillaries have very thin walls so increased rate of diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe how a partial pressure gradient influences gas transfer rates

A
  • rate of transfer increases as partial pressure gradient increases
  • this is the major determinant in the rate of transfer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe how alveolar surface area influences gas transfer rates

A
  • rate of transfer increases as surface area increases
  • alveolar surface area remains constant under resting conditions
  • alveolar surface area increases during exercise and this increases the rate of breathing
    (exercise also causes vasodilation of capillaries so this increases surface area aswell)
  • alveolar surface area decreases with pathological conditions such as emphysema and COPD
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe how membrane thickness influences gas transfer rates

A
  • rate of transfer decreases as thickness increases
  • thickness is normally constant but it can increase with pathological conditions such as pulmonary oedema
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe how oxygen is carried to tissues

A
  • it is bound to haemoglobin (98.5%)
  • it is physically dissolved in the blood (1.5%)
  • the amount dissolved in the blood is proportional to the partial pressure of oxygen in the blood
  • oxygen bound to haemoglobin does not contribute to partial pressure of oxygen in the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the structure of erythrocytes

A
  • flat and disc shaped cells indented in the middle - biconcave disk (increases surface area)
  • no nucleus
  • no mitochondria or other organelles
  • 2 micrometers thick
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How many red blood cells does 1ml of blood contain ?

A

~ 5 billion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is meant by haematocrit ?

A

The percentage of blood composed of red blood cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the average haematocrit of the blood ?

A

~ 45%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the key features of red blood cells ?

A
  • large surface area for diffusion
  • thinness of the cell enables oxygen to diffuse rapidly
  • they are very flexible to fit through narrow capillaries
  • contain several hundred haemoglobin molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the structure of haemoglobin

A
  • only found in red blood cells
  • made of 2 parts :
    1) the globin portion is made of 4 highly folded polypeptide chains (2 alpha and 2 beta)
    2) 4 iron containing non protein groups known as haem groups
  • each haem group is bound to one of the polypeptide chains
  • oxygen binds to the haem group
  • each iron atom can bind one molecule of oxygen so 4 altogether
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why can haemoglobin appear as slightly different colours ?

A
  • it is a naturally coloured pigment
  • because of the iron it can appear reddish in arterial blood when combined with oxygen and bluish in venous blood when deoxygenated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is oxyhaemoglobin ?

A

Oxygen bound to haemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What can haemoglobin carry ?

A
  • carbon dioxide
  • hydrogen ions
  • carbon monoxide
  • nitric oxide (NO)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Summarise the function of nitric oxide

A
  • nitric oxide is a vasodilator
  • in the lungs NO binds to haemoglobin
  • it is released at the tissues where it relaxes and dilates arterioles
  • it has a blood pressure stabilising effect
20
Q

What is deoxyhaemoglobin ?

A
  • reduced haemoglobin
  • lost one or more of its oxygen molecules
  • when haemoglobin loses most of its oxygen it becomes bluish in colour
  • if the quantity of deoxyhaemoglobin in the blood exceeds 5 g/dl it is known as cyanosis
21
Q

What shape is the haemoglobin dissociation curve ?

A

sigmoidal shape

22
Q

What is the normal partial pressure of oxygen at the pulmonary capillaries ?

A

60 - 100 mmHg
- at these higher partial pressures there is smaller changes in haemoglobin saturation
- haemoglobin is 97.5 % saturated

23
Q

What is the average resting partial pressure of oxygen at the systemic capillaries ?

A

20 - 60 mmHg
- there are larger changes in haemoglobin saturation
- haemoglobin is 75% saturated

24
Q

What is the typical partial pressures of oxygen in the tissue capillaries during strenuous exercise ?

A

20 mmHg

25
Q

Describe the delivery of oxygen to the tissues in relation to haemoglobin

A
  • the partial pressure of oxygen is different at the lungs and tissues and so :
    • haemoglobin loads up on oxygen at the lungs where the partial pressure of oxygen is higher
    • haemoglobin unloads oxygen in the tissues where partial pressure of oxygen is lower
26
Q

If the partial pressure of oxygen is doubled does the haemoglobin saturation double ?

A

Doubling the partial pressure of oxygen does not double the percentage of haemoglobin saturation because the relationship between partial pressure of oxygen and haemoglobin saturation is not linear but rather sigmoidal

27
Q

Summarise anaemia

A

Anaemia is the reduction in red blood cells and/or haemoglobin
- the red blood cells carry insufficient oxygen
- haemoglobin saturation and partial pressure of oxygen are normal in anaemia but the ability to carry as much oxygen is reduced

28
Q

What is the Bohr shift ?

A

A shift in the haemoglobin dissociation curve caused by changes in pH and the influence of carbon dioxide

29
Q

Which factors cause the curve to shift to the left ?

A
  • increase in pH
  • decrease in temperature
  • decrease in partial pressure of carbon dioxide
  • decrease in 2-3 BPG
30
Q

Which factors cause the curve to shift to the right ?

A
  • decrease in pH
  • increase in temperature
  • increase in partial pressure of carbon dioxide
  • increase in 2-3 BPG
31
Q

If the curve shifts to the left what does this indicate ?

A
  • less oxygen is released at the tissues
  • higher percentage saturation at lower oxygen partial pressures
32
Q

If the curve shifts to the right what does this indicate ?

A
  • more oxygen is released at the tissues
  • lower percentage saturation at higher oxygen partial pressures
33
Q

Why does the Bohr effect cause the dissociation curve to shift right in acidic environments ?

A
  • an increase in hydrogen ion concentration and a decrease in pH
  • loss of bicarbonate ions
  • hydrogen ions can bind to haemoglobin which reduces the affinity between oxygen and haemoglobin
  • oxygen is released to the tissues
34
Q

What effect will an increase in partial pressure of carbon dioxide have on the dissociation curve ?

A
  • it will shift right
  • increase in PCO2 = increase in hydrogen ions
  • carbon dioxide and hydrogen ions can bind to haemoglobin reducing the affinity between oxygen and Hb
  • oxygen is released to the tissues
35
Q

Describe the Bohr effect

A
  • both hydrogen ions and carbon dioxide can combine reversibly with haemoglobin
  • this causes a structural change to haemoglobin
  • haemoglobin now has a decreased affinity for oxygen
  • oxygen is released from haemoglobin
  • increased delivery of oxygen to the tissues
36
Q

Describe the effect of temperature on the dissociation curve

A

Increase in temperature:
- oxygen is released to the tissues
- shifts right

Decrease in temperature:
- shifts left

37
Q

Describe the effect of 2,3-BPG on the dissociation curve

A

An increase in 2,3-BPG -
• produced inside red blood cells during glycolysis
• occurs when arterial oxyhaemoglobin is below normal
• 2,3-BPG binds reversibly to haemoglobin
• this reduces haemoglobin’s affinity for oxygen
• oxygen is released to the tissues
• curve shifts to the right

38
Q

Describe the structure and function of foetal haemoglobin

A
  • has 2 gamma protein chains instead of 2 beta chains
  • the gamma chains enhance haemoglobin oxygen binding in low oxygen environments
  • oxygen released by maternal haemoglobin is bound by the higher affinity HbF
  • HbF curve is to the left of HbA
39
Q

Summarise the relationship between carbon monoxide and haemoglobin saturation

A
  • carbon monoxide and oxygen compete for the same binding sites on haemoglobin
  • haemoglobin’s affinity for CO is 240x that of oxygen
  • haemoglobin is no longer able to transport oxygen
  • normal blood partial pressure of oxygen and haemoglobin level remain normal but oxygen content of blood is seriously reduced
40
Q

Describe how carbon dioxide is carried to tissues

A
  • 60-70% as bicarbonate ions
  • 20-30% bound to haemoglobin
  • 5-10% physically dissolved in the blood
41
Q

Describe how carbon dioxide is transported by binding to haemoglobin

A
  • 20-30% of carbon dioxide binds to haemoglobin
  • forms carbamino-haemoglobin
  • carbon dioxide binds with the globin portion of haemoglobin
42
Q

Describe how carbon dioxide is transported as bicarbonate ions

A
  • 60-70% is transported as bicarbonate ions
  • bicarbonate ions are more soluble in blood than carbon dioxide
  • this reaction proceeds very slowly in the plasma but very swiftly in red blood cells due to the carbonic anhydrase enzyme

CO2 + H2O > H+ + HCO3 -

43
Q

Describe the chloride shift

A
  • the red blood cell membrane is relatively impermeable to hydrogen ions
  • there is a HCO3/Cl- carrier in the membrane that allows bicarbonate ions diffuse down its concentration gradient
  • bicarbonate ions diffuse out of the red blood cell into the plasma
  • chloride ions diffuse down their concentration gradient into the red blood cells to maintain an electrical gradient
44
Q

What is the Haldane effect ?

A
  • haemoglobin binds most of the hydrogen ions and some of the carbon dioxide formed within the red blood cells
  • removing oxygen from the haemoglobin increases the ability of haemoglobin to pick up carbon dioxide and carbon dioxide generated hydrogen ions
  • this enhances the oxygen release from haemoglobin
  • this is known as the Haldane effect
45
Q

What is the difference between the Bohr effect and the Haldane effect ?

A
  • the Haldane effect describes how oxygen concentrations determine haemoglobin’s affinity for carbon dioxide
  • the Bohr effect describes how carbon dioxide and hydrogen ions affect the affinity of haemoglobin for oxygen

Cardiovascular And Respiratory System (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions