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Structure & Function 3 > Gas transport and exchange > Flashcards

Gas transport and exchange Flashcards

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1
Q

what is the primary function of the respiratory system?

A

it is to exchange oxygen and carbon dioxide

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2
Q

what three processes are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs?

A

ventilation
diffusion
perfusion

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3
Q

ventilation?

A

it is the process by which air moves in and out of the lungs

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4
Q

what is diffusion?

A

it is the spontaneous movement of gases without the use of any energy or effort by the body, between the gas in the alveoli and the blood in the capillaries in the lungs

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5
Q

what is perfusion?

A

it is the process by which the cardiovascular system pumps blood throughout the lungs

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6
Q

alveoli are sites of?

A

gas exchange

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7
Q

where does inhaled oxygen diffuse?

A

diffuses from the alveoli to the blood in the capillaries

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8
Q

where does carbon dioxide diffuse?

A

it diffuses from the blood in the capillaries to the air in the alveoli

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9
Q

diffusion distance is small (0.7um) so?

A

gas exchange is extensive

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10
Q

pulmonary venous blood will have the same concs of gases as?

A

as alveolar air
it is the process by which the cv system pumps blood throughout the lungs

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11
Q

what is partial pressure?

A

it is the pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own

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12
Q

what are gas partial pressures determined by?

A

by total number of gas molecules per unit volume

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13
Q

where will a gas diffuse from and to?

A

from high to low partial pressure

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14
Q

partial pressures are sometimes displayed in?

A

in kPa

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15
Q

what does solubility of gases depend on?

A

partial pressure of a gas in mixture
chemical properties of gas e.g. CO2 is 20 x more soluble than O2

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16
Q

what are oxygen and carbon dioxide transported in?

A

in an aqueous liquid - the blood

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17
Q

which has the lower partial pressure of oxygen, alveoli/air?

A

alveolar

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18
Q

describe why the partial pressure of oxygen is lower in the alveoli than the air?

A

small proportion of alveolar air exchanged
continuous uptake of O2 into blood
contribution of pH2O (water vapour)

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19
Q

what can alveolar ventilation be determined from?

A

from arterial pO2 and pCO2

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20
Q

optimal gas exchange requires?

A

requires optimum ratio of ventilation (V) to blood flow (Q)

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21
Q

what does V/Q represent?

A

ratio of ventilation to blood flow

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22
Q

V/Q can be different for?

A

for different alveoli

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23
Q

describe V/Q in humans:

A

in humans, the base of the lung has a low V/Q compared to the top

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24
Q

what balances the V/Q across the lungs?

A

deeper breathing in exercise balances V/Q across the lungs

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25
describe the V/Q of quadrupeds?
they have much more uniform V/Q already
26
what is V/Q mismatch?
it is when ventilation or perfusion is altered such that gas exchange is no longer optimal lung disease (reduced V) positional (large animal anaesthesia) (variable V and Q dependent on position) Hypoxic vasoconstriction (reduced Q)
27
why is CO2 exchange less affected by V/Q mismatch?
due to higher diffusion gradient
28
what are the two oxygen carrying proteins?
haemoglobin myoglobin
29
where is haemoglobin found?
in red blood cells in the bloodstream
30
where is myoglobin found?
in vertebrate muscle cells
31
how many oxygens can myoglobin carry?
it has one haem group so can carry one oxygen molecule
32
how many oxygens can myoglobin carry?
each haemoglobin molecules binds up to four oxygen molecules as it has four haem groups each bound oxygen molecule makes the next binding more likely - cooperative
33
each gram of haemoglobin can combine with?
combine with 1.34 mL of O2 and so for a haemoglobin concentration [Hb] of 150g/L blood can contain a maximum of 200mL/L of O2 (O2 capacity)
34
what does the actual amount of O2 bound to haemoglobin (O2 content) depend on?
depends on the pO2 and the percentage O2 saturation = content/capacity x 100
35
describe the left shift of the HbO2 dissociation curve:
high pO2 in the lungs facilitates O2 binding to haemoglobin
36
describe the right shift of the HbO2 dissociation curve:
low pO2 in the tissues facilitates O2 release from haemoglobin
37
what would cause the left shift of the HbO2 dissociation curve?
haemoglobin holds onto O2 more avidly increased pH (metabolic alkalosis) decreased temp decreased pCO2 decreased 2,3-diphosphoglycerate (2,3-DPG) --> (metabolic by-product of glycolysis)
38
what don't bind to 2,3-DPG?
foetal Hb and ruminant Hb don't bind so are left shifted compared to adults or other species
39
what would cause the right shift of the HbO2 dissociation curve?
haemoglobin releases o2 more easily decreased pH (metabolic acidosis) increased temp increased pCO2 increased 2,3-diphosphoglycerate
40
carboxyhaemoglobin?
haem sites bind carbon monoxide 210 times more tightly than o2 cherry red appearance of skin in humans
41
methaemoglobin?
iron in haem groups is Fe3+ normally Fe2+ can be a response to drug toxicity or genetic consequence of paracetamol poisoning in cats
42
what is co2 produced by?
by tissues as by-product of metabolism
43
where does CO2 diffuse along?
along partial pressure gradient from cells to ISF to blood
44
what are the three ways in which carbon dioxide is carried in?
dissolved in plasma (10%) bound to haemoglobin (20%) as bicarbonate (hydrogen carbonate, HC03-) (70%)
45
carbaminohaemoglobin?
carbon dioxide does NOT bind to the haem group (compare with CO) binds instead to amino (NH2) groups within the globin portion binds more easily to deoxyhaemoglobin
46
describe the regulation of ventilation?
breathing is an automatic process depth and frequency can be controlled voluntarily breath holding is possible until pCO2 stimulis overrides
47
what is ventilation controlled by?
by the respiratory centre located within medulla oblongata
48
what is responsible for the rhythm of ventilation?
central pattern generator (Pre-Botzinger complex) and it is influenced by sensory input form CO2, O2 and H+ chemoreceptors
49
where are central chemoreceptors located?
in the medulla oblongata and form synapses with neurones in the respiratory centre
50
exercise results in?
an increase in cellular metabolism which increases o2 demand and co2 production
51
why must cardiac output be higher during exercise?
to increase velocity of blood flow to the capillaries
52
what is erythropoietin a major regulator of?
major regulators of the oxygen-carrying capacity blood
53
acclimatisation factors for high altitude?
increased pulmonary ventilation increased number of RBCs increased vascularity in pulmonary capillaries and increased diffusing capacity of lungs Increased levels of 2,3-DPG increased cellular components
54
how can blood be adapted to function in a low oxygen environment?
higher haemoglobin concs higher haematocrit higher erythrocytic concs of 2,3-DPG lower mean corpuscular haemoglobin concs overall higher Hb but spread over more and smaller cells smaller red blood cells
55
why do most animals have some form of oxygen carrying protein?
in order to increase oxygen carrying capacity
56
what oxygen carrying protein do most vertebrates have?
haemoglobin - gives the red colour
57
how is oxygen transported?
dissolved in plasma
58
cold liquids can carry more?
they can carry more dissolved gas
59
what is 2,3-diphosphoglycerate?
it is a metabolic by-product of glycolysis (increases any time oxygen delivery is insufficient for demand e.g. exercise, higher altitude, anaemia and resp distress)
60
what enzyme do erythrocytes contain?
they have the enzyme carbonic anhydrase
61
where is HCO3- transported for carbon dioxide transport and by what?
it is transported out of erythrocytes by carrier proteins in exchange for Cl-
62
describe the transport of carbon dioxide?
HCO3- is transported out of erythrocyte by carrier protein in exchange for Cl- chloride shift H+ remains inside the cell H+ binds more readily to deoxyHb Facilitates O2 unloading (Bohr effect)
63
holding your breath is possible until?
until partial pressure (pCO2) of co2 stimulus overrides
64
what initiates inspiration?
pacemaker inspiratory neurons initiate inspiration via a series of action potentials
65
after depolarisation, what does the elasticity of the lungs allow for?
allows for expiration
66
what is responsible for forced expiration?
expiratory neurones
67
what is the regulation of ventilation controlled by?
controlled by the resp centre located within medulla oblongata
68
what is the central pattern generator influenced by?
influenced by sensory input from CO2, O2 and H+ chemoreceptors
69

Structure & Function 3 (26 decks)

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