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Exercise Physiology 2230 > LESSON 17 - diffusive oxygen transport into muscle > Flashcards

LESSON 17 - diffusive oxygen transport into muscle Flashcards

1
Q

how does O2 transport from blood to muscle ?

A
  • dissociation of O2 from hemoglobin
  • when the red blood cells pass single file through the tiny capillaries that surround muscle cells
  • oxygen molecules are released from hemoglobin and diffuse into the muscle cells
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2
Q

what is O2 utilization in the mitochondria ?

A

Krebs cycle and ETC (helps with proton balance)

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3
Q

“O2 drives the flow of electrons along the electron transport chain which facilitates proton pumping and establishes the electrochemical gradient necessary to drive ATP synthase” :

A
  1. O2 is drawn to complex 4 where it accepts electron pairs
  2. the reduced form of O2 then combines with a pair of electrons to form H20
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4
Q

describe the flow of O2 :

A

blood plasma → capillary endothelium → interstitial space → sarcoplasm → mitochondria → complex 4

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5
Q

what are the two ways we deliver O2 ?

A

convection and diffusion

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6
Q

what is convection ?

A

transfer of O2 by movement of RBC within arterial blood to the tissue

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7
Q

what is diffusion ?

A

transfer of O2 from an area of high pressure (arterial blood0 to low pressure (tissue)

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8
Q

does diffusion take energy ?

A

no

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9
Q

what is the term used for movement due to a fluid ?

A

convection

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10
Q

why do we need convection ?

A

we need for blood to be moved around

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11
Q

describe diffusion within the lungs :

A

O2 diffuses from alveoli into the pulmonary capillaries

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12
Q

describe diffusion within the tissues :

A

O2 diffuses from the systemic capillaries into the skeletal muscle mitochondria

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13
Q

what is diffusion within the lungs driven by ?

A

the gradient between the partial pressure of O2 in the alveolar space and that in the deoxygenated pulmonary capillary blood

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14
Q

describe capillary concentration with diffusion in lungs :

A

low concentration in capillaries

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15
Q

what is diffusion within the tissues driven by ?

A

the gradient between the partial pressure of O2 in muscle capillaries and that of the mitochondria

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16
Q

describe capillary concentration with diffusion within the tissues :

A

high concentration in tissues pushing to where’s low

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17
Q

what is the formula for convection ?

A

VO2 = Q x a-vO2 difference

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18
Q

diffusive O2 delivery is a how many step process ?

A

2

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19
Q

describe the diffusive two step process :

A
  1. diffusion of O2 from blood to sarcoplasm (cytosol)
  2. diffusion of O2 from sarcoplasm to mitochondria
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20
Q

as RBCs pass single file through the tiny capillaries that surround muscle cells, where is O2 released from ?

A

released from Hb (where it can then diffuse into the muscle cells)

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21
Q

when oxygenated blood reaches muscle cells, what happens between the blond of O2 and Hb molecules ?

A

the bond between O2 and Hb molecules weakens

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22
Q

what does Hb stand for ?

A

hemoglobin

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23
Q

where is capillary PO2 within the partial pressure and HbO2 oxygen transport cascade ?

A

between mean capillary (40) and myoglobin (2-3)

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24
Q

why does arterial PO2 fall by so much once it enters the capillary ?

A

arterial PO2 falls in capillaries because oxygen is released from hemoglobin to supply surrounding tissues with the oxygen they need for energy production.

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25
Q

when oxygenated blood reaches muscle cells, what happens to bonds between O2 and Hb. why?

A

the bonds weaken or loosen.

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26
Q

why do the bonds of O2 and Hb weaken/loosen ?

A

because the muscle cells have a higher demand for oxygen during activity. The decrease in oxygen concentration near the muscle cells prompts hemoglobin to release oxygen, facilitating its delivery to the cells for energy production through cellular respiration.

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27
Q

why is mixed venous PO2 (20mmHg) lower than mean capillary PO2 (40mmHg) ?

A

because tissues extract oxygen from the blood in capillaries, leaving lower oxygen levels in the venous blood returning to the heart.

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28
Q

FILL IN THE BLANK

“as a plug of blood first enters the capillary, _________ diffuses out of the plasma, lowering its PO2”

A

dissolved O2

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29
Q

what does the lowering of capillary PO2 help facilitate in ?

A

facilitates off-loading of O2 from Hb in RBCs

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30
Q

what does it mean “the further along the capillary” ?

A

nearest the venule

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31
Q

FILL IN THE BLANK

the further along the capillary, the more and more __ leaves this the plasma causes an exponential-like fall in capillary PO2 ?

A

O2

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32
Q

the nearer to the venule the capillaries, what does the mean for O2 ?

A

the more and more O2 leaves the plasma

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33
Q

what is more released during exercise / at high intensities ?

A

CO2

34
Q

where is CO2 being released from during exercise/at high intensities ?

A

at the tissues

35
Q

when more and more CO2 is released from the tissue… what does this do ?

A

increases capillary PCO2 towards the venular end

36
Q

FILL IN THE BLANK

in regards to PO2 of arterioles, capillaries and veins “end-capillary” PO2 may be ________- relative to “mean-capillary”

A

quite low

37
Q

what happens to the rate of mitochondria ATP synthesis when PO2 continues to fall ?

A

becomes limited

38
Q

how many forms of O2 diffusion into the mitochondria are there ?

A

2

39
Q

what are the two O2 diffusion into mitochondria ?

A
  1. dissolves O2
  2. myoglobin-facilitated O2 diffusion
40
Q

what is myoglobin ?

A

an iron containing globular protein in skeletal and cardiac muscle fibers

41
Q

what does myoglobin provide ?

A

an “extra” O2 store to release O2 at low PO2

42
Q

when do we use myoglobin ?

A

for O2 diffusion from blood to sarcoplasm

43
Q

what does myoglobin resemble ?

A

resembles Hb because it also combines reversible with O2

44
Q

how does myoglobin differ from Hb ?

A

because each Mb molecule contains only 1 iron atom compared to 4

45
Q

what does Mb stand for ?

A

myoglobin

46
Q

during diffusion of O2 from blood to sarcoplasm, in capillaries what can Hb do ?

A

Hb can hand off O2 to a Mb inside the muscle cell in the following chemical reaction : Mb + O2 = MbO2

47
Q

describe stauration in myoglobin ?

A

saturation always really high

48
Q

is the Mb curve vs Hb similar or different ?

A

very different

49
Q

why is the Mb curve so different from the Hb one ?

A

because it much more readily binds and retains O2 at low PO2

50
Q

is myoglobin affinity for O2 dependent on other variables ? (shifting, curving, etc.)

A

no, it is not dependent on other variables

51
Q

what does diffusive O2 delivery mean ?

A

ability of the muscle to extract O2 from blood to muscle mitochondria

52
Q

where is myoglobin found ?

A

found exclusively in heart and skeletal muscle cells

53
Q

what is the cell the holds the myoglobin ?

A

myocyte / mitochondrion

54
Q

how many muscle diffusion capacity are there ?

A

3

55
Q

what are the three muscle diffusion capacities ?

A
  1. pressure gradient b/w capillary & mitochondria
  2. contact area b/w RBC & myocyte
  3. distance b/w capillary & mitochondria
56
Q

what does thickness mean fr distance b/w capillary and mitochondria muscle diffusion capacity ?

A

thickness is bad, increased thickness means more difficult to travel across

57
Q

FILL IN THE BLANK

“any condition that alters any of the three muscle diffusion capacity variables will affect ___________ “

A

O2 delivery

58
Q

describe the effect of driving pressure on VO2 max during hypoxia :

A

25% less in hypoxia

59
Q

what is hypoxia ?

A

low levels of oxygen in your body tissues

60
Q

describe the effect of driving pressure on VO2 max during decreased pressure :

A

decreased diffusive deliver (decreased VO2 max)

61
Q

what happens to RBC spacing during exercise ?

A

greater convective blood flow increases number of blood cells in a given capillary (less RBC spacing)

62
Q

what does convective mean ?

A

increased blood flow / more fluid

63
Q

what is hematocrit ?

A

the ratio of the volume of red blood cells to the total volume of blood

64
Q

what does an increase in hematocrit mean for functional surface area for diffusion ?

A

increased functional surface area for diffusion

65
Q

what does an increase in hematocrit mean for diffusive O2 delivery ?

A

increased diffusive O2 delivery

66
Q

what is capillarization ?

A

increase capillaries in contact with muscle fibers

67
Q

what does this mean if capillaries are more in contact with muscle fibers ?

A

has more gas exchange occurring

68
Q

what is an example of increase capillaries in contact with muscle fibers ?

A

aerobic exercise training increases capillary t muscle fiber ratio

69
Q

what is the capillary-to-fiber-ratio for preexercise for a well trained man ?

A

1.5

70
Q

what is the capillary-to-fiber-ratio for post exercise for a well trained man ?

A

1.6

71
Q

what is the capillary-to-fiber-ratio for preexercise for a untrained man ?

A

1.1

72
Q

what is the capillary-to-fiber-ratio for post exercise for a untrained man ?

A

1.1

73
Q

when oxygenated blood reaches muscle capillaries, what happens to the bond between O2 and Hb molecules?

A

the bond between O2 and Hb molecules weakens

74
Q

as RBCs pass single file through the tiny capillaries that surround muscles, what is released from Hb ?

A

O2 is released from Hb

75
Q

when oxygenated blood reaches muscle capillaries, why does the bond between O2 and Hb molecules weaken ?

A

because of the concentration / if O2 weakens then Hb naturally does as well

76
Q

is capillary PO2 > OR < cytosolic PO2 so O2 diffuses int the sarcoplasm

A

>

77
Q

once inside the sarcoplasm, O2 can do what two things ?

A

diffuse directly into mitochondria OR bind to myoglobin

78
Q

what does myoglobin shuttle ?

A

O2 from the cytosol to the mitochondria

79
Q

when does myoglobin shuttle O2 from the cytosol to the mitochondria ?

A

when cytosolic PO2 falls to critical levels during exercise

80
Q

during diffusive O2 delivery during exercise, once in the mitochondria, what is O2 drawn to ?

A

drawn to cytochrome c oxidase (complex 4)

81
Q

during diffusive O2 delivery during exercise, once in the mitochondria,O2 is drawn to cytochrome c oxidase (complex 4)… what happens here ?

A

it accepts electrons delivered by oxidation of CHO or FAT

82
Q

in the last step of diffusive O2 delivery during exercise, what does reduced O2 then pick up ?

A

two H+ from the surrounding medium to form water

Exercise Physiology 2230 (21 decks)

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