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Human physiology > Chapter 18: Gas Exchange and Transport > Flashcards

Chapter 18: Gas Exchange and Transport Flashcards

1
Q

remain relatively constant

A

Arterial blood O2 and CO2 levels

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2
Q

how much oxygen does the body consume at rest?

A

250 mL of O2 each minute

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3
Q

how much CO2 does the body produce at rest?

A

200 mL of CO2 each minute

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4
Q

how much air does the average adult inhale and how much reaches the alveoli?

A
  • 6000mL/min

- 4200mL reaches alveoli

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5
Q

what are the steps of the pulmonary gas exchange?

A 
1. Oxygen enters the
blood at alveolar-
capillary interface
2. Oxygen is trans-
ported in blood
dissolved in plasma
or bound to 
hemoglobin inside
RBCs.
3. Oxygen diffuses into cells
4.CO2 diffuses out of cells
5. CO2 is trans-
ported dissolved,
bound to 
hemoglobin, or
as HCO3-
6. CO2 enters alveoli
at alveolar-capillary
interface.
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6
Q

states that the pressure exerted by a mixture of gasses is equal to the sum of the pressures exerted by the individual gases occupying the same volume.

A

Dalton’s Law-partial pressure of gases

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7
Q

are mixtures of different molecules

A

many gases

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8
Q

= proportion of pressure of entire gas that is due to presence of the individual gas

A

partial pressure of a gas

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9
Q

Ptotal=

A

P1 + P2 + P3 + … Pn

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10
Q

depends on fractional concentration of the gas

A

partial pressure of a gas

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11
Q

what is the equation for the total pressure of a gas mixture?

A

Pgas = %gas × Ptotal

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12
Q

what is the composition of air?

A

-79% nitrogen
21% oxygen
-Trace amounts of carbon -dioxide, helium, argon, and other gases
-Water can be a factor depending on humidity

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13
Q

Pair=

A

760 mm Hg = PN2 + PO2

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14
Q

PN2=

A

0.79 × 760 mm Hg = 600 mm Hg

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15
Q

PO2=

A

0.21 × 760 mm Hg = 160 mm Hg

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16
Q

how much of the air is CO2?

A

0.03%

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17
Q

PCO2=

A

0.0003 × 760 mm Hg = 0.23 mm Hg

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18
Q

what is the composition of air at 100% humidity?

A

Pair = 760 mm Hg = PN2 + PO2 + PH2O

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19
Q

what is PN2 at 100% humidity?

A

PN2 = 0.741 × 760 mm Hg = 563 mm Hg

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20
Q

what is PO2 at 100% humidity?

A

PO2 = 0.196 × 760 mm Hg = 149 mm Hg

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21
Q

what is PH2O at 100% humidity?

A

PH2O = 0.062 × 760 mm Hg = 47 mm Hg

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22
Q

what is PCO2 at 100% humidity?

A

PCO2 = 0.00027 × 760 mm Hg = 0.21 mm Hg

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23
Q

can exist in gas form or dissolved in a liquid

A

gas molecules

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24
Q

affects the amount of gas that goes into solution

A

partial pressure of a gas

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25
Q

what happens if a gas exists over a liquid?

A

the gas will dissolve in the liquid until equilibrium is reached

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26
Q

are the concentration of gas (moles/L) in the air and in the liquid at equilibrium?

A

no

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27
Q

20 times more soluble in blood than O2

A

CO2

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28
Q

what is involved in the exchange of oxygen and carbon dioxide?

A
  • gas exchange in lungs

- gas exchange in respiring tissue

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29
Q

differ from atmospheric pressures

A

alveolar gas pressures

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30
Q

mixes with air rich in CO2 and relatively poor in O2 in dead space of conducting zone

A

fresh air

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31
Q

saturated with water vapor

A

air in alveoli

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32
Q

form a diffusion barrier between lung and blood

A

cells

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33
Q
  • diffuse down pressure gradients

- high pressure–> low pressure

A

gases

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34
Q
  • diffuse down partial pressure gradients

- High partial pressure → low partial pressure

A

gases in gas mixtures

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35
Q
  • diffuses down its own partial pressure gradient

- Presence of other gases is irrelevant

A

a particular gas

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36
Q

how does gas exchange occur in respiring tissue?

A

Gases diffuse down partial pressure gradients

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37
Q

diffuses from blood to cells

A

oxygen (respiring tissue)

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38
Q
  • Oxygen diffuses from blood to cells

- PO2 systemic veins = 40 mm Hg

A

PO2 cells ≤ 40 mm Hg

PO2 systemic arteries = 100 mm Hg

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39
Q
  • Carbon dioxide diffuses from cells to blood

- PCO2 systemic veins = 46 mm Hg

A

PCO2 cells ≥ 46 mm Hg

PCO2 systemic arteries = 40 mm Hg

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40
Q

depends on metabolic activity of the tissue

mixed venous blood

A

Amount of O2 and CO2 that is exchanged in a vascular bed

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41
Q

what does greater rate of metabolism lead to?

A

greater exhcange

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42
Q

vary in different systemic veins

A

PO2 and PCO2

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43
Q

returns to the right atrium and is pumped out of the right ventricle and into the pulmonary artery

A

All systemic venous blood

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44
Q
  • blood in pulmonary artery=?
    • PO2=40mmHg
    • PCO2=46 mmHg
A

mixed venous blood

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45
Q

determine systemic arterial PO2 and PCO2

A

Alveolar PO2 and PCO2

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46
Q

What are the factors affecting alveolar partial pressures?

A
  • PO2 and PCO2 of inspired air (altitude)

- Minute alveolar ventilation (the volume of fresh air reaching the alveoli each minute)

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47
Q

the volume of fresh air reaching the alveoli each minute

A

Minute alveolar ventilation

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48
Q
  • increased ventilation due to increased demand

- Minimal changes in arterial PO2 and PCO2

A

hyperpnea

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49
Q
  • ventilation does not meet demands
  • Arterial PO2 decreases
  • Arterial PCO2 increases
A

Hypoventilation

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50
Q

a state of too little oxygen

A

hypoxia

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51
Q

elevated concentrations of CO2

A

hypercapnia

52
Q

-Inadequate alveolar ventilation
-Decreased lung compliance
Increased airway resistance
CNS depression

A

hypoventilation

53
Q

what can depress the CNS?

A
  • Alcohol poisoning

- Drug overdose

54
Q

what are the factors influencing gas exchange?

A
  • Surface area
  • Diffusion distance
  • Diffusion barrier permeability
55
Q

=surface area x barrier permeability/ distance^2

A

diffusion

56
Q
  • destruction of alveoli means less surface area for gas exchange
  • PO2 normal or low in alveoli
  • arterial PO2 low
A

emphysema

57
Q
  • thickened alveolar membrane slows gas exchagne
  • loss of lung compliance may decrease alveolar ventilation
  • PO2 normal or low in alveoli
  • arterial PO2 low
A

fibrotic lung disease

58
Q
  • fluid in interstitial space increases diffusion distance
  • arterial PCO2 may be normal due to higher CO2 solubility in water
  • exchange surface normal
  • arterial PO2 low
A

pulmonary edema

59
Q
  • increased airway resistance decreases alveolar ventilation
  • bronchioles constricted
  • alveolar PO2 low
  • alveoalr PO2 low
A

asthma

60
Q

what is involved in adequate perfusion of alveoli?

A
  • Local control of ventilation and perfusion
  • Matching of ventilation to perfusion
  • Local control diverts blood away from the under-ventilated region to better-ventilated regions of the lung
61
Q

rate of air flow

A

Ventilation (V)

62
Q

rate of blood flow

A

Perfusion (Q)

63
Q

what happens if ventilation to certain alveoli decreases?

A
  • Increased PCO2 and decreased PO2 in blood and air
  • Increased PCO2 in bronchioles → bronchodilation
  • Decreased PO2 in P. arterioles → vasoconstriction
64
Q

what happens if perfusion to certain alveoli decreases?

A

-Increased PO2 and decreased PCO2 in blood and air
Increased PO2 in P. arterioles → vasodilation
Decreased PCO2 in bronchioles → bronchoconstriction

65
Q

what is ventilation-perfusion mismatch caused by?

A

under-ventilated alveoli

66
Q

what gases are transported in the blood?

A

oxygen and carbon dioxide

67
Q
  • composed of 4 protein globin chains, each centered around a heme group
  • contains 2 alpha chains and two beta chains
A

hemoglobin molecule

68
Q

consists of a porphyrin ring with an iron atom in the center

A

heme group

69
Q

how many erythrocytes per cubic millimeter of blood?

A

5 million erythrocytes

70
Q

how many hemoglobin molecules per erythrocytes?

A

250 million hemoglobin molecules

71
Q

how much oxygen does every liter of arterial blood contain?

A

200 mL of oxygen

72
Q

how much oxygen do cells require at rest?

A

250 mL/ minute at rest

73
Q

what is oxygen transport done by?

A

hemoglobin

74
Q

is O2 soluble in plasma?/

A

not really

75
Q

how much arterial O2 is dissolved in plasma?

A
  • Only 3.0 mL of every 200 mL of arterial blood O2

- 1.5% of plasma

76
Q

what happens to other 197mL of arterial O2 that is not dissolved in plasma?

A

it is transported by hemoglobin

77
Q

when is the blood able to the supply almost 1000mL of oxygen to respiring tissues each minute?

A

when the CO is 5L/min

78
Q
  • Hb + O2 –> Hb*O2 (oxyhemoglobin)

- Hb = deoxyhemoglobin

A

oygen binding to hemoglobin

79
Q

when does alveolar PO2= arterial PO2?

A

when oxygen is transported in the blood without hemoglobin

80
Q

when is oxygen transport at normal PO2 in the blood?

A

with hemoglobin

81
Q

what does the amount of oxygen bound to hemoglobin depend on?

A
  • plasma O2
  • amount of hemoglobin
  • %saturation of Hb x total # of Hb binding sites
82
Q

what does plasma O2 determine?

A

% saturation of hemoglobin

83
Q

what does the amount of hemoglobin determine?

A

total number of hemoglobin binding sites

84
Q

what is the total # of Hb binding sites calculated from?

A

Hb content per RBC x # of RBCs

85
Q

how many oxygen molecules can hemoglobin bind?

A

4

86
Q

what law does the binding of oxygen to hemoglobin follow?

A

**the law of mass action
-More oxygen → more binds to hemoglobin
-Binding of O2 to one subunit increases the affinity of
remaining subunits

87
Q

a measure of how much oxygen is bound to hemoglobin

A

saturation of hemoglobin

88
Q

what does 100% saturation of hemoglobin mean?

A

all four binding sites on hemoglobin have oxygen bound to them

89
Q

what does a shift right on a Hb*O2 dissociation curve mean?

A
  • Decrease in affinity, oxygen is unloaded more easily from hemoglobin (more available to the tissue)
    • Less loading and more unloading
90
Q

what does a shift left on a Hb*O2 dissociation curve mean?

A
  • Increase in affinity, oxygen is loaded more easily onto hemoglobin
    • More loading and less unloading
91
Q

how does a higher temperature affect a Hb*O2 dissociation curve?

A
  • Active tissues
  • Shift right
  • More O2 unloading in tissues
  • More O2 delivery to tissues
  • decreased affinity
92
Q

what is the Bohr effect?

A
  • lower pH increases O2 unloading
  • decreased affinity
  • **Active tissues
    • Produce more acid; pH decreases in tissues
    • Decreased pH causes shift right in saturation curve
    • More O2 is unloaded to tissues
93
Q
  • CO2 reacts with hemoglobin to form carbaminohemoglobin
    • Hb + CO2 –> HbCO2
  • HbCO2 has lower affinity for oxygen than Hb
  • Increased metabolic activity → increases CO2
  • Increased oxygen unloading in active tissue
  • higher PCO2=decreased affintiy
  • lower PCO2=increased affinity
A

carbamino effect (effects of CO2)

94
Q
  • Produced in red blood cells under conditions of low O2 such as high altitude
  • Synthesis inhibited by oxyhemoglobin
  • decreases affinity of hemoglobin for O2, enhancing O2 unloading
A

2,3-DPG (2,3-diphosphoglycerate)

95
Q

how does carbon monoxide affect oxygen transport?

A
  • Hemoglobin has greater affinity for carbon monoxide (CO) than for O2
    • Prevents O2 from binding to hemoglobin
96
Q
  • more soluble in plasma than O2, but still not very soluble

- 7% transported dissolved in plasma

A

carbon dioxide

97
Q

what does CO2 form when it binds to hemoglobin?

A
  • carbaminohemoglobin

- 23% transported bound to hemoglobin

98
Q

what is CO2 converted to by erythrocytes?/

A

*converted to bicarbonate, then transported to plasma
-70% of transported CO2 dissolved in the plasma as
bicarbonate
-Hemoglobin also binds H+

99
Q
  • Enzyme that converts carbon dioxide and water to carbonic acid
  • Law of mass action: an increase in CO2 causes an increase in bicarbonate and hydrogen ions
A

carbonic anhydrase

100
Q

what are the steps of carbon dioxide transport?

A
  1. CO2 diffuses out of cells into systemic
    capillaries.
  2. Only 7% of the CO2 remains dissolved in plasma
  3. Nearly a fourth of the CO2 binds to
    hemoglobin, forming carbaminohemoglobin
  4. 70% of the CO2 load is converted to
    bicarbonate and H+. Hemoglobin buffers H+.
  5. HCO3- enters the plasma in exchange for
    Cl- (the chloride shift).
  6. At the lungs, dissolved CO2 diffuses out of
    the plasma.
  7. By the law of mass action, CO2 unbinds from
    hemoglobin and diffuses out of the RBC
  8. The carbonic acid reaction reverses, pulling
    HCO3- back into the RBC and converting it
    back to CO2.
101
Q

what is the neural control of breathing facilitated by?

A

motor neurons

102
Q

where does the generation of breathing rhythm occur?

A

the brainstem

103
Q

where does peripheral input go to?

A

respiratory centers s

104
Q

respiratory muscles=

A

skeletal muscles

105
Q

what are respiratory muscles controlled by?

A

motor neurons

106
Q

what is involved in inspiration?

A
  • Phrenic nerve → diaphragm

- External intercostal nerve → external intercostal muscles

107
Q

what is involved in expiration?

A

Internal intercostal nerve → internal intercostal muscles

108
Q

what components are involved in generating the breathing rhythm?

A
  • Respiratory control centers of medulla
  • Respiratory control centers of pons
  • Central pattern generator
109
Q

what are the two respiratory control centers located on each side of the medulla?

A
  • Ventral respiratory group (VRG)

- Dorsal respiratory group (DRG)

110
Q

2 expiratory, 1 inspiratory region

A

Ventral respiratory group (VRG)

111
Q

Primarily inspiratory neurons

A

Dorsal respiratory group (DRG)

112
Q

hypothesized to control motor neurons to inspiratory muscles, neurons show ramp like activity in frequency of action potentials

A

inspiratory neurons

113
Q

hypothesized to control motor neurons to expiratory muscles and/or inhibit inspiratory neurons

A

Expiratory neurons

114
Q

what do medullary chemo-receptors monitor?

A

CO2

115
Q

PRG

A

pontine respiratory group

116
Q

VRG

A
  • ventral respiratory group

- in medulla

117
Q

DRG

A
  • dorsal respiratory group

- in medulla

118
Q

NTS

A

nucleus tractus solitarius

119
Q
  • Contains inspiratory, expiratory, and mixed neurons

- May regulate transitions between inspiration and expiration

A

pontine respiratory group

120
Q
  • establishes respiratory cycle
  • -located in thee per-Bötzinger complex
  • mechanism unknown
A

central pattern generator

121
Q

what is the sensory input for quiet breathing?

A
  • Central chemoreceptors
  • Peripheral chemoreceptors
  • Pulmonary stretch receptors
  • Proprioceptors
122
Q

what is the peripheral input to respiratory centers?

A

-Chemoreceptors
-Pulmonary stretch receptors
I-rritant receptors
-Muscle and joint proprioceptors

123
Q

-Detect blood levels of O2 and CO2
-two types
-Peripheral chemoreceptors in
carotid bodies
-Central chemoreceptors in
medulla oblongata

A

chemoreceptors

124
Q
  • Located in carotid bodies near carotid sinus
  • Direct contact with arterial blood
  • Communicate with afferent neurons via chemical messenger
  • Afferent neurons project to medullary respiratory control areas
  • Respond mainly to changes in blood pH
A

peripheral chemoreceptors

125
Q

-Located on the ventral surface of medulla
-Respond to changes in pH of the CSF
-Not directly responsive to CO2
-Respond indirectly to CO2
via pH
-Increased CO2 decreases
pH
-Not responsive to changes in [O2]

A

central chemoreceptors

126
Q

monitor CO2 in cerebrospinal fluid

A

central chemoreceptors

127
Q

monitor CO2, O2, and H+

A

carotid chemoreceptors

Human physiology (17 decks)

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