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physiology Flashcards

1
Q

what is internal respiration?

A

intracellular mechanism of which consumes oxygen and produces co2

food + oxygen = energy + carbon dioxide (+ water)

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2
Q

what is external respiration?

A

the 4 sequence of events that lead to the exchange of O2 and co2 between the external environment and the cells of the body

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3
Q

what are the steps of external respiration?

A
  1. ventilation- air in and out of lungs
  2. gas exchange between alveoli and blood
    - exchange of o2 in alveoli
  3. gas transport in the blood- binding of o2 and co2 to blood
  4. gas exchange at tissue level
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4
Q

what 4 systems are involved in external respiration?

A
  1. respiratory system
  2. cardiovascular system
  3. haematology
  4. nervous system
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5
Q

what is boyle’s law?

A

at a constant temp- as the volume of the gas increases the pressure of the gas decreases.

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6
Q

what must happen to intra-alveolar pressure in order for air to flow into the lungs during inspiration?

A

intra-alveolar pressure must be lower than atmospheric pressure.

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7
Q

how does air flowing into the lungs occur?

inspiration

A

Rib cage expands and moves upwards

caused by contraction of the diaphragm - increases volume of thorax

and external intercostal muscles- contracts and lifts ribs and sternum

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8
Q

what are the two forces which hold the thoracic wall and the lungs in close opposition?

A
  1. intrapleural fluid cohesiveness- water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart. Keeps pleural membrane together
  2. negative intrapleural pressure- sub atmospheric intrapleural pressure creates a transmullar pressure gradient across the lung wall and also the chest wall.
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9
Q

What are the main pressures involved in pulmonary ventilation?

A
  1. Atmospheric pressure at sea level
  2. intra-alveolar pressure- pressure within the lung alveoli
  3. intrapleural pressure- pressure exerted outside the lungs but within the pleural cavity
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10
Q

What are the usual pressure values of these pressures

A
  1. atmospheric pressure- 760 mm Hg
  2. intra-alveolar- when equal to atmospheric pressure it is 760 mm Hg
  3. Intra pleural- 756 mm Hg
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11
Q

what is the name of the mechanism describing the movement of external intercostal muscles during inspiration?

A

bucket handle mechanism

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12
Q

what nerves supply the diaphragm?

A

phrenic nerve from C3,4,5

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13
Q

what does inspiration do the intra alveolar pressure?

A

makes it decrease due to increase size of lungs= more volume

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14
Q

what is the difference between inspiration and expiration in regards to the process?

A

inspiration is active- requires contraction of muscles

(normal) expiration is passive- relies on relaxation of inspiratory muscles

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15
Q

when the diaphragm relaxes what causes the lungs decrease in size during expiration?

A

its elastic recoil properties from the elastic connective tissue

alveolar surface tension( most important factor)

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16
Q

what happens to the intra alveolar pressure during expiration?

A

increase due to decrease in volume. Pressure rises above atmospheric pressure allowing for expiration

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17
Q

what is transmural/transpulmonary pressure?

A

It is the difference in pressure between the alveolar and pleural pressures.

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18
Q

what is alveolar surface tension?

A

The characteristic of water particles on the surface to have a strong attraction to water particles on the inner surface due to cohesion.

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19
Q

what reduces alveolar surface tension?

A

surfactant

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20
Q

what is a surfactant

A

A mixture of Phospholipids, proteins, and ions. It is a surface-active agent of water.

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21
Q

where is pulmonary surfactant secreted from?

A

Type ii alveolar epithelial cells. These cells are granular.

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22
Q

What is la place’s law?

A 
P= 2T/r
where:
P = inward directed collapsing pressure
T = surface tension
r = radius of the alveoli
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23
Q

what does la place’s law suggest?

A

smaller the alveoli the bigger the risk of it collapsing

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24
Q

why are surfactants so important?

A

prevents smaller alveoli collapsing and emptying contents into larger alveoli

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25
Q

besides from transmural pressure and pulmonary surfactant what other major force tries to keep alveoli open?

A

alveolar interdependence

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26
Q

what is alveolar interdependence?

A

When a collapsing alveolus stretches the ones around it.

This in turn causes the alveoli surrounding it to recoil and pull it open.

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27
Q

what are the accessory muscles of inspiration?

A

sternocleidomastoid - lifts the sternum

pectoral

scalenus

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28
Q

when are accessory muscles used for inspiration

A

during forceful inspiration

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29
Q

what are the muscles of active expiration?

A
  1. Abdominal muscles 2. Internal intercostal muscles
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30
Q

What is the tidal volume? (TV)

ii. what is its average value ( in a young adult male)

A

volume of air entering or leaving lungs during a single breath

ii. 0.5 L

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31
Q

what is the inspiratory reserve volume?

ii. average value?

A

extra volume of air that can be maximally inspired over and above the typical resting tidal volume

ii. 3.0 L

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32
Q

what is the expiratory reserve volume?

ii. average value?

A

extra volume of air that can be maximally actively expired over and above the typical resting tidal volume

ii. 1.0 L

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33
Q

what is the residual volume?

ii. average value?

A

minimum volume of air remaining in the lungs even after a maximal expiration

ii. 1.2 L

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34
Q

What is the definition of inspiratory capacity?

ii. average value?

A

maximum volume of air that can be inspired at the end of a normal expiration.

ii. 3.5 L

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35
Q

how do you calculate the inspiratory capacity?

A

Tidal volume plus the inspiratory reserve volume

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36
Q

what is the Functional residual capacity?

ii. average value?

A

volume of air in lungs at end of normal passive expiration.

ii. 2.2 L

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37
Q

how do you calculate the FRC?

A

expiratory reserve volume plus the residual volume.

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38
Q

what is the vital capacity?

ii. average value?

A

maximum volume of air that can be moved out during a single breath following a maximal inspiration

ii. 4.5 L

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39
Q

How do you calculate the VC?

A

inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume.

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40
Q

What is the total lung capacity?

ii. average value?

A

Total volume of air in the lungs

ii. 5.7 L

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41
Q

How do you calculate TLC?

A

you can’t their effect on the pop scene is unquantifiable

Vital capacity+ residual volume

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42
Q

when does the residual volume increase?

A

when elastic recoil of the lung is decreased

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43
Q

why can’t TLC be measured by a spirometry?

A

because the residual volume cannot be recored by a spirometry. you need the RV to calculate the spirometry

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44
Q

What is the function of a volume time curve?

A

allows you to calculate Forced vital capacity (FVC) and forced expiratory volume in one second ( FEV1)

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45
Q

what is FEV1?

A

volume of air that can be expired during the first second of expiration in an FVC determination

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46
Q

What is the FEV1/FVC ratio?

A

proportion of the FVC that can be expired in the first second

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47
Q

What equipment is used to calculate volume time curve?

A

spirometry

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48
Q

What is the normal % of a FEV1/FVC ratio?

ii. what does it suggest if this value is below this number?

A

> 70%

ii. obstructive lung disease

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49
Q

what is the main role of parasympathetic stimulation on the airways?

A

bronchoconstriction

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50
Q

what is the main role of sympathetic stimulation on the airways?

A

bronchodilation

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51
Q

How do you calculate airway resistance

A

Flow= change in pressure/resistance

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52
Q

why is there only a small pressure gradient in the airway for air movement?

A

as resistance to flow is very low

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53
Q

what happens to intrapleural pressure in:

  1. inspiration
  2. expiration
A
  1. decrease

2. increase- causes dynamic compression

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54
Q

what is the effect of dynamic airway compression?

A

not effective on normal people

only effects patients with obstructive lung disease by making it harder to actively expire

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55
Q

what does dynamic airway compression effect? ( anatomically speaking)

A

compresses alveoli and airway

compressing alveoli- helps push air out

compressing airway- a nuisance!

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56
Q

why does obstructive lung disease not benefit from dynamic compression?

A

the driving pressure between the alveolus and airway is lost over the obstructive segment.

causes fall in airway pressure resulting in airway compression from the pleural pressure

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57
Q

what is a peak flow meter?

A

records peak flow rate-measures the maximum speed at which a patient can move air out of lungs

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58
Q

what is the peak flow rate?

A

assesses the airway function

useful for obstructive lung disease

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59
Q

what is lung compliance?

A

The ability for the lungs to expand/stretch and how much effort is required.

i.e. less compliance= more effort required for the lungs to stretch

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60
Q

what factors decrease lung compliance?

A

Pulmonary fibrosis

Pulmonary oedema

Lung collapse

Pneumonia

lack of surfactant

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61
Q

Decreased pulmonary compliance has what effect on pressure difference in the lungs?

A

Greater pressure difference needed to change volume of lungs

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62
Q

what effect has lung compliance have on a volume time curve?

A

shows patient to have restrictive patterns

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63
Q

why might abnormal increase of lung compliance occur?

ii. what is this common in?

A

loss of elastic recoil of the lungs

ii. emphysema- hyperinflation of lungs

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64
Q

compliance increases with age true or false?

A

true

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65
Q

when does work of breathing increase?

A

decrease in lung compliance

decrease in elastic recoil

increase in airway resistance

when lungs are required to increase ventilation

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66
Q

what is Anatomical dead space?

A

the non exchange areas where air may remain in the respiratory system

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67
Q

what is pulmonary ventilation?

A

volume of air breathed in and our per minute

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68
Q

what is alveolar ventilation?

A

volume of air exchange between the atmosphere and alveoli per minute

represents new air available of gas exchange with blood

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69
Q

How do you calculate pulmonary ventilation?

A

Tidal volume x Respiratory rate= PV (L/min)

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70
Q

What is the normal respiratory rate?

A

12-20 breaths per minute

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71
Q

How do you calculate alveolar ventilation?

A

(Tidal volume-dead space)x respiratory rate

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72
Q

why does alveolar ventilation have a lower value than pulmonary ventilation?

A

As it takes into consideration anatomical dead space

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73
Q

Because of anatomical dead space what should you do to increase pulmonary ventilation?

A

increase the depth of breathing (Increase Tidal volume)

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74
Q

what is the difference between ventilation and perfusion?

A

Ventilation: rate at which gas is passing through the lungs (rate of airflow)

perfusion: rate at which blood is passing through the lungs (rate of blood flow)

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75
Q

what is alveolar dead space?

A

refers to alveoli with poor ventilation or perfusion

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76
Q

Accumulation of CO2 in alveoli due to increase perfusion causes what?

A

decreased airway resistance= increased airflow

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77
Q

Increase in alveolar O2 concentration as a result of increased ventilation causes what?

A

pulmonary vasodilation

increased blood flow

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78
Q

What factors occur when Perfusion is greater than ventilation?

A

CO2 increases in area

O2 decrease in area

dilation of local airways

Constriction of local blood vessels

Airflow increase

Blood flow decrease

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79
Q

What factors occur when ventilation is greater than perfusion?

A

Co2 decreases in area

O2 increase in area

constriction of local airways

dilation of local blood vessels

airflow decrease

blood flow increase

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80
Q

what is the difference between Physiological and anatomical dead space?

ii. is there a difference in value?

A

Physiological dead space includes alveolar dead space. (Anatomical dead space + alveolar dead space)

Anatomical dead space does not

ii.In healthy individuals the values are equal. However, Unhealthy individuals can have physiological dead space being 1 to 2 litres greater.

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81
Q

What happens to pulmonary and systemic arterioles during:

  1. Decreased O2
  2. Increased O2
A
  1. Pulmonary: vasoconstriction
    Systemic: Vasodilation
  2. Pulmonary: Vasodilation
    Systemic: vasoconstriction
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82
Q

What are the four factors which effect the rate of Gas exchange across the alveolar membrane?

A
  1. Partial Pressure gradient of O2 and CO2
  2. Diffusion coefficient of O2 and Co2
  3. Surface area of alveolar membrane
  4. thickness of alveolar membrane
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83
Q

What is Dalton’s law of partial pressure?

A

Total pressure exerted by gaseous mixture= sum of the partial pressures of each individual component in the gas mixture
P total = P1 + P2 + P3…)

84
Q

What is the partial pressure of a gas?

A

The pressure that one gas in a mixture would exert if it occupied the total volume by itself at a given temperature

85
Q

what is the partial pressure of oxygen in atmospheric air?

A

760x0.21= 160 mmHg

86
Q

what contributes to about 47mmHg of the total pressure in the lungs?

A

water vapour pressure

87
Q

How do you calculate the value for the pressure of inspired air?

ii. what is its value at sea level?

A

Atmospheric pressure- water vapour

ii. 713 mmHg (760-47)

88
Q

What is the alveolar gas equation?

A

PAO2 = PiO2- [PaCO2/0.8]

89
Q

what does PAO2 mean?

A

partial pressure of o2 in alveolar air

90
Q

what does PIO2 mean?

A

partial pressure of O2 in inspired air

91
Q

what does PACO2 mean?

A

partial pressure of CO2 in arterial blood

92
Q

What is the respiratory exchange ratio?

ii. what is its value?

A

Ratio of CO2 produced /O2 consumed

ii. 0.8

93
Q

What is the normal value of arterial PCO2?

A

40 mmHg

94
Q

at a normal arterial PCO2 what is the PAO2?

A

PAO2 = 150mmHg - [40/0.8]

=100mHg

95
Q

how do you convert mmHg pressure to kPa?

A

kPa = mmHg/7.5

96
Q

Across pulmonary capillaries what is the partial pressure gradient value of PAO2?

( from alveoli to blood)

A

60 mmHg ( 8kP)

100-40

97
Q

Across pulmonary capillaries what is the partial pressure gradient value of PCO2?

(from blood to alveoli)

A

6 mm Hg (0.8 kP)

46-40

98
Q

Across systemic capillaries what is the partial pressure gradient value of PaO2?

( blood to tissue cell)

A

> 60 mm Hg

100-<40

99
Q

Across systemic capillaries what is the partial pressure gradient of PCo2

(tissue cell to blood)

A

> 6 mmHg

>46-40

100
Q

why is the partial pressure gradient for CO2 much smaller than O2?

A

CO2 is more soluble in membranes than O2 due to it having a much higher diffusion coefficient

101
Q

What is the diffusion coeffecient?

A

Solubility of a gas in membranes

102
Q

what is the difference between PaO2 and PAO2?

A

PaO2- arterial PO2

PAO2- alveolar PO2

103
Q

what does a large gradient between PAO2 and PaO2 suggest?

A

Problems with gas exchange in lungs

or

Right to left shunt in the heart

104
Q

What is Fick’s law of diffusion?

A

Amount of gas that moves across a shoot tissue in unit time is proportional to the area of the sheet but indirectly proportional to the thickness of the sheet

105
Q

what does pulmonary circulation recieve?

A

the entire cardiac output

106
Q

why is a small gradient between PAO2 and PaO2 normal?

A

ventilation-perfusion match is usually not perfect

107
Q

what is the role of Type 1 alveolar cells?

A

gas exchange

108
Q

what encircles each alveolus?

A

pulmonary capillaries

109
Q

Discuss the four main factors’ influence on the rate of gas exchange.

A
  1. As Partial pressure gradient increases so does rate of gas exchange
  2. As Diffusion coefficient increase so does Gas exchange rate
  3. As Surface area increase so does rate of gas exchange.
  4. As thickness of membrane increase the gas exchange rate decreases
110
Q

What are the main non-respiratory functions of the respiratory system?

A

Route for water loss and heat elimination

Enhances venous return

Maintains acid-base balance

Enables speech

Defends inhaled foreign matter

Removes, modifies, activates or inactivates various materials passing through the pulmonary circulation

Nose smells stuff

111
Q

What is Henry’s Law?

A

The amount of a given gas dissolved in a given type and volume of liquid (blood) at a constant temperature is proportional to the partial pressure of the gas in equilibrium with the liquid

therefore: if the partial pressure in the gas phase is increased the concentration of the gas in the liquid phase would increase proportionally.

112
Q

what is the value of cardiac output at resting conditions?

A

5L/min

113
Q

what is the rate of dissolved o2 which reaches tissues in resting conditions?

A

15ml/min

114
Q

What is the value of cardiac output at strenuous exercise?

A

30 L/min

115
Q

What is the rate of dissolved O2 which reaches tissues in strenuous conditions?

A

90ml/min

116
Q

At resting conditions what is rate of total oxygen consumption in body cells?

A

250ml/min

117
Q

what are the two main ways in which oxygen is transported?

A
  1. Bound to haemoglobin (98.5%)

2. dissolved ( 1.5%)

118
Q

What is the volume of dissolved oxygen in one litre of blood?

A

3 ml

119
Q

what is the volume of oxygen in one litre of blood?

A

200 ml

120
Q

How many haem groups are in one Hb molecule?

A

4 haem groups- oxygen revsibly binds to each one

121
Q

What is the primary factor which determines the percent saturation of haemoglobin with O2?

A

Po2

122
Q

How many alpha chains are in one Hb molecule?

A

2

123
Q

How many beta chains are in one Hb molecule?

A

2

124
Q

When is haemoglobin is considered fully saturated?

A

when all Hb present is carrying maximum O2 load

125
Q

what is the average resting PO2 at systemic capillaries?

A

5.3 kPa

126
Q

what is the normal Po2 at pulmonary capillaries?

A

13.3 kPa

127
Q

How do you calculate the oxygen delivery index?

A

Oxygen content of arterial blood x Cardiac index= DO2L( ml.min/meter2)

128
Q

what is Cao2?

A

oxygen content of arterial blood

129
Q

What is the cardiac index?

A

Cardiac output to the body surface area( size of individual)

130
Q

What is the normal range of cardiac index?

A

2.4-4.2L/min/meter^2

131
Q

How do you calculate Cao2?

A

1.34x{Hb}xSaO2

132
Q

what is Sao2?

ii. what is it determined by?

A

Percentage of haemoglobin with oxygen in arterial blood.

ii. Po2

133
Q

How much oxygen does one gram of Hb carry when fully saturated?

A

1.34 ml

134
Q

What does the partial pressure of inspired oxygen depend on?

A

total pressure and proportion of oxygen in gas mixture

135
Q

What factors does the partial pressure of inspired oxygen depends on?

A

Total pressure ( e.g. atmospheric pressure)

proportion of oxygen in gas mixture (21% in atmosphere)

136
Q

What does the binding of the first O2 molecule to Hb do?

A

Increases the affinity of Hb for O2

(sigmoid curve)- flattens when all sites are occupied

137
Q

What does the flat upper portion of the sigmoid curve mean?

A

That a moderate fall in Alveolar Po2 will not affect oxygen loading

138
Q

What does the steep lower part of the sigmoid curve mean?

A

Peripheral tissues get a lot of oxygen for a small drop in capillary Po2

139
Q

What is the Bohr effect?

A

when the dissociation curve shifts to the right

increase in CO2 in the blood causes O2 to be displaced from the hemoglobin

140
Q

What factors causes the bohr effect to occur?

A

Increase in Pco2

increase in [H+]

increase in temperature

Increase in 2,3-biphosphoglycerate

141
Q

Where does Bohr effect occur?

A

at tissues

142
Q

How does fetal haemoglobin differ from adult haemoglobin?

A
  1. HbF has 2 alpha and 2 gamma (rather than 2 beta) subunits
  2. HbF interacts less with 2,3-biphosphoglycerate in erythrocytes
  3. HbF has a higher affinity for O2

This means Fetal dissociation curve will be to the left of adult curve ( binds at a lower PO2)

143
Q

What does the positioning of the fetal dissociation curve in comparison of the adult dissociation curve?

A

Oxygen transfer from mother to foetus can occur even if PO2 is low

144
Q

What is myoglobin?

A

an iron containing protein which resembles Hb and is found in skeletal and cardiac muscles

145
Q

How many haem groups are in one myoglobin molecule?

A

one

146
Q

What is the difference between Myoglobin and haemoglobin?

A

Myoglobin is found in Muscle cells ( Haemoglobin in RBC)

one Haem group in myoglobin ( 4 in haemoglobin)

Dissocaition curve for Mb is hyperbolic (sigmoid for Hb)

Mb releases O2 at much lower Po2

147
Q

What is the role of Myoglobin?

A

Provides a short-term storage of O2 for anaerobic conditions

148
Q

How is CO2 transported in blood starting from most popular to least?

A
  1. Bicarbonate (60%)
  2. Carbamino compounds (30%)
  3. solution (10%)
149
Q

What is the formula for bicarbonate formation?

ii. where does it occur

A

CO2 + H2O (reversible with) H2CO3 (reversible with) H+ + HCO3-

ii. erythrocyte

150
Q

What enzyme catalyses the formation of the bicarbonate?

A

Carbonic anhydrase

151
Q

When bicarbonate diffuses out of Erythrocyte what occurs after?

A

chloride shift in order for no build up of electric change takes place during gas exchange

152
Q

what happens to the hydrogen ions that are formed during the bicarbonate reaction?

A

binds to haemoglobin to form haemoglobinic acid

153
Q

How are carbamino compounds formed?

A

Combination of Co2 with terminal amine groups in blood proteins

154
Q

What does carbamino compounds bind to?

A

haemoglobin- to form carbamino-haemoglobin

155
Q

Reduced Hb can bind more Co2 than HBO2 true or false?

A

true

156
Q

What is the haldane effect?

A

Removing of O2 from Hb increases the ability of Hb to pick up Co2 and Co2 generated H+

157
Q

What do the Bohr effect and haldane effect allow to occur?

A

O2 liberation ( bohr shift)

and uptake of CO2 and CO2 generated H+ (Haldane effect)

to occur in tissues

158
Q

what neurones generate the breathing rhythm (act as a pacemaker) for respiration?

A

pre-botzinger complex in the medullary respiratory centre

159
Q

What does the respiratory control centres in the brain stem consist of?

A

Pons respiratory centre

Medullary respiratory centre

160
Q

What does the Pons respiratory centre consist of?

A

Pneumotaxic centre

Apneustic centre

161
Q

What does the Medullary respiratory centre consist of?

A

Dorsal respiratory group

Ventral respiratory group

162
Q

what causes contraction of inspiratory muscles and therefore causes inspiration?

A

Rhythm generated by pre Botzinger complex excites the dorsal respiratory group

163
Q

What causes active expiration?

A

Increased firing of dorsal neurones excites the ventral respiratory group neurones which activate expiratory muscles.

does not occur in quiet breathing!

164
Q

What is the role of the Pneumotaxic centre?

A

Terminates inspiration when stimulated

165
Q

What stimulates the Pneumotaxic centre?

A

firing of Dorsal respiratory neurones

166
Q

What is Apneusis?

A

state in which prolonged inhalation occurs with brief expiration. occurs when Pneumotaxic centre is absent

167
Q

What is the function of the apenustic centre?

A

prolong inspiration

168
Q

what are the 4 types of involuntary (reflex) modifications of breathing?

A
  1. Hering-Breuer Reflex
  2. joint receptors reflex
  3. stimulation of respiratory centre
  4. cough reflex
169
Q

What is the Hering-breuer reflex?

A

when the lungs become overly inflated, the pulmonary stretch receptors activate an appropriate feedback response that “switches off” the inspiratory ramp and thus stops further inspiration

170
Q

What are the main factors which increase ventilation during Exercise?

A

Body movement (joint receptors)

Adrenaline release

Cerebral cortex impulse

Increase in body temperature

accumulation of Co2 and H+ from muscle respiring

171
Q

What happens when ventilation is 0 but perfusion is normal?

A

V/Q ratio =0

172
Q

what happens when perfusion is zero but ventilation is normal?

A

V/Q ratio= infinity

173
Q

What is the function of the cough reflex?

A

help clear airways

174
Q

What is the cough reflex activated by?

A

irritation of airways

175
Q

where is the centre of cough reflex?

A

medulla

176
Q

what is the events that occur during a cough reflex?

A
  1. irritation of airways/tight airways
  2. afferent discharge
  3. short intake of breath
  4. closure of larynx
  5. contraction of abdominal muscles to increase intra-alveolar pressure
  6. opening of the larynx
  7. expulsion of air at high speed
177
Q

What type of control system is the chemical control of respiration?

A

negative feedback

178
Q

What are the control variable of the respiartion?

A

blood gas tensions- especially co2

179
Q

what is the function of peripheral chemoreceptors?

A

sense tension of oxygen, co2 and [H+] in the blood

180
Q

Where are peripheral chemoreceptors found?

A

Carotid bodies

Aortic bodies

181
Q

Where are central chemoreceptors found?

A

near the surface of the medulla of the brainstem

182
Q

What is the function of central chemoreceptors?

A

Respond to [H+] of the CSF

183
Q

What separates CSF from blood?

A

Blood brain barrier

184
Q

what is the blood-brain barrier impermeable to?

A

H+ and HCo3-

185
Q

what is the Blood brain barrier permeable to?

A

Co2

186
Q

What is the difference between CSF and blood?

A

Contains less protein and is less buffered than blood

187
Q

what happens when CO2 diffuses across the blood brain barrier?

A

dissociated into H+ ions
as there is a low protein content of the CSF the ions produced arent buffered well and so stimulate the central chemoreceptor

188
Q

what is hypercapnia?

A

presence in the blood of an abnormally high concentration of co2

189
Q

what is hypoxia?

A

deficiency of oxygen in the tissues

190
Q

as hypercapnia increases slightly what happens to ventilation?

A

increases rapidly:

to remove excess CO2

191
Q

what happens to the respiratory centre neurones when there is severe hypoxia?

A

become depressed and so there is a poor ventilation

192
Q

as a general trend, what happens when PO2 increases?

A

ventilation decreases

193
Q

as altitude increases what happens to the partial pressure of oxygen?

A

decreases

194
Q

what are the chemoreceptors which control the hypoxic drive of respiration?

A

peripheral chemoreceptors

195
Q

What causes hypoxia at high altitudes?

A

Decreased PiO2

196
Q

What are the acute responses to hypoxia?

A

Hyperventilation

increased cardiac output

197
Q

What chronic adaptations occur to high altitude hypoxia?

A

Increased RBC production (polycythaemia)- o2 carrying capacity of blood increased

increased production 2,3-BPG within RBC- O2 offloaded more easily into tissues

increased number of capillaries- blood diffuses more easily

increased number of mitochondria- o2 can be used more efficiently

kidneys conserve acid- arterial pH decrease

198
Q

what causes the H+ drive of respiration?

A

peripheral chemoreceptors

199
Q

what is the role of H+ drive of respiration?

A

adjusts for acidosis caused by the addition of non-carbonic acid H+
(eg lactic acid or diabetic ketoacidosis)

200
Q

what does the H+ drive of respiration cause?

A

hyperventilation and increases elimination of CO2 from the body (reduces body acid content)

201
Q

What are the effects of arterial Pco2 on:

  1. peripheral chemoreceptors
  2. central chemoreceptors
A
  1. Weak stimulation

2. strong stimulation- dominant control of ventilation

202
Q

What are the effects of arterial PO2 on:

  1. Peripheral chemoreceptors
  2. Central chemoreceptors
A
  1. Only become important if PO2 fall below 8kPa

2. Severe hypoxia depresses respiratory centre

203
Q

What are the effects of arterial H+ on:

  1. Peripheral chemoreceptors
  2. central chemoreceptors
A
  1. stimulation - important for acid -base balance

2. H+ cannot cross BBB

204
Q

What is the function of the pleural fluid?

A

Lubrication

Provides surface tension

205
Q

what is normal expiration?

A

Is a passive process, controlled by the gaps in firing of dorsal neurons within the medulla

206
Q

what is forced expiration?

A

Is an active process, controlled by the firing of ventral neurons in the medulla

207
Q

what is normal inspiration?

A

Is an active process, controlled by the firing of dorsal neurons within the medulla

My Respiratory (5 decks)

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