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1ST YR RESP > Respiratory Physiology > Flashcards

Respiratory Physiology Flashcards

1
Q

<p>What does internal respiration refer to?</p>

A

<p>The intracellular mechanisms which consumes O2 and produces CO2</p>

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2
Q

<p>External Respiration</p>

A

<p>Sequence of events that lead to the exchange of O2 and CO2 between the external environment and cells of the body</p>

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3
Q

<p>How many steps does external respiration involve?</p>

A

<p>Four steps</p>

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4
Q

Explained Steps of External Respiration

A

<p>1. Ventilation - gas exchange between the atmosphere and air sacs in the lungs

2. Exchange - of O2 and CO2 between air in alveoli and blood coming to lungs (in pulmonary arteries)
3. Transport - of O2 and CO2 in the blood between the lungs and the tissues
4. Exchange - of O2 and CO2 between the blood in the systematic capillaries and the body cells</p>

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5
Q

Summarised Four Steps of External Respiration

A
  • Ventilation
  • Gas exchange between alveoli and blood
  • Gas transport in the blood
  • Gas exchange at the tissue level
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6
Q

What are the four body systems involved in external respiration?

A
  • Respiratory system
  • Cardiovascular system
  • Haematology system
  • Nervous system
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7
Q

Definition of Ventilation

A

The mechanical process of moving air between the atmosphere and alveolar sacs

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8
Q

Boyle’s Law

A
  • At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas

To put it simply…
- As the volume of gas increases, the pressure exerted by the gas decreases

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9
Q

For air to flow into the lungs during inspiration the intra-alveolar pressure must become _____ than the atmospheric pressure

A

less

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10
Q

What are the two distinct phases in respiration?

A
  • Inspiration (inhalation)

- Expiration (exhalation)

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11
Q

During inspiration the _____ and _____ expand as a result of what?

A
  • Thorax
  • Lungs
  • Contraction of inspiratory muscles
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12
Q

Where is the thorax?

A

Region of the body formed by the…

  • Sternum
  • Thoracic Vertebrae
  • Ribs
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13
Q

What are the two forces that hold the thoracic wall and lungs in close opposition?

A

(1) The intrapleural fluid cohesiveness

(2) The negative intrapleural pressure

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14
Q

What is meant by the INTRAPLEURAL FLUID COHESIVENESS

A
  • Water molecules in the inrapleural fluid are attracted to each other and resist being pulled apart
  • So membranes stick together
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15
Q

What is meant by the NEGATIVE INTRAPLEURAL PRESSURE

A
  • The sub-atmospheric intrapleural pressure create a transmural pressure gradient across the lung wall and chest wall
  • Lungs are forced to expand outwards while the chest is forced to squeeze inwards
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16
Q

Three pressures important in ventilation

A
  • Atmospheric pressure
  • Intra-alveolar (intrapulmonary) pressure
  • Intrapleural (intrathoracic) pressure
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17
Q

Inspiration is an ____ process depending on _____ _______

A
  • Active

- Muscle contraction

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18
Q

Volume of the thorax is increased _______ by contraction of the ________ flattening out its dome shape

A
  • vertically

- diaphragm (major inspiratory muscle)

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19
Q

What muscle contraction lifts the ribs and moves out the sternum?

A

The external intercostal muscle contraction

“bucket handle” mechanism

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20
Q

During inspiration the chest wall and lungs are…

A

stretched

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21
Q

Increase in size of lungs during inspiration does what to the intra-alveolar pressure?

A

Causes the intra-alveolar pressure to fall

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22
Q

Why does the intra-alveolar pressure fall when the size of lungs increases?

A

The air molecules become contained in a larger volume (BOYLE’S LAW)

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23
Q

What occurs after the increase in size of lungs during inspiration?

A
  • Air then enters the lungs down its pressure gradient until the intra-alveolar pressure becomes equal to atmospheric pressure
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24
Q

Normal expiration is a ______ process brought about by the ______ of inspiratory muscles

A
  • Passive process

- Relaxation

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25
Q

Process of Expiration

A
  • Chest wall and stretched lungs recoil to preinspiratory size because of their elastic properties
  • Recoil of lungs makes the intra-alveolar pressure rise as air molecules are contained in a smaller volume (BOYLE’S LAW)
  • Air then leaves lungs down pressure gradient until intra-alveolar pressure becomes equal to atmospheric pressure
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26
Q

What is Pneumothorax

A

Air in the pleural space (normally filled with fluid not air)

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27
Q

-

A
  • Spontaneous
  • Traumatic
  • Iatrogenic
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28
Q

How does pneumothorax occur?

A
  • Air enters the pleural space from outside or from the lungs
  • This air can abolish the transmural pressure gradient leading to the lung collapsing
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29
Q

What can happen with pneumothorax?

A

The lung can collapse

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30
Q

Small pneumothorax can be what?

A

Symptomatic

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31
Q

What are the symptoms of pneumothorax?

A
  • Shortness of breath

- Chest pain

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32
Q

What are the physical signs of pneumothorax?

A
  • Hyperresonant
  • Percussion Note
  • Decreased/absent breath sounds
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33
Q

What causes the lungs to recoil during expiration?

A
  • Elastic connective tissue in the lungs (whole structure bounces back into shape)
  • Alveolar surface tension
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34
Q

What is alveolar surface tension?

A
  • Attraction between water molecules at liquid air interface
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35
Q

What does alveolar surface tension produce?

A

Produces a force which resists the stretching of the lungs

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36
Q

What would happen if the alveoli were lined with water alone

A

The surface tension would be too strong so the alveoli would collapse

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37
Q

What does the law of LaPlace state?

A

The smaller alveoli (with smaller radius - r) have a higher tendency to collapse

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38
Q

What is pulmonary surfactant?

A

A complex mixture of lipids and proteins secreted by type II alveoli

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39
Q

What does pulmonary surfactant do?

A

Pulmonary surfactant lowers the surface tension of smaller alveoli more than that of large alveoli

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40
Q

What is the purpose of pulmonary surfactant lowering the surface tension of smaller alveoli

A

Prevents the smaller alveoli from collapsing and emptying their air contents into larger alveoli

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41
Q

LaPlace’s Law Formula

A

P = 2T / r

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42
Q

What is P in LaPlace’s Law?

A

The inward directed collapsing pressure

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43
Q

What is T in LaPlace’s Law?

A

Surface Tension

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44
Q

What is r in LaPlace’s Law?

A

Radius of the bubble

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45
Q

Developing fetal lungs are unable to do what?

A

Unable to synthesize surfactant until late in preganancy

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46
Q

Premature babies may not have enough of what?

A

Pulmonary surfactant

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47
Q

Premature babies not having enough pulmonary surfactant causes what?

A

Respiratory distress syndrome of the new born

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48
Q

Respiratory distress syndrome means the baby has to do what to breathe?

A

Make very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs

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49
Q

What is another factor that keeps the alveoli open?

A

The Alveolar Interdependence

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50
Q

What is the alveolar interdependence

A
  • If and alveolus starts to collapse, surrounding alveoli are stretched
  • Surrounding alveoli then recoil exerting expanding forces in the collapsing alveolus to open it
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51
Q

Name the forces keeping the alveoli open

A
  • Transmural pressure gradient
  • Pulmonary surfactant
  • Alveolar Interdependence
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52
Q

Name the forces promoting alveolar collapse

A
  • Elasticity of stretched lung connective tissue

- Alveolar surface tension

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53
Q

What are the major inspiratory muscles?

A
  • Diaphragm

- External Intercostal Muscles

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54
Q

What are the Accessory Muscles of Inspiration?

contracts only during forceful inspiration

A
  • Sternocleidomastoid
  • Scalenus
  • Pectoral
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55
Q

What are the muscles of active expiration?

contracts only during active expiration

A
  • Abdominal Muscles

- Internal Intercostal Muscles

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56
Q

What is IC?

A

Inspiratory capacity

- Maximum volume of air that can be inspired at the end of a normal quiet expiration

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57
Q

What is ERV?

A

Expiratory Reserve Volume
- Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume

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58
Q

What is RV?

A

Residual Volume

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

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59
Q

What is VC?

A

Vital Capacity

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

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60
Q

What is IRV?

A

Inspiratory Reserve Volume

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

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61
Q

What is TV?

A

Tidal Volume

- Volume of air entering or leaving lungs during a single breath

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62
Q

What is FRC?

A

Functional Residual Capacity

- Volume of air in lungs at the end of normal passive expiration

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63
Q

What is TLC?

A

Total Lung Capacity

- Total volume of air the lungs can hold

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64
Q

What is the average value of tidal volume?

A

0.5L

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65
Q

What is the average value of inspiratory reserve volume?

A

3.0L

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66
Q

Average value of expiratory reserve volume?

A

1.0L

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67
Q

Average value of residual volume?

A

1.2L

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68
Q

What is the inspiratory capacity average value?

A

3.5L

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69
Q

What is the inspiratory capacity equation?

A

IC = IRV + TV

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70
Q

What is the functional residual capacity equation?

A

FRC = ERV + RV

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71
Q

What is the functional residual capacity average value?

A

2.2L

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72
Q

What is the vital capacity equation?

A

VC = IRV + TV + ERV

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73
Q

What is the vital capacity average value?

A

4.5L

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74
Q

What is the total lung capacity equation?

A

TLC = VC + RV

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75
Q

What is the total lung capacity average value?

A

5.7L

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76
Q

Residual volume cannot be measured by what?

A

Cannot be measured by spirometry

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77
Q

If residual volume cannot be measured by spirometry what else cannot be measured?

A

Total lung volume

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78
Q

Residual volume increases when…

A

Elastic recoil of the lungs is lost e.g. in emphysema

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79
Q

What does a volume time curve allow you to determine?

A
  • Forced Vital Capacity (FVC)

- Forced Expiratory Volume in one second (FEV1)

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80
Q

What is forced vital capacity (FVC)?

A

The maximum volume that can be forcibly expelled from the lungs following a maximum inspiration

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81
Q

What is forced expiratory volume in one second (FEV1)?

A

The volume of air that can be expired during the first second of expiration in a forced vital capacity (FVC) determination

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82
Q

What is the FEV1/FVC ratio?

A

The proportion of forced vital capacity that can be expired in the first second

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83
Q

How to calculate the FEV1/FVC ratio?

A
  • (FEV1/FVC) X 100%

- Normally more than 70%

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84
Q

Dynamic Lung Volumes are useful in the diagnosis of what?

A

Obstructive and Restrictive lung disease

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85
Q

What is the formula to calculate airway resistance?

A

F = deltaP / R

  • F = flow
  • P = pressure
  • R = resistance
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86
Q

Resistance to flow in the airway is normally very ______ and therefore air moves with a small _____ _____

A
  • low

- pressure gradient

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87
Q

What is primary determinant of airway resistance?

A
  • The radius of the conducting airway
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88
Q

What does parasympathetic stimulation do to the bronchi?

A

Causes bronchoconstriction

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89
Q

What does sympathetic stimulation do to the bronchi?

A

Causes bronchodilation

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90
Q

REMEMBER

Sympathetic stimulation does what?

A

Fight or flight

Reacts to stresses

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91
Q

REMEMBER

Parasympathetic stimulation does what?

A

Rest and digest

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92
Q

What is a disease state?

A
  • A disordered or incorrectly functioning organ
  • E.g. COPD or asthma
  • Can cause significant resistance to airflow
  • Makes expiration more difficult than inspiration so more and more air gets trapped in the lungs
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93
Q

What happens to the airways during inspiration?

A
  • Pulled open by the expanding thorax

- Intrapleural pressure falls

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94
Q

Where is the pleural cavity?

A

Between the parietal pleura (outter layer) attached to the chest wall and the visceral pleura (inner layer attached to lungs)

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95
Q

What happens to the chest during expiration?

A
  • The chest recoils

- Intrapleural pressure rises

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96
Q

What is the intrapleural pressure?

A
  • The pressure within the pleural cavity

- Pressure within the pleural cavity is slightly less than atmospheric pressure normally

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97
Q

What does pressure being applied to the alveolus do?

A

Helps push air out of the lungs

- Pressure applied not always desirable as can compress the alveolus

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98
Q

Rising pleural pressure during active expiration does what?

A

Compresses the alveoli and the airway

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99
Q

Dynamic airway compression makes active expiration to be more dificult in patients with…

A
  • Airway obstruction

- Causes no problems in normal people

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100
Q

Increased airway resistance causes an increase in airway pressure upstream, what does this help with?

A

Helps open the airways by increasing the driving pressure between the airways and the alveolus (i.e. the pressure downstream)

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101
Q

If there is an obstruction in the airways (e.g. COPD or asthma), what happens to the driving pressure between the alveolus and airway

A
  • The pressure is lost over the obstructed segment
  • Causes a fall in airway pressure along airway downstream
  • Resulting in airway compression by the rising pleural pressure during active expiration so collapse
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102
Q

Problem of obstructed airways becomes worse if…

A

Patient also has decreased elastic recoil of lungs

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103
Q

What is the purpose of a peak flow meter?

A
  • Gives an estimate of peak flow rate which assesses airway function
  • Useful in patients with obstructive lung disease
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104
Q

How is peak flow rate measured?

A
  • Measured by giving the patient a short sharp blow into the peak flow meter
  • Best of three attempts usually taken
  • Varies with age and height
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105
Q

What is pulmonary compliance?

A

A measure of effort that has to go into stretching or distending the lungs

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106
Q

What is pulmonary compliance measured in?

A

Volume change per unit of pressure change across the lungs

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107
Q

What factors decrease pulmonary compliance?

A
  • Pulmonary fibrosis
  • Pulmonary oedema
  • Lung collapse
  • Pneumonia
  • Absence of surfactant
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108
Q

Decreased pulmonary compliance means what?

A
  • Greater change in pressure is needed to produce a given change in volume
  • Causes shortness of breath especially on exertion
  • May cause a restrictive pattern of lung volumes in spirometry
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109
Q

When may pulmonary compliance become increased?

A

If the elastic recoil of the lungs is lost

- Occurs in emphysema, patients have to work harder to get the air out of the lungs (hyperinflation of lungs)

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110
Q

Compliance increases with what?

A

Increasing age

111
Q

For quiet breathing, what percentage of total energy expenditure is required?

A

3% of total energy expenditure

112
Q

What is the phrase used to describe how lungs operate?

A

“half full”

113
Q

In what situations is work of breathing increased in?

A
  • When pulmonary compliance is decreased
  • Airway resistance increased
  • Elastic recoil decreased
  • When there is a need for increased ventilation
114
Q

What is pulmonary ventilation?

A

Volume of air breathed in and out per minute

115
Q

What is alveolar ventilation?

A

Volume of air exchanged between the atmosphere and alveoli per minute

116
Q

What is anatomical deadspace?

A

Area where air remains in the airways which is not available for gas exchange

117
Q

How is pulmonary ventilation (L) calculated?

A

Pulmonary ventilation = tidal volume (L/breath) x respiratory rate (breath/min)

118
Q

Alveolar ventilation is less than pulmonary ventilation due to the presence of…

A

Anatomical dead space

119
Q

How is alveolar ventilation calculated?

A

Alveolar ventilation

= (tidal volume - dead space volume) x respiratory rate

120
Q

To increase pulmonary ventilation…

A

Both the depth (tidal volume) and the rate of breathing (BR) increase

121
Q

Why is it more advantageous to increase the depth of breathing?

A

Because of dead space

122
Q

The transfer of gases between the body and atmosphere depends upon what two features?

A
  • Ventilation

- Perfusion

123
Q

What is perfusion?

A

The rate at which blood is passing through the lungs

124
Q

What is ventilation?

A

The rate at which gas is passing through the lungs

125
Q

What is alveolar dead space?

A

Ventilated alveolar which are not adequately perfused with blood

126
Q

What is dead space like in healthy people?

A
  • Very small dead space

- Little performance

127
Q

What is physiological dead space?

A

Anatomical dead space + alveolar dead space

128
Q

When could the alveolar dead space increase significantly?

A

In disease

129
Q

Local controls in the ventilation perfusion match in the lungs act on what?

A
  • Act on smooth muscles of airways and arterioles

- To match airflow to blood flow

130
Q

Accumulation of CO2 in alveoli can be a result of

A

Increased perfusion

131
Q

What does accumulation of CO2 in alveoli do?

A

Decreases airway resistance

Leads to increased airflow

132
Q

Increase in alveolar O2 can be a result of what?

A

Increased ventilation

133
Q

What does increase in alveolar O2 do?

A
  • Increase ventilation
  • Causes pulmonary vasodilation
  • Increased blood flow to match larger airflow
134
Q

Name the areas in which perfusion is greater than ventilation?

A
  • CO2 increases
  • O2 decreases
  • Dilation of local airways
  • Constriction of local blood vessels
  • Airflow increases
  • Blood flow decreases
135
Q

Name the areas in which ventilation is greater than perfusion?

A
  • CO2 decreases
  • O2 increases
  • Constriction of local airways
  • Dilation of local blood vessels
  • Airflow decrease
  • Blood flow increase
136
Q

What is the effect of O2 on pulmonary arterioles?

A
  • Decreased O2 means vasoconstriction

- Increased O2 means vasodilation

137
Q

What is the effect of O2 on systemic arterioles?

A
  • Decreased O2 means vasodilation

- Increased O2 means vasoconstriction

138
Q

What are the four factors that influence the rate of gas exchange across alveolar membrane?

A
  • Partial pressure gradient of O2 and CO2
  • Diffusion coefficient for O2 and CO2
  • Surface area of the alveolar membrane
  • Thickness of the alveolar membrane
139
Q

What does the partial pressure of a gas determine?

A

Determines the pressure gradient for that gas

140
Q

What is Dalton’s Law of Partial Pressures?

A

The total pressure exerted by a gaseous mixture
equals
The sum of partial pressures of each individual component in the gas mixture

141
Q

P(total) =

A

P1 + P2 + … + Pn

142
Q

What is the partial pressure of gas?

A

Pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume
Occupied by the mixture at a given temperature

143
Q

How to calculate the partial pressure of oxygen in the alveolar air

A

PAO2 = PiO2 - [PaCO2/0.8]

144
Q

What is PAO2?

A

Partial pressure of O2 in alveolar air

145
Q

What is PiO2?

A

Partial pressure of O2 in inspired air

146
Q

What is PaCO2?

A

Partial pressure of CO2 in arterial blood

147
Q

What is the 0.8 in the alveolar gas equation?

A

Respiratory exchange ratio

148
Q

The air in the respiratory tract is saturated with what?

A

Water

149
Q

What is the O2 partial pressure gradient from alveoli to blood across pulmonary capillaries?

A

60 mm Hg (8 kP)

150
Q

What is the CO2 partial pressure gradient from alveoli to blood across pulmonary capillaries?

A

6 mm Hg (0.8 kP)

151
Q

What is the O2 partial pressure gradient from blood to tissue cell across systemic capillaries?

A

> 60 mm Hg (8 kP)

152
Q

What is the CO2 partial pressure gradient from tissue cell to blood across systemic capillaries?

A

> 6 mm Hg (0.8 kP)

153
Q

The partial pressure gradient for CO2 is much ______ than that for O2

A

smaller

154
Q

What offset the difference in partial pressure gradient for CO2 and O2?

A
  • CO2 is more soluble in membranes than O2
155
Q

What is the diffusion coefficient for a gas?

A

The solubility of gas in membranes

156
Q

How much more is the diffusion coefficient for CO2 than that of O2?

A

20 times more

157
Q

How big is the gradient between alveolar PO2 (PAO2) and arterial PO2 (PaO2)?

A

Small gradient

158
Q

What would a big gradient between PAO2 and PaO2 indicate?

A
  • Problems with gas exchange in the lungs

- Right to left shunt in the heart

159
Q

What is Fick’s Law of diffusion?

A

The amount of gas that moves across a sheet of tissue in unit time is…

  • proportional to the area of the sheet
  • inversely proportional to thickness of the sheet
160
Q

The lungs have a very extensive ______ ______ network

A

Pulmonary capillary

161
Q

Remember: The pulmonary circulation receives the entire what?

A

Receives the entire cardiac output

162
Q

What are the three respiratory membranes?

A
  • Alveoli
  • Pulmonary Capillaries
  • Narrow Interstitial Space
163
Q

Name 3 non-respiratory functions of the respiratory system

A
  • Route for water loss and heat elimination
  • Enhances venous return
  • Helps maintain normal acid-base balance
  • Enables speech, singing and other vocalisations
  • Defends agains inhaled foreign matter
  • Removes, modifies, activates or inactivates various materials passing through the pulmonary circulation
  • Nose serves as the organ of smell
164
Q

What does Henry’s Law State?

A

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

165
Q

According to Henry’s law, if the partial pressure in the gas phase is increased the concentration of the gas in the liquid phase would…

A

Increase proportionally

166
Q

The partial pressure of a gas in solution is its partial pressure in the gas mixture with which it is in…

A

equilibrium

167
Q

The O2 amount dissolved in blood is proportional to what?

A

Proportional to partial pressure (Henry’s Law)

168
Q

Most O2 in the blood is transported bound to what?

A

Bound to haemoglobin in the red blood cells

169
Q

What two forms is O2 present in the blood?

A
  • Bound to haemoglobin

- Physically dissolved (very little O2)

170
Q

Haemoglobin can form a reversible combination with…

A

O2

171
Q

Each haemoglobin (Hb) molecule contains how many haem groups?

A

4 haem groups

172
Q

Haemoglobin is considered _______ _______ when all the Hb present is carrying its maximum _____ _____

A
  • Fully saturated

- O2 Load

173
Q

Each haem group ______ binds to one _____ ______

A
  • reversibly binds

- O2 molecule

174
Q

What is the Po2?

A

The primary factor which determines the percent saturation of haemoglobin with O2

175
Q

How to calculate the oxygen delivery index (DO2I)?

A

DO2I = CaO2 x CI

176
Q

What is CaO2?

A

Oxygen content of arteril blood (ml/L)

177
Q

What is CI?

A

Cardiac Index (L/min/metre^2)

178
Q

How is the oxygen delivery index (DO2I) measured?

A

ml/min/metre^2

179
Q

Cardiac index relates the cardiac output to the…

A

Body surface area

180
Q

Oxygen delivery to the tissues is a function of…

A
  • Oxygen content of arterial blood

- Cardiac output

181
Q

How do you calculate the oxygen content of arterial blood (CaO2)?

A

CaO2 = 1.34 x [HB] x SaO2

182
Q

Why 1.34 when calculating the oxygen content of arterial blood?

A

One gram of Hb carries 1.34ml of O2 when fully saturated

183
Q

What is [Hb}?

A

Haemoglobin concentration (gram/L)

184
Q

What is SaO2?

A

%Hb saturated with O2

- determined by PO2

185
Q

What determines the O2 content of arterial blood?

A
  • Determined by the haemoglobin concentration [Hb]

- Saturation of Hb with O2

186
Q

Oxygen delivery to the tissues can be impaired by what?

A
  • Respiratory disease
  • Heart failure
  • Anaemia
187
Q

How does respiratory disease decrease partial pressure of inspired oxygen?

A
  • Decrease arterial PO2
  • So decrease Hb saturation with O2
  • So decrease O2 content of the blood
188
Q

How does anaemia decrease partial pressure of inspired oxygen?

A
  • Decreases Hb concentration

- So decreases O2 content of the blood

189
Q

How does heart failure decrease partial pressure of inspired oxygen?

A
  • Decreases cardiac output
190
Q

The binding of one O2 to Hb increases the affinity of what? for what?

A

Hb for O2

191
Q

Why is the sigmoid significant?

A
  • Flat upper portions means moderate fall in alveolar Po2 will not affect oxygen loading much
  • Steep lower part means peripheral tissues get a lot of oxygen for a small drop in capillary Po2
192
Q

What is the Bohr Effect?

A
  • Decrease in oxygen affinity of haemoglobin
    In response to decreased blood pH
  • Which results from increased carbon dioxide concentration in the blood
193
Q

How does foetal haemoglobin (HbF) differ from adult haemoglobin?

A

In the structure

  • HbF has 2 ALPHA subunits
  • And 2 GAMMA subunits
194
Q

HbF interacts more/less with 2,3-Biphosphoglycerate in red blood cells

A

less

195
Q

HbF has a higher/lower affinity for O2 compared to adult haemoglobin (HbA)

A

higher

196
Q

HbF having a higher affinity for O2 than HbA means what?

A

It would allow O2 to transfer from mother to foetus even if the PO2 is low

197
Q

Myoglobin is present in what muscles?

A

Skeletal and cardiac muscles

198
Q

How many haem groups are there per myoglobin molecule?

A

One haem group per myoglobin molecule

199
Q

What is cooperative binding of oxygen?

A
  • Occurs with haemoglobin

- As oxygen binding increases, the affinity of haemoglobin for more oxygen increases

200
Q

What is increased in haemoglobin caused by?

A

A conformational or structural change in the haemoglobin molecule

201
Q

Does myoglobin have cooperative binding for O2?

A

No

202
Q

Myoglobin releases O2 at very high/low PO2

A

Low

203
Q

What does myoglobin provide for anaerobic conditions

A

Short-term storage of O2

204
Q

Presence of myoglobin in the blood indicates what?

A

Muscle damage

205
Q

Oxygen picked up by the blood must be transported in the ______ to the tissues for cellular use

A

blood

206
Q

CO2 produced at tissues must be transported in the ______ to the lungs for removal from the body

A

blood

207
Q

What are the three means of CO2 transport in the blood?

A
  • Solution (10%)
  • As Bicarbonate (60%)
  • As Carbamino Compounds (30%)
208
Q

CO2 in solution follows which law?

A

Henry’s Law

209
Q

Carbon dioxide is how many times more soluble than oxygen?

A

20 times more soluble

210
Q

What molecule forms Bicarbonate in the blood?

A

Carbonic Anhydrase

211
Q

Where does the formation of bicarbonate occur?

A

Occurs in red blood cells

212
Q

Carbamino compounds are formed by what?

A

Formed by combination of CO2 with terminal amine groups in blood proteins

213
Q

What part of haemoglobin is especially important when forming carbamino-haemoglobin

A

Globin

214
Q

Formation of carbamino compounds is rapid even without what?

A

Enzymes

215
Q

Reduced Hb can bind more _____ than _____

A

CO2 than HbO2

216
Q

What is the Haldane Effect?

A

Removing O2 from Hb increases the ability of Hb to pick-up CO2 and H+ generated by CO2

217
Q

The Boher effect and the Haldane effect work together to facilitate what?

A

O2 liberation and uptake of CO2 an H+ generated by CO2 at tissues

218
Q

The Bohr Effect facilitates the removal of O2 from haemoglobin at tissue level by shifting the O2-Hb dissociation curve to what direction?

A

To the right

219
Q

What effect is occuring when oxygen shifts CO2 dissociation curve to the right?

A

The Halden Effect

220
Q

What happens to the Hb in the lungs as they pick up O2?

A

Their ability to bind to CO2 and H+ weakens

221
Q

What is the major rhythm generator in the neural control of respiration?

A

The medulla

222
Q

Fairly normal ventilation retained if section _____ medulla, ventilation ceases if section ______ medulla

A
  • above

- below

223
Q

It is now generally believed that the breathing rhythm is generated by a network of neurons called what?

A

The Pre-Botzinger complex

224
Q

What behavior do the neurons of the Pre-Botzinger complex display?

A

Pacemaker activity

225
Q

Where are the neurons of the Pre-Botzinger complex located?

A

Near the upper end of the medullary respiratory centre

226
Q

What gives rise to inspiration?

A
  • Rhythm generated by Pre-Botzinger complex
  • Excites Dorsal respiratory group neurones (inspiratory)
  • Fire in bursts
  • Firing leads to contraction of inspiratory muscles
  • When firing stops, passive expiration occurs
227
Q

What happens during “active” expiration during hyperventilation?

A
  • Increased firing of dorsal neurones excites a second group: Ventral respiratory group neurones
    Leading to forceful expiration
228
Q

In normal, quiet breathing ventral neurones do not activate what muscles?

A

Active expiratory muscles

229
Q

The rhythm generated in the medulla can be modified by neurones located where?

A

In the pons

230
Q

Without the pneumotaxic centre what happens?

A

Breathing is prolonged inspiratory gasps with brief expiration

231
Q

What is the name that decsribes prolonged inspiratory gasps with brief expiration?

A

Apneusis

232
Q

What is the apneustic centre for?

A

Impulses from these neurones excite inspiratory area of the medulla which prolongs inspiration

233
Q

Rhythm can be modified by inputs from what?

A

Pons

234
Q

Respiratory centres are influenced by stimuli received from what receptors?

A
  • Higher brain centres
  • Stretch receptors
  • Juxtapulmonary (J) receptors
  • Joint receptors
  • Baroreceptors
  • Central chemoreceptors
  • Peripheral chemoreceptors
235
Q

Give three examples of higher brain centres

A
  • Cerebral cortex
  • Limbic system
  • Hypothalamus
236
Q

What are stretch receptors?

A
  • In the walls of bronchi and bronchioles

- Cause the inlation Herin-Breur reflex (guard against hyperinflation)

237
Q

What are the Juxtapulmonary (J) receptors?

A
  • Stimulated by pulmonary capillary congestion and pulmonary oedema
  • Also stimulated by pulmonary emboli - rapid shallow breathing
238
Q

What are joint receptors stimulated by?

A

Joint movement

239
Q

What do baroreceptors do?

A

Increase ventilatory rate in response to decreased blood pressure

240
Q

What receptors relate to the chemical control of respiration?

A
  • Central chemoreceptors

- Peripheral chemoreceptors

241
Q

What are 4 examples of involuntary modifications of breathing?

A
  • Pulmonary stretch receptors Hering-Breuer Reflex
  • Joint Receptors Reflex in Exercise
  • Stimulation of repsiratory centre by temperature, adrenalinenor impulses from cerebreal cortex
  • Cough reflex
242
Q

What are five factors that may increase ventilation during exercise?

A
  • Reflexes originating from body movement
  • Adrenaline release
  • Impulses from the cerberal cortex
  • Increase in body temperature
  • Later: accumulation of CO2 and H+ generated by active muscles
243
Q

Chemical control of respiration is an example of what feedback control system?

A

Negative Feedback Control System

244
Q

What are the controlled variables in the chemical control of respiration?

A

-The blood gas tensions (especially carbon dioxide)

245
Q

What receptors sense the values of the gas tensions?

A

Chemoreceptors

246
Q

What receptors sense tension of oxygen and carbon dioxide (and H+ concentration) in the blood?

A

Peripheral chemoreceptors

247
Q

What does the pneumotaxic centre do to inspiration when stimulated?

A

Terminates inspiration

248
Q

What does the apneustic centre do to inspiration when stimulated?

A

Excites the inspiratory area of the medulla

249
Q

When are pulmonary stretch receptors activated?

A

Activated during inspiration

250
Q

What happens when pulmonary stretch receptors are discharged?

A

Inhibits inspiration

- Hering-Breuer Reflex

251
Q

Do pulmonary stretch receptors switch off during normal respiratory cycle?

A

Unlikely

  • only activated at large&raquo_space;1litre tidal volumes
  • maybe important in newborn babies
  • may prevent over-inflation lungs during hard exercise
252
Q

What do joint receptors do?

A
  • Impulses from moving limbs reflexly increase breathing

- Contribute to increased ventilation during exercise

253
Q

Where is the cough reflex receptor located?

A

Centre in the medulla

254
Q

What is the cough reflex?

A
  • Vital part of body defence mechanisms

- Helps clear airways of dust, dirt or excessive secretions

255
Q

When is the cough reflex activated?

A

Activated by irritation of airways or tight airways

256
Q

What does afferent discharge of the cough reflex stimulate?

A
  • Short intake of breath
  • Closure of the larynx
  • Contraction of abdominal muscles (increases intra-alveolar pressure)
  • Opening of the larynx and expulsion of air at high speed
257
Q

Where are the central chemoreceptors located?

A

Near the surface of the medulla of the brainstem

258
Q

What do the chemoreceptors respond to?

A

H+ concentration of the cerebrospinal fluid (CSF)

259
Q

Cerebrospinal fluid (CSF) is separated fro the blood by what?

A

Separated by the blood brain barrier

260
Q

What is the blood brain barrier impermeable to?

A

Impermeable to H+ and HCO3-

261
Q

What can the blood brain barrier readily diffuse?

A

Readily diffuses CO2

262
Q

CSF contains less ______ than blood and hence is less ______ than blood

A
  • protein

- buffered

263
Q

What is hypoxia?

A

Body is deprived of adequate oxygen supply

264
Q

What is hypercapnia

A

Abnormally elevated carbon dioxide levels in the blood

265
Q

When is the hypoxic drive of respiration stimulated?

A

Stimulated only when arterial Po2 falls to low levels (<8.0 kPa)

266
Q

Hypoxic drive is not important in normal respiration but may become important in patients with what?

A
  • In patients with chronic CO2 retention (eg. patients with COPD)
  • Important at high altitudes
267
Q

What is hypoxia at high altitudes caused by?

A

Caused by decreased partial pressure of inspired oxygen (PiO2)

268
Q

What are the acute responses to decreased partial pressure of inspired oxygen (PiO2)?

A
  • Hyperventilation

- Increased cardiac output

269
Q

What are symptoms of acute mountain sickness?

A
  • headache
  • fatigue
  • nausea
  • tachycardia
  • dizziness
  • sleep disturbance
  • exhaustion
  • shortness of breath
  • unconsciousness
270
Q

What are the chronic adaptations to high altitudes hypoxia?

A
  • Increased RBC production
  • Increased 2,3 BPG produced within RBC
  • Increased number of capillaries
  • Increased number of mitochondria
  • Kidneys conserve acid
271
Q

What receptor does the effect of the H+ drive of respiration go through?

A

Peripheral Chemoreceptors

272
Q

What molecule does not readily cross the blood brain barrier?

A

H+

273
Q

What major role do peripheral chemoreceptors play?

A

Adjusting for acidosis caused by the addition of non-carbonic acid H+ to the blood

274
Q

What does the stimulation of the peripheral chemoreceptors by H+ cause?

A

Causes…

  • hyperventilation
  • increase in elimination of CO2 from the body (CO2 can generate H+ so its increased elimination help reduce H+ in the body) (important in acid-base balance)

1ST YR RESP (8 decks)

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