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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

What are the four steps of external respiration?

A

Ventilation
Gas exchange between alveoli and blood
Gas transport in the blood
Gas exchange at tissue level

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2
Q

What is ventilation?

A

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

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3
Q

What does Boyle’s law state?

A

As the volume of a gas increases the pressure exerted by the gas decreases
(At a constant temperature)

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4
Q

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

A

The intrapleural fluid cohesiveness

The negative intrapleural pressure

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5
Q

How does the intrapleural fluid cohesiveness hold the thoracic wall and the lungs in close opposition?

A

The water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart - this holds the pleural membranes together

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6
Q

How does the negative intrapleural pressure hold the thoracic wall and the lungs in close opposition?

A

The sub-atmospheric intrapleural pressure creates a transmural pressure gradient across the lung wall and across the chest wall
I.e. the pressure is lowest in the pleural cavity

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7
Q

What three pressures are important in ventilation?

A

Atmospheric pressure
Intra-alveolar pressure
Intrapleural pressure

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8
Q

What does the external intercostal muscle do during inspiration?

A

Contracts to lift the ribs and move out the sternum

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9
Q

How is the volume of the thorax increased vertically during inspiration?

A

Contraction of the diaphragm - this flattens out its dome shape

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10
Q

What does the increase in size of the lungs do to the intra-alveolar pressure?

A

Causes it to drop

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11
Q

What does the drop in intrathoracic pressure during inspiration result in?

A

Air entering the lungs by following a pressure gradient

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12
Q

Is expiration a passive or active process?

A

Passive

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13
Q

How is expiration brought about?

A

Relaxation of inspiratory muscles - the chest wall and stretched lungs recoil to their preinspiratory size because of their elastic properties

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14
Q

What does the recoiling of the lungs do to the intra-alveolar pressure?

A

Causes it to rise

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15
Q

What does the rise in intrathoracic pressure during expiration result in?

A

Air passes out of the lungs by following a pressure gradient

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16
Q

What causes the lungs to recoil during expiration?

A

Elastic connective tissue in the lungs

Alveolar surface tension

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17
Q

What is the alveolar surface tension?

A

The attraction between water molecules at liquid air interface i.e. the walls of the alveoli
This produces a force which resists the stretching of the lungs

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18
Q

What would happen to the alveoli if they were lined with water alone?

A

The surface tension would be too strong and the lung would collapse

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19
Q

What chemical is present to reduce alveolar surface tension?

A

Surfactant

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20
Q

What does the law of Laplace state?

A

The small alveoli i.e. the alveoli with smaller radius have a higher tendency to collapse

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21
Q

How does surfactant reduce the alveolar surface tension and which alveoli does it have more of an effect on?

A

Intersperses between the water molecules lining the alveoli

Lowers the surface tension of smaller alveoli more

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22
Q

What is alveolar interdependence?

A

If an alveolus starts to collapse the surrounding alveoli are stretched, and then recoil: this exerts expanding forces in the collapsing alveolus to open it

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23
Q

What is the tidal volume?

A

The volume of air entering or leaving the lungs in a normal breath (500ml)

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24
Q

What is the inspiratory reserve volume?

A

Extra volume of air which can be inspired over and above the resting tidal volume (3000ml)

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25
Q

What is the inspiratory capacity?

A

The inspiratory reseve volume and the tidal capacity (3500ml)

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26
Q

What is the expiratory reserve volume?

A

The extra volume of air that can be actively expired beyond the normal tidal volume (1000ml)

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27
Q

What is the residual volume?

A

The minimum volume of air remaining in the lungs even after a maximal expiration (this is to keep them patent) (1200ml)

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28
Q

What is the functional residual capacity?

A

The volume of air in the lungs after normal tidal expiration i.e. residual volume + expiratory reserve volume (2200ml)

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29
Q

What is the vital capacity?

A

The maximum volume of air that can be expired after a maximal inspiration i.e. ERV + TV + IRV (4500ml)

30
Q

What is the total lung capacity?

A

The maximum volume of air that the lungs can hold (RV + VC) (5700ml)

31
Q

What changes in spirometry will occur in obstructive lung disease?

A

FVC normal, FEV1 reduced, FEV1/FVC reduced

32
Q

What changes in spirometry will occur in restrictive lung disease?

A

FVC reduced, FEV1 reduced, FEV1/FVC normal

33
Q

What changes in spirometry will occur in a combination of obstructive and restrictive lung disease?

A

FVC reduced, FEV1 reduced, FEV1/FVC reduced

34
Q

What is pulmonary compliance?

A

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

35
Q

What factors decrease pulmonary compliance?

A 
Pulmonary fibrosis
Pulmonary oedema
Lung collapse
Pneumonia
Absence of surfactant
36
Q

Why does decreased pulmonary compliance result in shortness of breath?

A

A greater change in pressure is needed to produce a given change in volume - the lungs are stiffer

37
Q

When might pulmonary compliance become abnormally increased?

A

If the elastic recoil of the lungs is lost e.g. in emphysema

38
Q

What is anatomical dead space?

A

The inspired air that remains in the airways and is not available for gas exchange

39
Q

How can pulmonary ventilation be calculated?

A

Tidal volume x respiratory rate

40
Q

Why is alveolar ventilation less than pulmonary ventilation?

A

Because of the presence of anatomical dead space

41
Q

How can alveolar ventilation be calculated?

A

(Tidal volume - dead space) x respiratory rate

42
Q

What is the definition of pulmonary ventilation?

A

The volume of air breathed out and in per minute

43
Q

What is the definition of alveolar ventilation?

A

The volume of air exchanged between the atmosphere and alveoli per minute

44
Q

To increase pulmonary ventilation, what is the most useful thing to do and why?

A

Increase the depth of breathing because of dead space

45
Q

What is the definition of perfusion?

A

The rate at which blood is passing through the lungs

46
Q

What is the V/Q ratio at the bottom of the lung?

A

Blood flow > ventilation

47
Q

What is the V/Q ratio at the top of the lung?

A

Ventilation > blood flow

48
Q

What is alveolar dead space?

A

Ventilated alveoli which are not adequately perfused with blood

49
Q

What is the physiological dead space?

A

The anatomical dead space + the alveolar dead space

50
Q

What physiological response does an increase of CO2 in an alveoli (due to increased perfusion) trigger?

A

Relaxation of airway smooth muscle
Dilation of local airways
This decreases airway resistance which results in increased airflow to the affected alveoli

51
Q

What physiological response does a decrease in O2 in an alveoli (due to decreased ventilation) trigger?

A

Contraction of local pulmonary arteriolar smooth muscle
Constriction of local blood vessels
Increased vascular resistance
Decreased blood flow

52
Q

Why would an increase in O2 in an alveoli result in increased local pulmonary blood flow?

A

To balance up the V/Q mismatch that has occurred and to oxygenate as much blood as possible

53
Q

What is the diffusion coefficient of a gas?

A

The solubility of the gas in membranes

54
Q

How is most oxygen transported in the blood?

A

Bound to haemoglobin

55
Q

In what two forms is oxygen present in blood?

A

Dissolved in blood

Bound to haemoglobin

56
Q

What might shift the oxygen-haemoglobin dissociation curve to the right?

A

An increase in PCO
An increase in [H+]
An increase in temperature
An increase in 2,3-bisphosphoglycerate

57
Q

What shape is the oxygen-haemoglobin dissociation curve?

A

Sigmoid

58
Q

What shape is the oxygen-myoglobin dissociation curve?

A

Hyperbolic

59
Q

How is CO2 transported in the blood?

A

In solution
As bicarbonate - main form of transport
As carbamino compounds

60
Q

Where does the formation of bicarbonate in the blood take place?

A

Red blood cells

61
Q

What enzyme facilitates the formation of bicarbonate in blood?

A

Carbonic anhydrase

62
Q

How are carbamino compounds formed?

A

Combination of CO2 with terminal amine groups in blood proteins

63
Q

Where is the breathing rhythm generated?

A

A network of neurones called the pre-botzinger complex

64
Q

Where is the pre-botzinger complex generated?

A

The upper end of the medullary respiratory centre

65
Q

Where is the impulse for inspiration generated?

A

The dorsal group of neurones in the medulla

66
Q

What happens during hyperventilation when there is increased firing from the dorsal group of neurones?

A

The ventral respiratory group neurones are activated which excite internal intercostal muscles, abdominal muscles etc.

67
Q

What is the pneumotaxic centre?

A

An area in the pons which can modify the respiratory rhythm generated in the medulla

68
Q

What does stimulation of the pneumotaxic centre do?

A

Terminates inspiration

69
Q

What is the apneustic centre?

A

An area in the pons which can modify the respiratory rhythm generated by the medulla

70
Q

What does stimulation of the apneustic centre do??

A

Prolongs inspiration

71
Q

When are pulmonary stretch receptors activated and what is this reflex called?

A

During inspiration

Hering-Breuer reflex

72
Q

How does joint movement modify breathing?

A

Impulses from moving limbs reflexively increase breathing

Respiratory (16 decks)

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