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Y1 RESPIRATORY > Physiology > Flashcards

Physiology Flashcards

1
Q

What does internal respiration refer to?

A

The intracellular mechanisms which consume O2 and produce CO2

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2
Q

What does external respiration refer to?

A

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 4 steps of external respiration?

A

Ventilation
Gas exchange (alveoli-blood)
Gas transport
Gas exchange (blood-tissues)

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4
Q

Which 3 body systems are involved in external respiration?

A

Respiratory
Cardiovascular
Haematological

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5
Q

Define ventilation

A

The mechanical process by which air is moved between the atmosphere and the alveolar air sacs

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6
Q

Air flows from a region of ___ pressure to ___ pressure

A

High, low

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7
Q

Intra-alveolar pressure must be greater than atmospheric pressure for air to flow into the lungs. True/False?

A

False

Intra-alveolar pressure must be less than atmospheric pressure, since air flows from high to low pressure

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8
Q

At constant temp, as the volume of a gas increases, the pressure exerted _____ (Boyle’s Law)

A

Decreases

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9
Q

Before inspiration, intra-alveolar pressure = atmospheric pressure. True/False?

A

True

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10
Q

Which 2 forces hold the lung and thoracic wall in close opposition?

A

Intrapleural fluid cohesiveness

Negative intrapleural pressure

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11
Q

Describe intrapleural fluid cohesiveness

A

Water molecules present in intrapleural fluid are attracted to each other/resist being pulled apart
This causes pleural membranes to stick together

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12
Q

Describe the effect of sub-atmospheric intrapleural pressure

A

Creates a transmural pressure gradient across the lung and chest wall, causing lungs to expand outwards while the chest squeezes inwards (inspiration)

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13
Q

Intra-alveolar pressure = 760
Intrapleural pressure = 756
What happens across the lung wall?

A

Lungs expand outwards

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14
Q

Intrapleural pressure = 756
Atmospheric pressure = 760
What happens across the thoracic wall?

A

Chest squeezes inwards

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15
Q

Contraction of the diaphragm causes the volume of thorax to increase in which direction?

A

Vertically

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16
Q

What is the function of external intercostal muscle in inspiration?

A

Lifts ribs up, pushes out sternum

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17
Q

What is a pneumothorax?

A

Air in the pleural space - abolishes the transmural pressure gradient needed for lung expansion

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18
Q

What is the function of surfactant?

A

Reduces alveolar surface tension

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19
Q

Smaller alveoli have a smaller tendency to collapse. True/False?

A

False

More likely to collapse - Law of LaPlace

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20
Q

What secretes surfactant?

A

Type II alveoli

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21
Q

What cause respiratory distress syndrome in new borns?

A

Not enough surfactant, leading to high alveolar surface tension

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22
Q

Describe alveolar interdependence

A

When one alveoli starts to collapse, surrounding alveoli recoil in resistance, pulling the collapsing alveoli open

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23
Q

What are the 2 main and 2 accessory muscles of respiration?

A

Diaphragm, external intercostal muscles

Scalenus, sternocleidomastoid

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24
Q

What is meant by tidal volume?

A

Volume of air entering/leaving the lungs in a single breath

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25
Q

What is meant by inspiratory reserve volume?

A

Volume of air that can be maximally inspired beyond the tidal volume

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26
Q

What is meant by inspiratory capacity?

A

TV + IRV

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27
Q

What is meant by expiratory reserve volume?

A

Volume of air that can be maximally expired beyond the tidal volume

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28
Q

What is meant by residual volume?

A

Volume of air remaining in lungs after maximal expiration

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29
Q

What is meant by functional residual capacity?

A

Volume of air remaining in lungs following normal expiration
ERV + RV

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30
Q

What is meant by vital capacity?

A

Volume of air that can be maximally expired following maximal inspiration
TV + IRV + ERV

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31
Q

What is meant by total lung capacity?

A

Maximum volume of air the lungs can hold

VC + RV

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32
Q

Residual volume can be measured with a spirometer. True/False?

A

False

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33
Q

What is meant by forced vital capacity?

A

Volume of air that can be forcefully maximally expired following maximum inspiration

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34
Q

In obstructive airways disease, FVC is low and FEV1 is low, but the FEV1/FVC ratio stays the same. True/False?

A

False FVC is normal/low, FEV1 is low, FEV1/FVC ratio is reduced

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35
Q

In restrictive airways disease, FVC is ___ and FEV1 is ___, and the FEV1/FVC ratio is ____

A

Low, low, normal

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36
Q

What is the primary determinant of resistance to airflow?

A

Radius of the conducting airway

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37
Q

Intrapleural pressure falls during expiration. True/False?

A

False

Rises during expiration; falls during inspiration

38
Q

What is meant by dynamic airway compression?

A

The rising intrapleural pressure during expiration compresses the alveoli and airway

39
Q

What is pulmonary compliance?

A

How easy/difficult it is to stretch the lungs

40
Q

Low pulmonary compliance means that the lung does not have to work as hard to inflate. True/False?

A

False

Decreased compliance means more effort isrequired to inflate the lungs

41
Q

What is anatomical dead space with regards to airways?

A

Part of the airways where gas exchange does not occur

42
Q

Pulmonary Ventilation = volume of air breathed in and out per minute = ?

A

RR x TV

43
Q

Alveolar ventilation is greater than pulmonary ventilation. True/False?

A

False

It is less than pulmonary ventilation due to dead space

44
Q

Define alveolar ventilation

A

Volume of air exchanged between the atmosphere and alveoli per minute

45
Q

How can pulmonary ventilation be increased?

A

Increase the depth of breathing

Increase the respiratory rate

46
Q

Blood flow is faster at the top of the lungs. True/False?

A

False

Faster at the bottom

47
Q

V/Q ratio is better at the top of the lungs. True/False?

A

True

48
Q

Accumulation of CO2 as a result of _____ perfusion leads to _____ airflow (by _____ airflow resistance)

A

Increased, increased, decreasing

49
Q

Accumulation of O2 as a result of ____ ventilation leads to pulmonary vaso____

A

Increased, vasodilation

50
Q

What are the 4 factors which influence the rate of gas exchange across the alveolar membrane?

A

Partial pressures of O2 and CO2
Diffusion coefficient of O2 and CO2
Surface area of membrane
Thickness of membrane

51
Q

The partial pressure of O2 is less than the partial pressure of CO2. True/False?

A

False

52
Q

What is the diffusion coefficient of a gas?

A

The solubility of the gas in membranes

53
Q

The diffusion coefficient of CO2 is __ times that of O2

A

20

54
Q

The amount of gas that will dissolve in a given volume is proportional to the ________ of the gas at equilibrium within the liquid (Henry’s Law)

A

Partial pressure

55
Q

If the partial pressure is increased, less gas will dissolve. True/False?

A

False

More gas will dissolve

56
Q

PO2 is normally ___ mm Hg (___ kPa)

A

100 mm Hg, 13.3 kPa

57
Q

Most O2 is transported in the blood in the dissolved form. True/False?

A

False

Most is bound to haemoglobin

58
Q

How many haem groups does one haemoglobin molecule contain?

A

4

59
Q

What is the primary determination of haemoglobin O2 saturation?

A

PO2

60
Q

When the concn of haemoglobin is decreased, what happens to oxygen saturation? Why?

A

Stays the sameRemaining haemoglobin is still fully saturated as PO2 remains the same, but less haemoglobin means there is less oxygen being carried in total - but saturations are normal!

61
Q

Binding of one O2 to haemoglobin increases affinity of Hb for O2. True/False? This is known as…

A

True

Cooperativity

62
Q

What is the Bohr Effect?

A

Increased release of O2 from Hb at tissues (sigmoid shifts to right)

63
Q

Where is myoglobin mainly present?

A

Skeletal and cardiac muscle

64
Q

What shape is the dissociation curve for myoglobin and oxygen?

A

Hyperbolic

65
Q

Presence of myoglobin in the blood indicates what?

A

Muscle damage

66
Q

What are the 3 methods of CO2 transport in the blood?

A

Solution
As bicarbonate
As carbamino compounds

67
Q

Most CO2 is transported in the blood as what?

A

Bicarbonate

68
Q

Which enzyme catalyses formation of bicarbonate?

A

Carbonic anhydrase in RBCs

69
Q

Where does CO2 bind on haemoglobin to form carbaminohaemoglobin?

A

Globin part

70
Q

Reduced Hb binds more CO2 than HbO2. True/False?

A

True

71
Q

What is the Haldane Effect?

A

Removing O2 from Hb increases Hb’s affinity for CO2 and CO2-generated H+i.e. O2 will be released at tissues; this will increase affinity of Hb for CO2; thus CO2 will be taken up from tissues!

72
Q

Which part of the brain is the main rhythm generator of breathing?

A

Medulla

73
Q

The breathing rhythm is generated by a group of neurones called the ________

A

Pre-Botzinger Complex

74
Q

Where is the Pre-Botzinger Complex located?

A

Upper end of medulla

75
Q

Inspiration is caused by firing of which neurones?

A

Dorsal respiratory group neurones

76
Q

When are ventral respiratory group neurones fired? What do they excite?

A

In active expiration (hyperventilation) after increased firing of dorsal respiratory group neurones
Excite secondary muscles of respiration

77
Q

The rhythm generated in the medulla can be modified by neurones in what other part of the brain?

A

Pons

78
Q

What is the function of the Pneumotaxic Centre in the pons?

A

Inhibits inspiration; stimulated when dorsal respiratory group neurones fire

79
Q

What is the function of the Apneustic Centre in the pons?

A

Prolong inspiration; impulses from here excite the inspiratory area of the medulla

80
Q

Stretch receptors can influence the respiratory centres in the brain. What do they do and guard against?

A

Inhibit inspiration

Guard against overinflation of lungs

81
Q

Joint receptors influence respiratory centres in the brain, how?

A

Moving limbs leads to increased breathing

82
Q

What is the function of chemoreceptors?

A

Sense values of gas/chemical tensions

83
Q

Chemoreceptors which sense tension of O2, CO2 and [H+] in the blood

A

Peripheral chemoreceptors

84
Q

Where are peripheral chemoreceptors located?

A

Carotid + aortic bodies

85
Q

Chemoreceptors which sense the [H+] of the CSF

A

Central chemoreceptors

86
Q

Where are central chemoreceptors located?

A

Near the medulla

87
Q

What separates CSF from blood?

A

Blood-brain barrier

88
Q

CO2 and [H+] diffuse readily across the blood-brain barrier. True/False?

A

False

Only CO2 diffuses readily

89
Q

Stimulation of peripheral chemoreceptors (by [H+]) causes hypoventilation and CO2 retention. True/False?

A

False

Hyperventilation and CO2 elimination

90
Q

What is Ficks Law of Diffusion?

A

Amount of gas that moves across sheet in unit time is proportional to surface area of sheet but inversely proportional to its thickness

91
Q

What is the difference between foetal haemoglobin and adult haemoglobin?

A

It has an increased affinity for O2

Y1 RESPIRATORY (12 decks)

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