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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

What are the two types of respiration?

A

Internal & External

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2
Q

What is internal respiration?

A

the intracellular mechanisms which consume oxygen and produce carbon dioxide

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3
Q

What is external respiration?

A

the sequence of events that lead to the exchange of oxygen and carbon dioxide between the environment and the body cells

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4
Q

State the four steps of external respiration

A
  1. Ventilation
  2. Gas exchange
  3. Transport in the blood
  4. Exchange at tissue level
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5
Q

Name four systems involved in external respiration

A
  • Respiratory
  • Cardiovascular
  • Haematology
  • Nervous
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6
Q

What is ventilation?

A

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

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7
Q

State Boyle’s Law

A

At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas. As the volume of the gas increases the pressure decreases

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8
Q

Describe the pressure difference before inspiration

A

The intra-alveolar pressure is equivalent to the atmospheric pressure

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9
Q

Describe the pressure difference during inspiration

A

The intra-alveolar pressure becomes less than atmospheric pressure so air flows down the gradient and into the lungs

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10
Q

State two ways in which the lungs are linked to the thorax

A
  1. Intra-pleural fluid cohesiveness

2. Negative intra-pleural pressure

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11
Q

Describe intra-pleural fluid cohesiveness

A

The water molecules are attracted to each other and resist being pulled apart

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12
Q

Describe negative intra-pleural pressure

A

The sub atmospheric intra-pleural pressure creates a transmural pressure gradient across the lung and chest walls. So the lungs are forced to expand outwards while the chest is forced to squeeze inwards

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13
Q

How do you convert mmHg to kPa?

A

divide by 7.5

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14
Q

Is inspiration an active or passive process?

A

Active (depends on muscle contraction)

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15
Q

How does the thorax volume change during inspiration?

A

It is increased vertically by the contraction of the diaphragm flattening out its dome shape.

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16
Q

What is the role of the external intercostal muscles during inspiration?

A

They contract to lift the ribs and move the sternum out.

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17
Q

Explain the pressure change during inspiration

A

The increase in size of the lungs makes the intra alveolar pressure decrease. This is because the air molecules become contained in a larger volume. The air moves down its pressure gradient into the lungs.

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18
Q

Is expiration an active or passive process?

A

passive (brought about by relaxation of inspiratory muscles)

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19
Q

Describe the pressure change during expiration

A

The molecules are in a smaller volume so the pressure increases and the air moves down its gradient out of the lungs

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20
Q

Define pneumothorax

A

Air in the pleural space

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21
Q

Name three causes of a pneumothorax

A
  • spontaneous
  • traumatic
  • iatrogenic
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22
Q

What happens to the transmural pressure gradient as a result of a pneumothorax?

A

It is abolished and this leads to a collapsed lung

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23
Q

What are the symptoms of a pneumothorax?

A

shortness of breath & chest pain

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24
Q

What are the signs of a pneumothorax?

A

hyper-resonant percussion note & decreased/absent breath sounds

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25
Q

Name two factors that contribute to lung recoil

A
  • elastic connective tissue

- alveolar surface tension

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26
Q

Describe alveolar surface tension

A

attraction between water molecules at liquid air interface produces a force which resists the stretching of the lungs

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27
Q

What compound reduces surface tension?

A

Surfactant - mixture of lipids and proteins secreted by type II alveoli

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28
Q

According to the law of LaPlace what happens to smaller alveoli ?

A

They have a higher tendency to collapse

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29
Q

What does surfactant do?

A

Reduces the surface tension and prevents the small alveoli from collapsing & emptying their contents into the larger alveoli

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30
Q

Explain what is meant by alveolar interdependence

A

If an alveolus starts to collapse the surrounding alveoli are stretched and then recoil exerting expanding forces on the collapsing alveolus to open it.

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31
Q

What are the muscles of inspiration?

A

Major - diaphragm & external intercostal muscles

Accessory - sternocleidomastoid, scalenus, pectoral

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32
Q

What are the muscles of expiration?

A

Abdominal & internal intercostal muscles

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33
Q

What is tidal volume?

A

Air in/out in a single breath - 0.5L

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34
Q

What is inspiratory reserve volume?

A

Extra volume that can be maximally inspired above the typical resting tidal volume - 3.0L

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35
Q

What is expiratory reserve volume?

A

Extra volume that can be expired by maximal contraction - 1L

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36
Q

What is residual volume?

A

Minimum volume of air remaining after maximal expiration - 1.2L

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37
Q

What is inspiratory capacity?

A

Maximum volume of air that can be inspired at the end of a normal quiet expiration 3.5L

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38
Q

What is functional residual capacity?

A

volume of air in the lungs at the end of normal passive expiration - 2.2L

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39
Q

What is vital capacity?

A

maximum volume of air that can be moved out during a single breath following maximal inspiration - 4.5L

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40
Q

What is total lung capacity?

A

total volume of air that the lungs can hold c. 5.7L

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41
Q

What happens to the elastic recoil when residual volume increases?

A

Recoil is lost e.g. emphysema

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42
Q

State the difference between FVC and FEV1

A

FVC - forced vital capacity (maximum volume expelled from the lungs)
FEV1 - forced expiratory volume in 1 second (volume expired in the first second of expiration)

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43
Q

What should FEV/FVC be greater than?

A

70%

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44
Q

How do you calculate flow?

A

change in pressure/resistance

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45
Q

Describe airway resistance

A

It is usually low and so air moves with a small pressure gradient. The primary determinant is the radium of the conducting airway

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46
Q

What does para/sympathetic stimulation do?

A

parasympathetic - bronchocontriction

sympathetic - bronchodilatation

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47
Q

What is peak flow?

A

The speed at which someone can get air out of the lungs

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48
Q

What is pulmonary compliance?

A

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

49
Q

State five factors that decrease compliance

A
  • pulmonary fibrosis
  • pulmonary oedema
  • collapsed lung
  • pneumonia
  • absence of surfactant
50
Q

What is the effect of decreased compliance ?

A

Greater change in pressure is needed to produce a given change in volume and this causes shortness of breath

51
Q

How is compliance increased?

A

By loss of elastic recoil in emphysema.

52
Q

What is emphysema?

A

Narrowing of the alveoli

53
Q

When is the work of breathing increased?

A
  • decrease in compliance
  • increase in airway resistance
  • decrease in elastic recoil
  • increase in need for ventilation
54
Q

How do you calculate pulmonary ventilation?

A

tidal volume x respiratory rate

55
Q

Define pulmonary ventilation

A

the volume of air breathed in and out per minute

56
Q

How do you calculate alveolar ventilation?

A

(tidal volume - dead space) x respiratory rate

57
Q

Define alveolar ventilation

A

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

58
Q

why is alveolar ventilation less than pulmonary ventilation?

A

Because of the presence of anatomical dead space

59
Q

How can pulmonary ventilation be increased?

A

By increasing depth and rate of breathing

60
Q

What two process does the transfer of gas between the body and atmosphere depend on?

A

Ventilation & Perfusion

61
Q

Explain the difference between ventilation and perfusion

A

ventilation is the rate at which gas passes through the lungs whereas perfusion is the rate at which blood passes through the lungs

62
Q

Describe alveolar dead space

A

Ventilated alveoli which are not adequately perfused with blood. In healthy people this is usually small and not important

63
Q

State six things that happen when perfusion is greater than ventilation

A
  • carbon dioxide increased in the area
  • dilatation of local airways
  • airflow increases
  • oxygen decreases in the area
  • constriction of local blood vessels
  • blood flow decreases
64
Q

State six things that happen when ventilation is greater than perfusion

A
  • carbon dioxide decreases in the area
  • constriction of local airways
  • airflow decreases
  • oxygen increases in the area
  • dilatation of local blood vessels
  • blood flow increases
65
Q

Name four factors that influence the rate of gas exchange

A
  • partial pressure gradient of oxygen and carbon dioxide
  • diffusion coefficient for oxygen and carbon dioxide
  • surface area of alveolar membrane
  • thickness of alveolar membrane
66
Q

Define partial pressure

A

the 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

67
Q

Define diffusion coefficient

A

the solubility of gas in membranes

68
Q

What are some other functions of the respiratory system?

A
  • route for water loss/heat elimination
  • enhances venous return
  • helps maintain normal acid-base balance
  • enables speech, singing and other vocalisations
  • defends against inhaled foreign matter
  • nose serves as the organ of smell
69
Q

What is Henry’s Law?

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

70
Q

Under resting conditions & strenuous exercise how much oxygen is taken to the tissues in dissolved form

A

15ml/min & 90ml/min

71
Q

What is the resting oxygen consumption of our body cells?

A

250ml/min

72
Q

How is most of the oxygen in the blood transported?

A

Bound to haemoglobin in red blood cells

73
Q

What is the normal oxygen & haemoglobin concentration?

A

oxygen - 200ml/litre

haemoglobin - 150g/litre

74
Q

Describe the binding of oxygen to haemoglobin

A

Each Hb has four haem groups and a protein. When one oxygen binds this increases the affinity of oxygen for the other subunits. Hb is considered to be fully saturated when all groups are filled.

75
Q

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

A

partial pressure

76
Q

What shape is the curve produced which relates partial pressure to %Hb/oxygen concentration?

A

Sigmoid

77
Q

Where can myoglobin be found?

A

Skeletal and cardiac muscles

78
Q

What shape is the myoglobin dissociation curve what can be said about the affinity?

A

It is a hyperbolic curve and it has a higher affinity than haemoglobin but no cooperative binding

79
Q

What does oxygen delivery to the tissues depend on?

A

Oxygen content of arterial blood

Cardiac Output

80
Q

What determines the oxygen content of arterial blood?

A

haemoglobin concentration

saturation of Hb with oxygen

81
Q

Name three ways by which oxygen delivery can be impaired

A
  • respiratory disease
  • heart failure
  • anaemia
82
Q

How is carbon dioxide transported?

A

10% solution
60% bicarbonate
30% carbamino compounds

83
Q

Describe carbon dioxide in solution

A

The amount of gas dissolved is independent on the partial pressure. Carbon dioxide is 20x more soluble than oxygen

84
Q

How is bicarbonate formed in the blood?

A

carbon dioxide + water –> Carbonic acid –> hydrogen ions + carbonate ions

85
Q

What enzyme is invalid in bicarbonate formation? Where is bicarbonate found?

A

Carbonic anhydrase in red blood cells

86
Q

Describe the movement of carbonate by the chloride shift

A

Carbonate is exchanged for chloride ions. The carbonate ion moves out of the red blood cell and chlorine moves in.

87
Q

How are carbamino compounds formed?

A

By the combination of carbon dioxide with terminal amine groups in blood proteins.

88
Q

What is the major blood protein that carbon dioxide binds to?

A

globin in haemoglobin

89
Q

What is the Haldane Effect?

A

removing oxygen from Hb increases the ability to pick-up carbon dioxide and carbon dioxide generated hydrogen ions.

90
Q

What is the Boher Effect?

A

removing the carbon dioxide/hydrogen ions from Hb increases the ability to pick-up oxygen

91
Q

Define the rhythm

A

inspiration followed by expiration

92
Q

Where is breathing rhythm generated?

A

Pre-Botzinger Complex

93
Q

What is the Pre-Botzinger Complex?

A

Network of neutrons that display pacemaker activity, they are located near the upper end of the medullary respiratory centre

94
Q

What does the pre-botzinger complex do?

A

Excites dorsal respiratory group neurones, leading to contraction of inspiratory muscles

95
Q

What happens when firing of the dorsal group neurones stops?

A

Passive expiration occurs

96
Q

Name the second group of neurones involved in respiration

A

Ventral respiratory group

97
Q

How are the ventral respiratory group excited?

A

By increased firing of dorsal neurones

98
Q

What happens as a result of excitation of the ventral group?

A

Forceful expiration, not in normal quiet breathing

99
Q

How can the rhythm generated in the medulla be modified?

A

Neurones in the pons

  • pneumotaxic centre
  • apneustic centre
100
Q

Describe the pneumotaxic centre, what happens without it?

A

stimulation terminates inspiration when dorsal respiratory neurones fire. Without it breathing is prolonged inspiratory gasps with brief expiration

101
Q

Describe the apneustic centre

A

impulses from these neurones excite the inspiratory area of the medulla and prolong inspiration

102
Q

where can stimuli that influence respiratory centres be found?

A
  • higher brain centres
  • stretch receptors
  • J receptors
  • joint receptors
  • baroreceptors
  • central chemoreceptors
  • peripheral chemoreceptors
103
Q

Give four examples of involuntary modifications of breathing

A
  • pulmonary stretch receptors
  • joint receptors reflex in exercise
  • stimulation of respiratory centre by temperature, adrenaline or impulses
  • cough reflex
104
Q

Describe pulmonary stretch receptors

A

Activated during inspiration, afferent discharge inhibits inspiration. They do not switch off during normal respiration so prevent hyperinflation of the lungs

105
Q

Describe joint receptors

A

impulses from moving limbs reflex increases breathing. They contribute to increased ventilation during exercise

106
Q

name five factors that increase ventilation during exercise

A
  1. relflexes
  2. adrenaline release
  3. impulses from cerebral cortex
  4. increased body temperature
  5. accumulation of carbon dioxide and hydrogen ions
107
Q

Describe the cough reflex

A

Helps to clear airways, it is activated by irritation of airways. Afferent discharge stimulates a short intake in breath followed by closure of the larynx then contraction of abdominal muscles and finally opening of the larynx and expulsion of air at high speed

108
Q

Where is the cough reflex centre?

A

medulla

109
Q

What are the two types of control of the respiratory system?

A

Neural

Chemical

110
Q

What are the two types of chemoreceptor?

A
  • Peripheral

- Central

111
Q

Describe the peripheral chemoreceptors

A

in carotid & aortic bodies they sense tension of oxygen, carbon dioxide and concentration of hydrogen ions in the blood

112
Q

Describe central chemoreceptors

A

near the surface of the medulla they respond to hydrogen ion concentration of the cerebrospinal fluid

113
Q

What is the blood brain barrier?

A

relatively impermeable to hydrogen ions and carbonate ions, carbon dioxide readily diffuses

114
Q

How does the CSF compare to blood?

A

It has less proteins and hence is less buffered

115
Q

What happens when hypoxia occurs?

A

Neurones are depressed, the effect is via the peripheral chemoreceptors which are only stimulated when arterial oxygen falls to low levels

116
Q

When might hypoxia occur?

A
  • Patients with chronic carbon dioxide retention

- High altitudes

117
Q

What are the symptoms of altitude sickness>

A 
Headache 
Fever
Fatigue 
Nausea 
Tachycardia 
Dizziness 
SOB 
Unconsciousness
118
Q

Name five adaptations to high altitude

A
  • increased RBCs
  • increased 2,3 biphosphoglycerate
  • increased number of capillaries
  • increased number of mitochondria
  • kidneys conserve acid to decrease arterial pH
119
Q

Describe hydrogen ion drive

A

Central chemoreceptors are stimulated by hydrogen ions causing hyperventilation and increased elimination of carbon dioxide to adjust acidosis

Respiratory (20 decks)

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