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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

What is internal respiration?

A

Intracellular mechanisms that consume O2 and produce CO2

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2
Q

What is external respiration?

A

Exchange of O2 and CO2 between the external environment and cells

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3
Q

What are the 4 steps of external respiration?

A
  1. Ventilation
  2. Gas exchange between alveoli and blood
  3. Gas transport in the blood
  4. Gas exchange at the tissues
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4
Q

What body systems are involved with external respiration?

A

Respiratory
Cardiovascular
Haematology
Nervous

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5
Q

What is ventilation?

A

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

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6
Q

Boyle’s Law means…

A

As the volume of the lungs increases, the pressure of gas inside the lungs decreases

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7
Q

How do the thorax and lungs expand during inspiration?

A

Contraction of inspiratory muscles

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8
Q

What must the pressure conditions be for air to flow into the lungs?

A

Intra-alveolar pressure must be lower than the atmospheric pressure

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9
Q

What 2 forces hold the lungs to the thoracic wall?

A
  1. Intrapleural fluid cohesiveness

2. Negative intrapleural pressure

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10
Q

What is the average pressure of atmosphere?

A

760 mmHg

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11
Q

What is the average pressure of intra-alveolar

A

760 mmHg

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12
Q

How would you describe the relative intrapleural pressure

A

sub atmospheric

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13
Q

What kind of process is inspiration?

A

Active

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14
Q

What kind of process is expiration?

A

Passive

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15
Q

What is the transmural gradient?

A

difference in pressure between two sides of thoracic wall

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16
Q

Define pneumothorax and list the three main common causes

A

Accumulation of air in pleural space

  1. Traumatic
  2. Spontaneous
  3. Iatrogenic
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17
Q

How does a pneumothorax effect transmural pressure gradient?

A

Abolishes transmural pressure gradient- can cause lung collapse.

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18
Q

what are the signs of a pneumothorax?

A

Hyper-resonant percussion note

Decreased/absent breath sounds

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19
Q

What are the symptoms of a pneumothorax?

A

Shortness of breath

Chest pain

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20
Q

what causes lungs to recoil?

A

Elastic CT

Alveolar surface tension

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21
Q

What is surfactant and it’s function?

A

Surfactant is a complex mix secreted by type II alveoli

It’s function is to lower surface tension by interspersing between the H2O molecules lining the alveoli

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22
Q

What causes respiratory distress syndrome in newborns? especially preterm babies?

A

Often not sufficient supply of surfactant, as produced late in pregnancy

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23
Q

What alveolar interdependence?

A

The mechanism of surrounding alveoli helping to open collapsed alveoli (using expanding forces)

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24
Q

What is the order of rhythm of respiration?

A

Inspiration, expiration

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25
Q

what is the major rhythm generator?

A

The medulla

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26
Q

What neuron network is believed to generate breathing rhythm?
(spontaneous action potentials)

A

Pre-Botzinger complex
(near upper end of medullary respiratory centre)

(previously believed to be the dorsal respiratory group)

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27
Q

what group of neurones are excited by the pre-botzinger complex?

A

Dorsal respiratory group neurones

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28
Q

What does firing of nerve signals do?

A

Leads to contraction of inspiratory muscles

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29
Q

which direction will the thorax increase by contraction of the diaphragm?

A

Vertically

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30
Q

which nerve signals to the diaphragm to contract?

A

Phrenic nerve

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31
Q

What do ventral respiratory group muscles do?

A

Activate expiratory neurones during hyperventilation (active expiration)

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32
Q

Where are the neurones modifying the medulla located?

A

The pons

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33
Q

stimulation of which area terminates inspiration?

A

Pneumotaxic centre (PC)

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34
Q

which respiratory neurones stimulate the PC?

A

dorsal respiratory neurones

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35
Q

what is apneusis?

A

prolonged inspiratory gasps followed by brief expiration- happens without PC

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36
Q

what does the apneustic centre do?

A

sends out neuron impulses to excite inspiratory area of medulla

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37
Q

What stimuli can influence respiratory centres?

A 
Higher brain centres
Stretch receptors in bronchi and bronchioles (Hering-Breur reflex)
Juxtapulmonary receptors
Joint receptors
Baroreceptors (regulate BP)
Central chemoreceptors
Peripheral chemoreceptors
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38
Q

what is the hering- breur reflex?

A

a guard against hyperinflation in the bronchi and bronchioles by stretch receptors

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39
Q

What do joint receptors do?

A

send impulses from moving limbs to reflexly increase breathing

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40
Q

what are the likely receptors to contribute to increased ventilation in exercise?

A

Joint receptors

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41
Q

what are the likely factors that increase ventilation in exercise?

A 
Reflexes from body movement
Adrenaline release
Impluses from cerebral cortex
increase in body temp
accumulation of CO2 and H+ in active muscles
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42
Q

Recovery stage of ventilatory response to stimuli is a result of?

A

removal of stimulant

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43
Q

what is the function of a cough reflex?

A

To remove dust, dirt or excessive secretions from the airway

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44
Q

what activates cough reflex?

A

irritation of airways or tight airways (asthma/tumour)

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45
Q

where is the cough receptor centre)

A

medulla

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46
Q

what are the physiological steps of coughing?

A

Short breath intake
Closure of larynx
contraction of abdominal muscles (increase alveolar pressure)
opening of larynx and rapid expulsion of air

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47
Q

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

A

negative

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48
Q

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

A

blood gas tensions (esp. CO2)

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49
Q

what molecules sense the values of gas tensions?

A

Chemoreceptors

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50
Q

where are central chemoreceptors situated?

A

medulla

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51
Q

what do central chemoreceptors respond to?

A

H+ concentration of cerebrospinal fluid

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52
Q

What separates CSF from the blood?

A

blood-brain barrier

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53
Q

which gasses readily diffuse over the blood-brain barrier?

A

CO2

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54
Q

How is CSF less buffered than blood?

A

it contains less protein than blood

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55
Q

what is hypercapnia?

A

increased CO2

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56
Q

Ventilation is very sensitive to which gas?

A

CO2

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57
Q

what helps CO2 generate H+

A

central chemoreceptors

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58
Q

what is the normal arterial PO2 in a person?

A

13.3 kPa

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59
Q

What effect does hypoxia have on CNS neurones?

A

It depresses them

60
Q

at which PO2 values are the peripheral chemoreceptors stimulates?

A

> 8 kPa

61
Q

when does hypoxic drive become important?

A

Patients with chronic CO2 retention (eg. COPD)

At high altitudes

62
Q

What is hypoxia at high altitudes caused by>

A

decreased PiO2

63
Q

what are the accute responses of hypoxia at high altitudes?

A

Hyperventilation & increased cardiac output

64
Q

symptoms of acute mountain sickness

A 
headache
fatihue
nausia
tachycardia
dizziness
sleep disturbance
exhaustion
shortness of breath
unconsciousness
65
Q

chronic adaptions to high altitudes hypoxia

A 
increased RBC production (polycythaemia)
increased 2,3 BPG produced in RBCs
increased no. of capillaries
increased no. mitochondria
kidneys conserve acid (decreased arterial pH)
66
Q

H+ drive is mediated through which chemoreceptors?

A

Peripheral

67
Q

How readily does H+ cross the blood brain barrier?

A

not much

68
Q

how do peripheral chemoreceptors adjust acidosis in the blood?

A

causes hyperventilation to increase elimination of CO2

69
Q

what stimulated peripheral chemoreceptors?

A

increased H+ in blood

70
Q

what are the major inspiratory muscles?

A

Diaphragm

External intercostal muscles

71
Q

what are the accessory muscles of inspiration?

A

Sternocleidomastoid
Scalenus
Pectoral

72
Q

What are the muscles of active expiration?

A

Abdominal muscles

internal intercostal muscles

73
Q

What is tidal volume (TV) and the average value?

A

Volume of air entering/leaving the lungs during a single breath
0.5 L

74
Q

what is inspiratory reserve volume (IRV) and the average value?

A

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

75
Q

what is expiratory reserve volume (ERV)?

A

extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
1.0 L

76
Q

what is residual volume (RV)?

A

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

77
Q

what is inspiratory capacity (IC)?

A

maximum volume of air that can be inspired at the end of a normal quiet expiration
IC= ERV + TV
3.5 L

78
Q

what is functional residual capacity (FRC)

A

Volume of air in the lungs at end of normal passive expiration
FRC = ERV + RV
2.2 L

79
Q

what is vital capacity (VC)

A

maximum volume of air that can be moved out during a single breath following a maximal inspiration
VC = IRV + TV + ERV
4.5 L

80
Q

what is total lung capacity? (TLC)

A

total volume of air the lungs can hold
TLC = VC + RV
5.7 L

81
Q

which volume cannot be measured by spirometry?

A

Residual volume

82
Q

What causes residual volume to increase?

A

When the elastic recoil of the lungs is lost (eg. emphysema)

83
Q

what can be determined from volume time curve?

A

FVC
FEV1
FEV1/FVC ratio

84
Q

what are dynamic lung volumes useful for?

A

Obstructive and restrictive lung disease

85
Q

what is FVC?

A

forced vital capacity- maximum volume that can be forcibly expelled from the lungs after a maximum inspiration

86
Q

what is FEV1?

A

Force expiratory volume in one second- volume of air that can be expired during the first second

87
Q

what is FEV1/FVC?

A

proportion of FVC that can be expired in first second

Normally >70%

88
Q

what would the spirometry results of a patient with an airway obstruction be?

A

Low/normal FVC
Low FEV1
Low FEV1/FVC%

89
Q

what would the spirometry results of a patient with a lung restriction be?

A

Low FVC
Low FEV1
Normal FEV1/FVC%

90
Q

What would the spirometry result of a patient with both obstruction and restriction?

A

Low FVC
Low FEV1
Low FEV1/FVC%

91
Q

What is the primary determinant of airway resistance?

A

Radius of conducting airway

92
Q

bronchoconstriction is caused by which type of stimulation?

A

Parasympathetic

93
Q

bronchodilation is caused by which type of stimulation?

A

Sympathetic

94
Q

expiration is more difficult than inspiration with patients with COPD or asthma due to?

A

Airway resistance

95
Q

what is dynamic airway compression?

A

pressure applied to alveolus pushes air out of the lungs

pressure applied to the airway is not desirable

96
Q

What happens with dynamic airway compression in patients with airway obstruction?

A

driving pressure is lost over obstructed segment
Causes fall in airway pressure along airway downstream
results in airway compression by rising pleural pressure during active expiration

97
Q

when is a peak flow test useful?

A

with patients with obstructive lung disease

98
Q

What is pulmonary compliance?

A

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

99
Q

what decreases pulmonary compliance?

A 
pulmonary fibrosis
pulmonary oedema
lung collapse
pneumonia
absence of surfactant
100
Q

what are the effects of decreased pulmonary compliance?

A

Lungs are stiffer
causes shortness of breath on exertion
Can cause a restrictive pattern of lung volumes in spirometry

101
Q

what increases pulmonary compliance?

A

If elastic recoil of lungs is lost
emphysema (hyperinfation of the lungs)
Age

102
Q

work of breathing is increased in which situations?

A

Decreased pulmonary compliance
Increased airway resistance
Decreased elastic recoil
When there’s a need for increased ventilation

103
Q

How would you calculate pulmonary ventilation?

A

the tidal volume x respiratory rate

104
Q

How would you calculate alveolar ventilation?

A

(tidal volume - dead space volume) x respiratory rate

105
Q

what is pulmonary ventilation?

A

the volume of air breathed in and out per minute

106
Q

what is alveolar ventilation?

A

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

107
Q

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

A

Dead space

108
Q

what is ventilation?

A

the rate at which gas is passing through the lungs

109
Q

what is perfusion?

A

the rate at which blood is passing through the lungs

110
Q

what is considered as alveolar dead space?

A

Ventilated alveoli which are not adequately perfused with blood

111
Q

what is physiological dead space?

A

anatomical dead space + alveolar dead space

112
Q

what does accumulation of CO2 in the alveoli as a result of increased perfusion do?

A

decrease airway resistance leading to increased airflow

113
Q

What is the partial pressure of O2 in the atmosphere?

A

~21 kPa

114
Q

what is the partial pressure of O2 in alveolar air?

not much difference between this, pulmonary capillaries and arterial blood

A

~13.3 kPa

115
Q

what is Henry’s law?

A

Gas dissolved in a liquid (blood) at constant temp. is proportional to the partial pressure of gas in equilibrium with the liquid.

116
Q

How much O2 is taken to the tissues as dissolved O2 under resting conditions?

A

15 ml/min

117
Q

How much O2 is taken to the tissues as dissolved O2 under strenuous exercise?

A

90ml/min

118
Q

What is the resting O2 consumption of our body cells?

A

250 ml/min

119
Q

How much of of O2 is carried by haemoglobin?

A

98.5%

120
Q

How many haem groups does haemoglobin have?

A

4

121
Q

How many oxygen molecules does each haem group reversibly bind to?

A

1

122
Q

How is haemoglobin described when all the Hb is carrying its maximum O2 load?

A

Fully saturated

123
Q

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

A

PO2

124
Q

What shape is the oxygen haemoglobin dissociation curve?

A

sigmoidal

125
Q

Whats the average resting PO2 at systemic capillaries?

A

5.3 kPa

126
Q

What is DO2I?

A

oxygen delivery index

127
Q

How do you calculate DO2I?

A

CaO2 x CI (oxygen content of arterial blood x Cardiac Index)

128
Q

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

A

1.34 x [Hb] x SaO2

129
Q

What can impair O2 delivery to the tissues?

A

Resp. disease- decreases arterial PO2, deccreases Hb saturation
Heart failure- decreases cardiac output
Anaemia- Decreases Hb concentration

130
Q

What happens to atmospheric pressure as altitude increases?

A

Atmospheric pressure decreases

131
Q

How to calculate the Partial pressure of O2 in alveolar air (PAO2)?

A

PiO2 - [PaCO2/0.8]

132
Q

What is the significance of the sigmoid correlation for haemolglobin?

A

Flat upper portions- moderate fall in alveolar PO2 will not affect O2 loading

Steep lower part- peripheral tissues get lots of O2 for small drop in capilliary PO2

133
Q

The bohr effect shows what on the sigmoid graph?

A

shift to the right

134
Q

What are the results of the bohr effecr?

A 
increased release of O2 by tissues
increased PCO2
increased [H+]
increased temp
increased 2,3- Biphosphoglycerate
135
Q

What shape is the myoglobin dissociation curve?

A

Hyperbolic

136
Q

What does presence of myoglobin in the blood indicate?

A

muscle damage

137
Q

What is the function of myoglobin?

A

Provides short term storage for O2 in the muscles for anaerobic conditions

138
Q

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

A

Solution 10%
Bicarbonate 60%
Carbamino compounds 30%

139
Q

how more soluable is carbon dioxide to oxygen?

A

20 times

140
Q

what enzyme catalyses the formation of bicarbonate from water and CO2?

A

Carbonic anhydrase

141
Q

what is the chloride shift?

A

when chloride enters the RBC and HCO3- leaves

142
Q

what are carbamino compounds formed from?

A

CO2 and terminal amine groups in blood proteins (globin)

143
Q

which can bind more CO2, HbO2 or Reduced Hb?

A

Reduced Hb

144
Q

What is the haldane effect?

A

Remoing O2 from Hb increases Hb’s affinity to pick up Co2 and Co2 generated H+

145
Q

what is the haldane effect on the CO2 dissociation curve?

A

Oxygen shifts the curve to the right

Respiratory (19 decks)

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