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MB1: Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

What is intracellular respiration

A

energy production within the cell - glycolysis, TCA, oxidative phosphorylation

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2
Q

What is external respiration

A

exchange of oxygen and carbon dioxide between cells and the environment
4 step process

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3
Q

4 Steps of external respiration

A

Ventilation
Gas exchange of O2 and CO2 from blood to alveoli
Gas transport in blood
Exchange of O2 and CO2 from blood to tissue

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4
Q

Define ventilation

A

mechanical gas exchange between atmosphere and alveoli

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5
Q

What is boyle’s law

A

At constant temperature the pressure of a gas varies to inverse of volume

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6
Q

True/false - ventilation can only occur when intra-alveolar pressure is greater than atmospheric pressure

A

False - ventilation occurs from high to low pressure so intra-alveolar pressure must be less than atmospheric

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7
Q

How are the lungs linked to the thorax?

A

Intrapleural fluid cohesiveness

Negative intrapleural pressure

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8
Q

Describe intrapleural fluid cohesiveness

A

water molecules in the intrapleural space stick and resist being pulled apart, sticking the membrane together

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9
Q

Describe negative intrapleural pressure

A

negative pressure creates a transmural pressure gradient across lung and chest wall
This negative pressure forces chest in towards lungs and lings out towards chest

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10
Q

True/ false - resting intra-alveolar pressure and atmospheric pressure are the same

A

True - they are both equal to roughly 760 mmHg or 101 kPa

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11
Q

What does intra-alveolar pressure drop to during inspiration

A

759 mmHg

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12
Q

What is the intrapleural pressure

A

754-756 mmHg

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13
Q

Describe inspiration

A

Diaphragm contracts to flatten, increasing thoracic volume vertically
External intercostals contract to lift ribs and move sternum up
Lung volume increases and so pressure drops causing air to be taken in

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14
Q

Describe expiration

A

Inspirarory muscles relax and lungs recoil by elasticity
Recoil causes volume decrease and so increases intra-alveolar pressure
Pressure gradient shifts and air is forced out of lungs

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15
Q

What is a pneumothorax and what does it do?

A

Air in pleural cavity

This can abolish transmural pressure gradient and can cause lung collapse

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16
Q

What is the transmural pressure gradient

A

difference in pressure between intra-alveolar and interpleural pressure

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17
Q

What are the causes of pneumothorax

A

Traumatic
Spontaneous
Iatrogenic

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18
Q

Physical signs and symptoms of a pneumothorax

A

Chest pain and shortness of breath

Hyperresonant percussion and decreased or absent breath sounds

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19
Q

How does the lung recoil

A

Elastic connective tissue

Alveolar surface tension

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20
Q

What is alveolar surface tension

A

Attraction of water molecules at liquid air surface

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21
Q

How is alveolar surface tension regulated

A

Presence of surfactant - mixture of lipids and proteins secreted by type II alveoli

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22
Q

What occurs in the absence of surfactant

A

surface tension would be too great and alveoli would collapse

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23
Q

What does surfactant do

A

intersperses water molecules and so lowers surface tension

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24
Q

What is LaPlace’s law?

A

Smaller alveoli with a smaller radius have a greater tendancy to collapse

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25
Q

What is alveolar interdependance

A

The stretch and recoil of surrounding alveoli to re-inflate a collapsed alveolus

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26
Q

What is respiratory distress syndrome of newborn

A

Premature babies cannpt produce enough surfactant as it is not made until late pregnancy
High alveolar surface tension and so very strenuous inspiration

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27
Q

What is the transmural pressure gradient opposed by?

A

elasticity of lung connective tissue

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28
Q

What is pulmonary surfactant and alveolar interdependence opposed by?

A

Alveolar surface tension

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29
Q

Name the major inspiratory muscles

A

Diaphragm

External intercostal muscles

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30
Q

Name the accessory inspiratory muscles

A

Scalenus
Pectoral
Sternocleidomastoid

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31
Q

Name the muscles of active expiration

A

Abdominal muscles

Internal intercostal muscles

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32
Q

What is tidal volume and its average value

A

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

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33
Q

What is inspiratory reserve volume and its average value

A

Extra volume of air that can be maximally inspired over and above resting tidal volume
3.0L

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34
Q

What is expiratory reserve volume and its average value

A

Extra air that can be actively expired by maximal contraction beyond normal value on tidal value
1.0L

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35
Q

What is residual volume and its average value

A

Minimum volume of air remaining in lungs following maximal expiration
1.2L

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36
Q

What is inspiratory capacity and its average value

A

Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC =IRV + TV)
3.5L

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37
Q

What is functional residual capacity and its average value

A

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

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38
Q

What is vital capacity and its average value

A

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

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39
Q

What is total lung capacity and its average value

A

Total volume of air the lungs can hold
(TLC = VC + RV)
5.7L

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40
Q

What are dynamic lung volumes useful for

A

diagnosis of obstructive and restrictive respiratory disease

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41
Q

What is FVC

A

forced vital capacity

Maximum volume of air that can be forcibly expelled from lungs following maximal inspiration

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42
Q

What is FEV1

A

Forced expiratory volume in one second

Volume of air expired in one second in an FVC determination

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43
Q

What is the FEV1/FVC ratio and what does it mean?

A

Proportion of FVC expired in the first second
it is (FEV1/FVC)x100
usually over 70%

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44
Q

What does the FEV1/FVC ratio and FVC value look like for someone with obstructive airway disease?

A

FVC will be low/normal

FEV1/FVC ratio will be low

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45
Q

What does the FEV1/FVC ratio and FVC value look like for someone with restrictive airway disease

A

FVC will be low

FEV1/FVC ratio will be normal

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46
Q

what is the determinant of airway resistance

A

The radius of the airway

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47
Q

what happens to Intrapleural pressure and airways during inspiration

A

intrapleural pressure decreases as thorax expands

Airways pulled open

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48
Q

What happens to intrapleural pressure and airways during expiration

A

Intrapleural pressure increases as thorax compresses

Airways close

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49
Q

what nerve branch stimulates bronchoconstriction

A

parasympathetic

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50
Q

What nerve branch stimulates bronchodilation

A

sympathetic

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51
Q

what makes expiration more difficult in patients with an airway obstruction

A

dynamic airway compression

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52
Q

What is dynamic airway compression

A

a rising pleural pressure which compresses airways and alveoli
It forces air out of alveoli, but restricts airway in the process

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53
Q

How do normal peoples airways not get affected by dynamic airway compression

A

the air resistance generated by the dynamic airway compression increases upstream pressure which opens the airways and increases the driving pressure downstream

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54
Q

How is a diseased persons airway more affected by dynamic airway compression

A

The driving force pressure is lost over the obstruction and so the airway is not kept open as well. Diseased airways are also more likely to collapse

55
Q

How is peak flow rate measured

A

Peak flow meter is used and patient blows sharply into it. the best of 3 attempts is used and charted for comparison to normal values
It is useful is diagnosing obstructive lung diseases

56
Q

What is pulmonary compliance

A

measure of effort used that goes into stretching or distending lungs

57
Q

Decreased compliance means

A

more work required to inflate lungs.
demonstrates restrictive pattern on spirometry
caused by pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia and surfactant absence

58
Q

Increased pulmonary compliance means

A

less effort required to inflate lungs but more difficut to deflate
occurs in emphysema (loss of elasticity)

59
Q

How much every is required for quiet breathing and what capacity do lungs operate at

A

3%

Half full

60
Q

What factors increase breathing work

A

Increased air resistance
Decreased compliance
decreased elastic recoil
need for increased ventilation

61
Q

What is anatomical dead space

A

Areas within the airways where inspired air remains but is unavailable for gas exchange

62
Q

Ventilation equation

A

Pulmonary ventilation = tidal volume x Resp rate

63
Q

Alveolar ventilation equation

A

Alveolar ventilation = (tidal volume - dead space volume) x resp rate

64
Q

Why is alveolar ventilation less than pulmonary ventilation

A

presence of anatomical dead space

65
Q

What is alveolar ventilation

A

volume of air exchanged between atmosphere and alveoli per minute

66
Q

how is pulmonary ventilation increased

A

Increase in tidal volume and resp rate

67
Q

How can alveolar ventilation be best increased

A

Slow, deep breathing. it is more advantageous to increase breathing depth due to anatomical dead space

68
Q

What is alveolar dead space and where is it most found

A

ventilated alveoli that are not adequately perfused with blood
This is minimal in healthy people and most seen with those with disease

69
Q

What is physiological dead space

A

the sum of anatomical dead space and alveolar dead space

70
Q

What is perfusion

A

rate at which blood is passing through lungs

71
Q

What is ventilation perfusion matching

A

alignment of ventilation and perfusion to maintain close arterial and alveolar partial oxygen pressures so best pressure of oxygen delivered to tissues
It is often close but not exact

72
Q

Local controls of ventilation perfusion matching act on what?

A

Smooth muscles of arterioles and airways

73
Q

An accumulation of carbon dioxide does what to assist ventilation perfusion matching

A

Decreases airway resistance

Blood vessels constrict in decrease of oxygen concentration

74
Q

An increase in alveolar oxygen concentration does what to increase ventilation perfusion matching

A

Increases vasodilation

decreased carbon dioxide levels cause constriction of local airways

75
Q

What are the factors affecting rate of gas exchange across the alveolar membane

A

Partial pressure gradient ox oxygen and carbon dioxide
Diffusion coefficient of oxygen and carbon dioxide
Surface area of alveolar membrane
Thickness of alveolar membrane

76
Q

What is daltons law of partial pressures

A

Pressure exerted by a gaseous mixture is the sum of all components of the mixture
Ptotal = P1+P2+Pn

77
Q

What is the partial pressure of a gas

A

pressure the gas would exert if it occupied the total volume of space but in the absence of other components

78
Q

True/false - partial pressure determines pressure gradient

A

True

79
Q

What is the alveolar gas equation

A

PAO2 = PiO2 - [PaCO2/0.8]

80
Q

What does the pressure of water saturated air in the resoiratry tract make up

A

47 mmHg

81
Q

there is a large difference in the partial pressure of oxygen between alveoli and arterioles. is this normal?

A

No. only small changes are normal

LArge changes signify gas exchange issues or a right to left shunt in heart

82
Q

What is the diffusion coefficient

A

a value which when is greater means a gas is more soluble in the membrane than other
Eg/ CO2 is more soluble than oxygen so has a greater diffusion coefficient

83
Q

What is fick’s law of diffusion

A

the amount of gas that moves across a tissue sheet in unit time is proportional to the area of the sheet but inversely proportional to thickness

84
Q

Lungs have a _____ surface area and a _____membrane to facilitate gas exchange

A

Large surface area

Thin membrane

85
Q

What are alveolar walls made up of

A

Type I alveolar cells

86
Q

What are the non respiratory functions of the respiratory system

A 
Vocalisation 
Water loss
Heat elimination 
Acid base balance 
Enhancement of venous return 
Removal of foreign bodies
87
Q

What is henry’s law?

A

amount of gas dissolved in a liquid is proportional to partial presure of gas in equilibrium with liquid

88
Q

true/false - blood on its own can supply the body with oxygen

A

False - it requires haemoglobin to bind to oxygen within the blood to supply tissues with oxygen

89
Q

What is the primary factor which determines the percentage saturation of haemoglobin

A

Partial pressure of oxygen (PO2)

90
Q

What shape curve is produced in the oxygen haemoglobin dissociation curve and what is the trend

A

Sigmoidal

Increased PO2 shows increased oxygen saturation

91
Q

What can oxygen delivery be impaired by?

A

Respiratory disease
Heart failure
Anaemia

92
Q

How does respiratory disease decrease oxygen saturations

A

Reduces PO2 and so saturates less haemoglobin

Less oxygen in blood

93
Q

How does anaemia reduce oxygen saturations

A

Decreases concentration of Hb so decreases concentration of oxygen in blood

94
Q

The binding of one oxygen molecule to haemoglobin increases ____ for Hb for oxygen

A

affinity

95
Q

what produces the sigmoidal curve on the oxygen haemoglobin dissociation curve

A

Cooperativity

96
Q

What would a moderate fall in PO2 do to oxygen saturation?

A

not much, oxygen loading would not be affected

97
Q

What would a small drop in PO2 do in peripheral tissues?

A

PO2 is already lower in peripheral tissues and so a small drop would have a significant effect on the curve
It causes haemoglobin saturation to drop as oxygen is delivered to tissues

98
Q

What is the bohr effect and what causes it?

A

right shift of the Oxygen Hb dissociation curve caused by an increased temperature, increased partial pressure carbon dioxide and reduced pH.
Increased 2,3-biphosphoglycerate
Hb affinity for oxygen drops and so more oxygen is released to tissues - where the bohn effect occurs

99
Q

How does HbF maintain high oxygen saturation at low PO2?

A

HbF interacts less with 2,3-biphosphoglycerate so has a higher affinity for oxygen than HbA
Left shift on O2 Hb dissociation curve so oxygen can be transferred mother to foetus even with low PO2

100
Q

Where is myoglobin present

A

Skeletal and cardiac muscles

101
Q

True/ false - myoglobin has a sigmoidal dissocation curve with oxygen

A

False - it is hyperbolic as myoglobin only has one haem group and cannot show cooperativity

102
Q

When does myoglobin release oxygen

A

very low PO2

103
Q

Why would myoglobin be present in blood

A

Muscle damage

104
Q

How is carbon dioxide transported in the blood

A

10% in solution
60% in bicarbonate
30% as carbamino compounds

105
Q

true/false - carbon dioxide is more soluble in solution than oxygen

A

true

106
Q

how is bicarbonate formed in the body

A

carbon dioxide and water react to form carbonic acid which dissociates to form a H ion and bicarbonate

107
Q

What catalyses the production of bicarbonate

A

carbonic anhydrase

108
Q

how is a carbamino compound formed

A

combination of CO2 and terminal amine groups in blood proteins

109
Q

globin of haemoglobin reacts with CO2 to produce

A

carbamino-haemoglobin

110
Q

where is bicarbonate found

A

inside red blood cells

111
Q

what is the haldane effect

A

states that removal of oxygen from Hb increases Hbs ability to pick up CO2 and H

112
Q

how does the bohr effect remove oxygen from Hb

A

shifts oxygen dissociation curve right at tissue level

113
Q

how does the haldane effect liberate CO2

A

presence of oxygen shifts CO2 dissociation curve right so liberates CO2 from Hb to increase oxygen uptake

114
Q

true/false - the haldane effect liberates CO2 in the lungs

A

true

115
Q

how does bicarbonate turn back to CO2 to diffuse into alveolus

A

Engages reverse reaction from bicarbonate to carbonic acid to CO2 and water

116
Q

why is oxygen given up at tissue level

A

lesser PO2 in tissue than alveolus so right shift on oxygen dissociation curve

117
Q

what part of the brain controls breathing

A

pre-botzinger complex of medulla in the brainstem

118
Q

what does the pre botzinger stimulate in inspiration

A

dorsal respiratory neurons

119
Q

what does the pre botzinger stimulate in passive expiration

A

nothing. it is not involve in expiration as it is passive

120
Q

What group of neurons excites internal intercostals and abdominal muscles in active expiration

A

ventral respiratory neurons, activated by increased firing from dorsal respiratory neurons

121
Q

What is pneumotaxic centre

A

terminates inspiration, without it breathing would be prolonged (apneusis)

122
Q

what is the apneustic centre

A

Excites inspiratory area of medulla

Prolongs inspiration

123
Q

What external stimuli influence breathing

A 
Higher brain centres
Stretch receptors
Juxtapulmonary receptors 
Baroreceptors 
Central and peripheral chemoreceptors
124
Q

What is the hering breuer reflex

A

stretch receptors that are activated by inspiration prevent overinflation

125
Q

How does exercise influence breathing

A

body movement reflex
release of adrenaline
accumulation of CO2 and H
increased temperature

126
Q

What is the cough reflex for, how is it conduced

A

removes dust, dirt or excess secretions

Short intake of air, closure of larynx, abdominal muscles contract and larynx opens to expel air

127
Q

Where are peripheral chemoreceptors located and what do they sense

A

carotid and aortic bodies

sense tension of oxygen, H and carbon dioxide in blood

128
Q

where are central chemoreceptors located and what do they sense

A

surface of medulla

respond to [H] in CSF

129
Q

when is the hypoxic drive of respiration stimulated

What can it be important in

A

when PO2 falls below 8 kPa

important in CO2 retention

130
Q

the partial pressure of oxygen decreases with _____

A

increased altitude

131
Q

what is the acute response to hypoxia

A

hyperventilation, increased cardiac output (tachycardia)

132
Q

how is high altitude hypoxia controlled chronically

A 
Polycythaemia
Increased 2,3-biphosphoglycerate
increased number of capillaries 
Increased number of mitochondria 
Decrease in arterial pH
133
Q

What chemoreceptors sense the H drive of respiration

A

Peripheral, H cannot cross the blood brain barrier

134
Q

what does stimulation by H cause

A

hyperventilation to increase elimination of CO2

MB1: Respiratory (15 decks)

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