Respiration Flashcards
(156 cards)
1
Q
What is the flow of air into/out of the lungs proportional to?
A
Pressure gradient
2
Q
What is the flow of air into/out of the lungs inversely proportional to?
A
Resistance
3
Q
What is the main relationship demonstrated by Poiseuille’s law?
A
Airway resistance is inversely proportional to the fourth power of the radius
4
Q
What do small changes in airway diameter impact?
A
The resistance of airflow (small change in diameter = big change in resistance)
5
Q
What percentage of the total airway resistance is made up by the pharynx-larynx?
A
40%
6
Q
What percentage of the total airway resistance is made up by the large airways (>2mm diameter)?
A
40%
7
Q
What percentage of the total airway resistance is made up by the small airways (<2mm diameter)?
A
20%
8
Q
What factors impact airway diameter and therefore resistance? (3)
A
- Increased mucus secretion
- Oedema
- Airway collapse/expansion during normal breathing
9
Q
What are the 2 categories of lung disease?
A
- Obstructive
- Restrictive
10
Q
What is obstructive lung disease?
A
Narrowing of the airways causes a reduction in flow
11
Q
What is restrictive lung disease?
A
Causes a reduction in lung expansion
12
Q
What is the effect of both obstructive and restrictive lung disease?
A
Both reduce ventilation
13
Q
What is FEV1?
A
Forced expiratory volume in 1 second
14
Q
What is VC?
A
- Vital Capacity
- Maximum volume of air that can be expelled from the lungs after biggest possible deep breath
15
Q
What is the ratio of FEV1:VC in healthy lungs?
A
Greater than 80%
16
Q
Which graphs are used to diagnose lung diseases? (2)
A
- Volume/time
- Flow/volume
17
Q
What causes narrowing of the airways in obstructive lung disease? (3)
A
- Excess secretions
- Bronchoconstriction (airway smooth muscle contraction - asthma)
- Inflammation
18
Q
What is FVC?
A
- Forced Vital Capacity
- Volume of air exhaled with maximal effort after maximum inspiration
19
Q
Which measurement is affected in obstructive lung disease?
A
- FEV1 decreased
- FVC usually unaltered
20
Q
What is a sign of obstructive lung disease on a flow/volume graph?
A
Concave shaped decline in flow rate
21
Q
What are examples of obstructive lung disease? (4)
A
- Asthma
- COPD
- Chronic bronchitis
- Emphysema
22
Q
What does COPD stand for?
A
Chronic Obstructive Pulmonary Disease
23
Q
What happens in emphysema?
A
Loss of elastin
24
Q
Which diseases are classed as subtypes of COPD? (2)
A
- Chronic bronchitis
- Emphysema
25
What forces are interacting to keep the pressure of the intrapleural space less than atmospheric pressure?
- Elastic recoil of the lungs tends to make them collapse inwards
- Elastic recoil of the chest wall tends to make it expand
- Inward and outward forces balance
26
What are the 4 types of airflow?
- Laminar
- Unstable (switching between)
- Turbulent
- Transitional
27
What factors influence the Reynolds number? (4)
- Viscosity
- Density
- Radius of vessel
- Velocity
28
What state of airflow is the fluid in if the Reynolds number is <2000?
Laminar
29
What state of airflow is the fluid in if the Reynolds number is between 2000 and 3000?
Unstable
30
What state of airflow is the fluid in if the Reynolds number is >2000?
Turbulent
31
What is the pressure gradient in the lungs?
Difference in pressure between the alveoli and the atmospheric pressure
32
How do you calculate airflow in a laminar state?
- Airflow is proportional to the pressure gradient and inversely proportional to the resistance
- Airflow = difference in pressure over resistance
33
Where in the airway is the flow rate the fastest?
- Centre
- Slows as you move towards the edges
34
What kind of airflow occurs in most of the areas of the lungs?
Turbulent
35
How do you calculate airflow in a turbulent state?
Airflow is proportional to the square root of the pressure difference
36
Which type of airflow needs a greater pressure gradient to achieve the same flow rate?
Turbulent (proportional to square root of pressure gradient)
37
What is transitional flow?
- Jumping between laminar and turbulent type flow at the branching points of the airways
- Bifurcations disrupt flow
38
What is COPD characterised by? (2)
- Increase in airway resistance
- Decrease in airflow
39
What is Chronic Bronchitis?
Long term inflammation of the bronchi and bronchioles
40
What is Emphysema?
Destruction of alveoli walls
41
How is COPD treated? (2)
- Bronchodilators (anticholinergics or beta-2 adrenoreceptor agonists)
- Glucocorticosteroids
42
What is the total airway resistance in a healthy individual?
1.5cm H2O .s.litres^-1
43
What is the total airway resistance in an individual with COPD?
5.0cm H2O .s.litres^-1
44
Why does the total ariway resistance increase in COPD patients?
Massive increase in resistance in the small airways (<2mm)
45
What percentage of the total airway resistance is made up by the small airways (<2mm diameter) in COPD patients?
70%
46
What happens to the diameter of the airways during inspiration?
Increases - dilation
47
What happens to the diameter of the airways during expiration?
Decreases - collapse
48
What happens to the resistance of the airways during inspiration?
Decreases
49
What happens to the resistance of the airways during expiration?
Increases
50
What is the pressure in the intrapleural space?
Sub-atmospheric
51
What keeps the lungs from collapsing?
The sub-atmospheric pressure in the intrapleural space
52
What happens in Emphysema?
- Loss of elastic tissue and breakdown of alveolar walls
- Collapse of airways during expiration is exaggerated
53
What is the resting lung volume like in an Emphysema patient compared to a healthy individual?
Higher than a healthy person
54
What is tidal volume?
Volume of air you breathe in with one breath
55
What effect does COPD have on the rate of inflation?
Decreases due to increased resistance in the airways
56
What are the 2 zones of the lungs?
- Conducting zone
- Respiratory zone
57
What is the respiratory zone?
- Alveoli
- Where gas exchange occurs
58
What is the conducting zone?
- All the airways which get the air to the alveoli (respiratory zone)
- Trachea to bronchioles
59
What are the 2 types of dead space?
- Anatomical dead space
- Physiological dead space
60
What is anatomical dead space? (2)
- Volume of the conducting conducting airways
- 30% of inspired air
61
What is physiological dead space? (2)
- Volume of lungs not participating in gas exchange
- Made up of the conducting zone and the non-functional areas of the respiratory zone
62
How do physiological and anatomical dead space differ in healthy individuals?
Values should be the same
63
What is compliance? (2)
- Measure of elasticity/distensibility
- The ease with which the lungs/thorax expand during pressure changes
64
How is compliance effected by emphysema?
- High compliance
- Airways collapse more easily during expiration
65
How is compliance effected by fibrosis?
- Low compliance
- More rigid
66
What is total ventilation?
Volume of air moved out of the lungs per unit time
67
What is the normal tidal volume at rest?
0.5 litres
68
What is normal breathing frequency?
12 breaths a minute
69
What is alveolar ventilation?
Volume of 'fresh' air reaching the respiratory zone
70
How do you calculate alveolar ventilation?
Total ventilation - dead space ventilation
71
What volume of air is in the dead space?
0.15 litres
72
What happens to alveolar and arterial gas composition during hyperventilation?
- Same amount of CO2 is being expelled in a larger volume of air so the partial pressure of CO2 in the alveolar gas decreases
- The partial pressure of CO2 in the arterial blood also decreases to reach equilibrium
- Results in respiratory alkalosis
73
What happens to alveolar and arterial gas composition during hypoventilation?
- Same amount of CO2 is being expelled in a smaller volume of air so the partial pressure of CO2 in the alveolar gas increases
- The partial pressure of CO2 in the arterial blood also increases to reach equilibrium
- Results in respiratory acidosis
74
What causes respiratory acidosis?
Hypoventilation
75
What causes respiratory alkalosis?
Hyperventilation
76
Where in the lungs has the lowest ventilation?
Apex
77
Where in the lungs has the highest ventilation?
Base
78
Why is ventilation low at the apex of the lungs?
- Lung weight pulling down causes a more negative intrapleural pressure so alveoli have a greater starting volume
- This means they have a lower compliance because they can't expand that much
79
Why is ventilation high at the base of the lungs?
- Less negative intrapleural pressure so the alveoli have a smaller starting volume
- Alveoli have a greater capacity to expand so have a higher compliance
80
What are the 2 circulation systems?
- Pulmonary
- Systemic
81
Is systemic circulation high or low pressure?
High pressure, high resistance
82
Is pulmonary circulation high or low pressure?
Low pressure, low resistance
83
When is pulmonary resistance at its lowest?
When the lungs are at functional residual capacity
84
What is functional residual capacity?
Volume of air left in the lungs after a normal exhalation
85
What are the 2 types of blood vessels in the lungs?
- Alveolar vessels
- Extra-alveolar vessels
86
What are alveolar vessels?
Capillaries/small blood vessels which are surrounded by alveoli
87
What are extra-alveolar vessels?
Blood vessels not surrounded by alveoli
88
How does an increase in intrapleural pressure affect the extra-alveolar vessels?
- More negative intrapleural pressure (bigger vacuum) causes extra-alveolar vessels to expand
- Resistance goes down
89
How does a decrease in intrapleural pressure affect the extra-alveolar vessels?
- Less negative intrapleural pressure (smaller vacuum) causes the diameter of extra-alveolar vessels to decrease
- Resistance increases
90
How do you calculate the total pulmonary resistance?
Sum of alveolar and extra-alveolar vessel resistances
91
What is residual volume?
Volume of air remaining in the lungs after a maximum forceful expiration
92
When is intrapleural pressure most negative?
During inspiration
93
What happens to alveolar vessel resistance during inspiration?
- Alveoli expand which puts pressure on the alveolar vessels so they can't expand as much
- Resistance increases
94
What happens to extra-alveolar vessel resistance during inspiration?
- Intrapleural pressure becomes more negative which causes extra-alveolar vessels to expand
- Resistance decreases
95
What is capillary recruitment?
- At rest some capillaries are conducting blood, some are open and NOT conducting blood and some are collapsed
- As perfusion pressure increases (e.g. during exercise), previously non-conducting vessels start conducting blood and the collapsed vessels open
- Further pressure increase causes all vessels to conduct blood which lowers system resistance
96
Where in the lungs has the lowest perfusion?
Apex
97
Where in the lungs has the highest perfusion?
Base
98
Why is perfusion lower at the top of the lungs?
Blood is being pumped against gravity
99
What are the zones of the lungs?
- Zone 1 to 4
- Only zone 2-4 in healthy lungs
100
What effect does a decrease in oxygen have on perfusion?
Causes vasoconstriction because the lungs sense a problem and direct the blood elsewhere
101
What effect does an increase in oxygen have on perfusion?
Causes vasodilation
102
What effect does a decrease in carbon dioxide have on perfusion?
Causes vasodilation
103
What effect does an increase in carbon dioxide have on perfusion?
Causes vasoconstriction
104
What is the ventilation-perfusion ratio?
Ratio = V/Q
105
What happens to the ventilation-perfusion ratio when there is no ventilation?
Ratio is 0
106
What happens to the ventilation-perfusion ratio when there is no perfusion?
Ratio is infinity
107
Where in the lungs is the ventilation-perfusion ratio the highest?
Apex
108
Where in the lungs is the ventilation-perfusion ratio the lowest?
Base
109
What happens to the ventilation-perfusion ratio during pulmonary embolism? (4)
- Perfusion reduced
- Alveolar gas composition becomes the same as inspired air due to no gas exchange
- Ratio becomes infinity
- Blood directed elsewhere
110
What happens to the ventilation-perfusion ratio when something blocks airflow in the lungs? (4)
- Ventilation reduced
- Alveolar gas composition becomes the same as venous blood
- Ratio becomes 0
- Air and blood directed elsewhere
111
What is the effect of stimulating a Gq protein coupled receptor? (4)
- Alpha subunit dissociates and activates phospholipase C (PLC)
- PLC cleaves PIP2 into diacylglycerol (DAG) and IP3
- DAG stimulates protein kinase C (PKC)
- IP3 causes release of Ca2+ from stores
112
Which molecule is Gq linked to?
Phospholipase C (PLC)
113
Which molecule is Gs linked to?
Adenylyl cyclase
114
Which molecule is Gi linked to?
Adenylyl cyclase
115
Which molecule is Gi linked to?
Adenylyl cyclase
116
What is the effect of stimulating a Gs protein coupled receptor?
- Alpha subunit dissociates and activates adenylyl cyclase
- Causes increase of cAMP and activation of protein kinase A
117
What is the effect of stimulating a Gi protein coupled receptor?
- Alpha subunit dissociates and inhibits adenylyl cyclase
- Causes a reduction in cAMP and reduction of protein kinase A activity
118
What are the divisions of the autonomic nervous system? (3)
- Sympathetic
- Parasympathetic
- Enteric
119
What effect does the parasympathetic nervous system have on bronchial smooth muscle?
Vagus nerve releases acetylcholine which acts on muscarinic receptors, causing constriction
120
What effect does the sympathetic nervous system have on bronchial smooth muscle?
Nerves release noradrenaline which acts on adrenergic receptors, causing dilation
121
What humoral factors can affect bronchial smooth muscle?
- Adrenaline
- Histamine
122
What effect does adrenaline have on bronchial smooth muscle?
Dilation
123
What effect does histamine have on bronchial smooth muscle?
Constriction
124
What is a short acting asthma treatment?
Salbutamol
125
How does salbutamol work?
- Short-acting beta-2 adrenoreceptor agonist
- Causes airway dilation
126
What is a long-term asthma treatment? (2)
- Glucocorticoids e.g. beclomethasone
- Long acting beta adrenoreceptor agonists
127
How does beclomethasone work?
- Inhaled steroids
- Reduce inflammation
128
What is the mechanism of smooth muscle contraction? (6)
- Increase in intracellular Ca2+
- Ca2+ binds to calmodulin creating active Ca2+-calmodulin complex
- Complex activates Myosin Light Chain Kinase (MLCK)
- MLCK phosphorylates myosin light chain
- Causes contraction
- Contraction is maintained while the myosin light chain remains phosphorylated
129
What is the mechanism of smooth muscle relaxation? (2)
- Myosin Light Chain Phosphatase (MLCP) dephosphorylates the myosin light chain
- Causes relaxation
130
Which receptors present on smooth muscle are Gq coupled? (3)
- M3 muscarinic receptors
- H1 histamine receptors
- BK bradykinin receptors
131
What is the effect of stimulating Gq receptors on smooth muscle? (2)
- IP3 causes Ca2+ release and therefore muscle CONTRACTION
- DAG activates PKC which causes growth in the long term
132
Which receptors present on smooth muscle are Gs coupled? (2)
- Beta-2 adrenergic receptors
- VIP (Vasoactive Intestinal Peptide) receptors
133
What is the effect of stimulating Gs receptors on smooth muscle? (6)
- RELAXATION
- Protein Kinase A activated
- Causes stimulation of BK K+ channels so K+ leaves and hyperpolarises the membrane
- Inhibits MLCK and activates MLCP
- Gene regulation
- Inhibits growth
134
What is the effect of stimulating Gi receptors on smooth muscle? (3)
- Counteracts the action of Gs
- Opposes the relaxation of smooth muscle
- Inhibits the BK K+ channel
135
Which receptors present on smooth muscle are Gi coupled?
M2 muscarinic receptors
136
Which receptors cause smooth muscle contraction?
M3 receptors
137
What is the negative feedback mechanism which prevents over-contraction of airway smooth muscle?
- ACh released from postganglionic nerve fibre and activates M3 receptors on smooth muscle causing contraction
- Some of the ACh activates M2 receptors on the postganglionic nerve fibre which inhibits further ACh release
138
What kind of receptors are adrenergic receptors?
G protein coupled
139
Which G protein are beta-2 adrenergic receptors coupled to?
Gs
140
What is NANC signalling?
Nonadrenergic/noncholinergic signalling
141
What are the 2 pathways of NANC signalling?
- eNANC (excitatory)
- iNANC (inhibitory)
142
What happens in eNANC?
Causes bronchoconstriction
143
Which transmitters are involved in eNANC? (2)
- Substance P
- Neurokinin A
144
Which transmitters are involved in iNANC? (3)
- Vasoactive Intestinal Peptide (VIP)
- Nitric Oxide
- Neuropeptide Y
145
What happens in iNANC?
Causes bronchodilation
146
What are the 2 classes of asthma?
- Atopic (extrinsic)
- Non-atopic (intrinsic)
147
What is the effect of histamine on airway smooth muscle?
Bronchoconstriction
148
What are the characteristics of atopic asthma? (4)
- Associated with allergies
- Linked to elevated serum IgE and positive skin-prick test
- Allergen causes activation of mast cells which release histamine (bronchoconstriction)
- Other inflammatory cells activated e.g. eosinophils
149
What are the characteristics of non-atopic asthma? (3)
- Normal serum IgE and no positive skin-prick test
- Induced by exercise, cold air, inhaled irritants, stress, drugs
- May have a localised increase in IgE
150
Which division of the nervous system is overactive in asthma?
Parasympathetic
151
What is the effect of increased parasympathetic activity in asthma? (5)
- Increased basal tone
- Increased muscle constriction in response to irritants
- ACh activates M3 receptors on goblet cells causing increased mucus secretion
- ACh activates M3 receptors on smooth muscle causing bronchoconstriction and long term growth of cells (thicker layer of muscle)
- Inflammatory cells activated
152
How are M2 receptors linked to asthma?
- Reduced neuronal M2 receptor activity leads to increased parasympathetic activity
- M2 receptors are involved in negative feedback which prevents over-activation of smooth muscle
153
How are eosinophils involved in asthma? (3)
- Eosinophils cluster around the nerve fibres
- Activated eosinophils release Major Basic Protein (MBP)
- MBP inhibit M2 receptors which inhibits negative feedback
154
How can anticholinergics be used to treat asthma? (2)
- Competitive inhibitors of M1, M2 and M3 receptors
- Block the effects of endogenous ACh
155
What is Ipratropium?
Short-lasting anticholinergic drug used in combination with short-acting beta-2 adrenoreceptor agonists e.g. salbutamol
156
What is Tiotropium?
Long-lasting anticholinergic drug used in combination with long-acting beta-2 adrenoreceptor agonists and inhaled corticosteroids
