Physiology Flashcards
1
Q
What is intracellular respiration
A
energy production within the cell - glycolysis, TCA, oxidative phosphorylation
2
Q
What is external respiration
A
exchange of oxygen and carbon dioxide between cells and the environment
4 step process
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
4
Q
Define ventilation
A
mechanical gas exchange between atmosphere and alveoli
5
Q
What is boyle’s law
A
At constant temperature the pressure of a gas varies to inverse of volume
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
7
Q
How are the lungs linked to the thorax?
A
Intrapleural fluid cohesiveness
Negative intrapleural pressure
8
Q
Describe intrapleural fluid cohesiveness
A
water molecules in the intrapleural space stick and resist being pulled apart, sticking the membrane together
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
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
11
Q
What does intra-alveolar pressure drop to during inspiration
A
759 mmHg
12
Q
What is the intrapleural pressure
A
754-756 mmHg
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
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
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
16
Q
What is the transmural pressure gradient
A
difference in pressure between intra-alveolar and interpleural pressure
17
Q
What are the causes of pneumothorax
A
Traumatic
Spontaneous
Iatrogenic
18
Q
Physical signs and symptoms of a pneumothorax
A
Chest pain and shortness of breath
Hyperresonant percussion and decreased or absent breath sounds
19
Q
How does the lung recoil
A
Elastic connective tissue
Alveolar surface tension
20
Q
What is alveolar surface tension
A
Attraction of water molecules at liquid air surface
21
Q
How is alveolar surface tension regulated
A
Presence of surfactant - mixture of lipids and proteins secreted by type II alveoli
22
Q
What occurs in the absence of surfactant
A
surface tension would be too great and alveoli would collapse
23
Q
What does surfactant do
A
intersperses water molecules and so lowers surface tension
24
Q
What is LaPlace’s law?
A
Smaller alveoli with a smaller radius have a greater tendancy to collapse
25
What is alveolar interdependance
The stretch and recoil of surrounding alveoli to re-inflate a collapsed alveolus
26
What is respiratory distress syndrome of newborn
Premature babies cannpt produce enough surfactant as it is not made until late pregnancy
High alveolar surface tension and so very strenuous inspiration
27
What is the transmural pressure gradient opposed by?
elasticity of lung connective tissue
28
What is pulmonary surfactant and alveolar interdependence opposed by?
Alveolar surface tension
29
Name the major inspiratory muscles
Diaphragm
| External intercostal muscles
30
Name the accessory inspiratory muscles
Scalenus
Pectoral
Sternocleidomastoid
31
Name the muscles of active expiration
Abdominal muscles
| Internal intercostal muscles
32
What is tidal volume and its average value
Volume of air entering or leaving lungs during a single breath
0.5L
33
What is inspiratory reserve volume and its average value
Extra volume of air that can be maximally inspired over and above resting tidal volume
3.0L
34
What is expiratory reserve volume and its average value
Extra air that can be actively expired by maximal contraction beyond normal value on tidal value
1.0L
35
What is residual volume and its average value
Minimum volume of air remaining in lungs following maximal expiration
1.2L
36
What is inspiratory capacity and its average value
Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC =IRV + TV)
3.5L
37
What is functional residual capacity and its average value
Volume of air in lungs at end of normal passive expiration (FRC = ERV + RV)
2.2L
38
What is vital capacity and its average value
Maximum volume of air that can be moved out during a single breath following a maximal inspiration (VC = IRV + TV + ERV)
4.5L
39
What is total lung capacity and its average value
Total volume of air the lungs can hold
(TLC = VC + RV)
5.7L
40
What are dynamic lung volumes useful for
diagnosis of obstructive and restrictive respiratory disease
41
What is FVC
forced vital capacity
| Maximum volume of air that can be forcibly expelled from lungs following maximal inspiration
42
What is FEV1
Forced expiratory volume in one second
| Volume of air expired in one second in an FVC determination
43
What is the FEV1/FVC ratio and what does it mean?
Proportion of FVC expired in the first second
it is (FEV1/FVC)x100
usually over 70%
44
What does the FEV1/FVC ratio and FVC value look like for someone with obstructive airway disease?
FVC will be low/normal
| FEV1/FVC ratio will be low
45
What does the FEV1/FVC ratio and FVC value look like for someone with restrictive airway disease
FVC will be low
| FEV1/FVC ratio will be normal
46
what is the determinant of airway resistance
The radius of the airway
47
what happens to Intrapleural pressure and airways during inspiration
intrapleural pressure decreases as thorax expands
| Airways pulled open
48
What happens to intrapleural pressure and airways during expiration
Intrapleural pressure increases as thorax compresses
| Airways close
49
what nerve branch stimulates bronchoconstriction
parasympathetic
50
What nerve branch stimulates bronchodilation
sympathetic
51
what makes expiration more difficult in patients with an airway obstruction
dynamic airway compression
52
What is dynamic airway compression
a rising pleural pressure which compresses airways and alveoli
It forces air out of alveoli, but restricts airway in the process
53
How do normal peoples airways not get affected by dynamic airway compression
the air resistance generated by the dynamic airway compression increases upstream pressure which opens the airways and increases the driving pressure downstream
54
How is a diseased persons airway more affected by dynamic airway compression
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
How is peak flow rate measured
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
What is pulmonary compliance
measure of effort used that goes into stretching or distending lungs
57
Decreased compliance means
more work required to inflate lungs.
demonstrates restrictive pattern on spirometry
caused by pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia and surfactant absence
58
Increased pulmonary compliance means
less effort required to inflate lungs but more difficut to deflate
occurs in emphysema (loss of elasticity)
59
How much every is required for quiet breathing and what capacity do lungs operate at
3%
| Half full
60
What factors increase breathing work
Increased air resistance
Decreased compliance
decreased elastic recoil
need for increased ventilation
61
What is anatomical dead space
Areas within the airways where inspired air remains but is unavailable for gas exchange
62
Ventilation equation
Pulmonary ventilation = tidal volume x Resp rate
63
Alveolar ventilation equation
Alveolar ventilation = (tidal volume - dead space volume) x resp rate
64
Why is alveolar ventilation less than pulmonary ventilation
presence of anatomical dead space
65
What is alveolar ventilation
volume of air exchanged between atmosphere and alveoli per minute
66
how is pulmonary ventilation increased
Increase in tidal volume and resp rate
67
How can alveolar ventilation be best increased
Slow, deep breathing. it is more advantageous to increase breathing depth due to anatomical dead space
68
What is alveolar dead space and where is it most found
ventilated alveoli that are not adequately perfused with blood
This is minimal in healthy people and most seen with those with disease
69
What is physiological dead space
the sum of anatomical dead space and alveolar dead space
70
What is perfusion
rate at which blood is passing through lungs
71
What is ventilation perfusion matching
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
Local controls of ventilation perfusion matching act on what?
Smooth muscles of arterioles and airways
73
An accumulation of carbon dioxide does what to assist ventilation perfusion matching
Decreases airway resistance
| Blood vessels constrict in decrease of oxygen concentration
74
An increase in alveolar oxygen concentration does what to increase ventilation perfusion matching
Increases vasodilation
| decreased carbon dioxide levels cause constriction of local airways
75
What are the factors affecting rate of gas exchange across the alveolar membane
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
What is daltons law of partial pressures
Pressure exerted by a gaseous mixture is the sum of all components of the mixture
Ptotal = P1+P2+Pn
77
What is the partial pressure of a gas
pressure the gas would exert if it occupied the total volume of space but in the absence of other components
78
True/false - partial pressure determines pressure gradient
True
79
What is the alveolar gas equation
PAO2 = PiO2 - [PaCO2/0.8]
80
What does the pressure of water saturated air in the resoiratry tract make up
47 mmHg
81
there is a large difference in the partial pressure of oxygen between alveoli and arterioles. is this normal?
No. only small changes are normal
| LArge changes signify gas exchange issues or a right to left shunt in heart
82
What is the diffusion coefficient
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
What is fick's law of diffusion
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
Lungs have a _____ surface area and a _____membrane to facilitate gas exchange
Large surface area
| Thin membrane
85
What are alveolar walls made up of
Type I alveolar cells
86
What are the non respiratory functions of the respiratory system
```
Vocalisation
Water loss
Heat elimination
Acid base balance
Enhancement of venous return
Removal of foreign bodies
```
87
What is henry's law?
amount of gas dissolved in a liquid is proportional to partial presure of gas in equilibrium with liquid
88
true/false - blood on its own can supply the body with oxygen
False - it requires haemoglobin to bind to oxygen within the blood to supply tissues with oxygen
89
What is the primary factor which determines the percentage saturation of haemoglobin
Partial pressure of oxygen (PO2)
90
What shape curve is produced in the oxygen haemoglobin dissociation curve and what is the trend
Sigmoidal
| Increased PO2 shows increased oxygen saturation
91
What can oxygen delivery be impaired by?
Respiratory disease
Heart failure
Anaemia
92
How does respiratory disease decrease oxygen saturations
Reduces PO2 and so saturates less haemoglobin
| Less oxygen in blood
93
How does anaemia reduce oxygen saturations
Decreases concentration of Hb so decreases concentration of oxygen in blood
94
The binding of one oxygen molecule to haemoglobin increases ____ for Hb for oxygen
affinity
95
what produces the sigmoidal curve on the oxygen haemoglobin dissociation curve
Cooperativity
96
What would a moderate fall in PO2 do to oxygen saturation?
not much, oxygen loading would not be affected
97
What would a small drop in PO2 do in peripheral tissues?
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
What is the bohr effect and what causes it?
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
How does HbF maintain high oxygen saturation at low PO2?
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
Where is myoglobin present
Skeletal and cardiac muscles
101
True/ false - myoglobin has a sigmoidal dissocation curve with oxygen
False - it is hyperbolic as myoglobin only has one haem group and cannot show cooperativity
102
When does myoglobin release oxygen
very low PO2
103
Why would myoglobin be present in blood
Muscle damage
104
How is carbon dioxide transported in the blood
10% in solution
60% in bicarbonate
30% as carbamino compounds
105
true/false - carbon dioxide is more soluble in solution than oxygen
true
106
how is bicarbonate formed in the body
carbon dioxide and water react to form carbonic acid which dissociates to form a H ion and bicarbonate
107
What catalyses the production of bicarbonate
carbonic anhydrase
108
how is a carbamino compound formed
combination of CO2 and terminal amine groups in blood proteins
109
globin of haemoglobin reacts with CO2 to produce
carbamino-haemoglobin
110
where is bicarbonate found
inside red blood cells
111
what is the haldane effect
states that removal of oxygen from Hb increases Hbs ability to pick up CO2 and H
112
how does the bohr effect remove oxygen from Hb
shifts oxygen dissociation curve right at tissue level
113
how does the haldane effect liberate CO2
presence of oxygen shifts CO2 dissociation curve right so liberates CO2 from Hb to increase oxygen uptake
114
true/false - the haldane effect liberates CO2 in the lungs
true
115
how does bicarbonate turn back to CO2 to diffuse into alveolus
Engages reverse reaction from bicarbonate to carbonic acid to CO2 and water
116
why is oxygen given up at tissue level
lesser PO2 in tissue than alveolus so right shift on oxygen dissociation curve
117
what part of the brain controls breathing
pre-botzinger complex of medulla in the brainstem
118
what does the pre botzinger stimulate in inspiration
dorsal respiratory neurons
119
what does the pre botzinger stimulate in passive expiration
nothing. it is not involve in expiration as it is passive
120
What group of neurons excites internal intercostals and abdominal muscles in active expiration
ventral respiratory neurons, activated by increased firing from dorsal respiratory neurons
121
What is pneumotaxic centre
terminates inspiration, without it breathing would be prolonged (apneusis)
122
what is the apneustic centre
Excites inspiratory area of medulla
| Prolongs inspiration
123
What external stimuli influence breathing
```
Higher brain centres
Stretch receptors
Juxtapulmonary receptors
Baroreceptors
Central and peripheral chemoreceptors
```
124
What is the hering breuer reflex
stretch receptors that are activated by inspiration prevent overinflation
125
How does exercise influence breathing
body movement reflex
release of adrenaline
accumulation of CO2 and H
increased temperature
126
What is the cough reflex for, how is it conduced
removes dust, dirt or excess secretions
| Short intake of air, closure of larynx, abdominal muscles contract and larynx opens to expel air
127
Where are peripheral chemoreceptors located and what do they sense
carotid and aortic bodies
| sense tension of oxygen, H and carbon dioxide in blood
128
where are central chemoreceptors located and what do they sense
surface of medulla
| respond to [H] in CSF
129
when is the hypoxic drive of respiration stimulated
| What can it be important in
when PO2 falls below 8 kPa
| important in CO2 retention
130
the partial pressure of oxygen decreases with _____
increased altitude
131
what is the acute response to hypoxia
hyperventilation, increased cardiac output (tachycardia)
132
how is high altitude hypoxia controlled chronically
```
Polycythaemia
Increased 2,3-biphosphoglycerate
increased number of capillaries
Increased number of mitochondria
Decrease in arterial pH
```
133
What chemoreceptors sense the H drive of respiration
Peripheral, H cannot cross the blood brain barrier
134
what does stimulation by H cause
hyperventilation to increase elimination of CO2
