Physiology Flashcards
1
Q
What are the two types of respiration?
A
Internal & External
2
Q
What is internal respiration?
A
the intracellular mechanisms which consume oxygen and produce carbon dioxide
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
4
Q
State the four steps of external respiration
A
- Ventilation
- Gas exchange
- Transport in the blood
- Exchange at tissue level
5
Q
Name four systems involved in external respiration
A
- Respiratory
- Cardiovascular
- Haematology
- Nervous
6
Q
What is ventilation?
A
The mechanical process of moving air between the atmosphere and the alveolar sacs
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
8
Q
Describe the pressure difference before inspiration
A
The intra-alveolar pressure is equivalent to the atmospheric pressure
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
10
Q
State two ways in which the lungs are linked to the thorax
A
- Intra-pleural fluid cohesiveness
2. Negative intra-pleural pressure
11
Q
Describe intra-pleural fluid cohesiveness
A
The water molecules are attracted to each other and resist being pulled apart
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
13
Q
How do you convert mmHg to kPa?
A
divide by 7.5
14
Q
Is inspiration an active or passive process?
A
Active (depends on muscle contraction)
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.
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.
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.
18
Q
Is expiration an active or passive process?
A
passive (brought about by relaxation of inspiratory muscles)
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
20
Q
Define pneumothorax
A
Air in the pleural space
21
Q
Name three causes of a pneumothorax
A
- spontaneous
- traumatic
- iatrogenic
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
23
Q
What are the symptoms of a pneumothorax?
A
shortness of breath & chest pain
24
Q
What are the signs of a pneumothorax?
A
hyper-resonant percussion note & decreased/absent breath sounds
25
Name two factors that contribute to lung recoil
- elastic connective tissue
| - alveolar surface tension
26
Describe alveolar surface tension
attraction between water molecules at liquid air interface produces a force which resists the stretching of the lungs
27
What compound reduces surface tension?
Surfactant - mixture of lipids and proteins secreted by type II alveoli
28
According to the law of LaPlace what happens to smaller alveoli ?
They have a higher tendency to collapse
29
What does surfactant do?
Reduces the surface tension and prevents the small alveoli from collapsing & emptying their contents into the larger alveoli
30
Explain what is meant by alveolar interdependence
If an alveolus starts to collapse the surrounding alveoli are stretched and then recoil exerting expanding forces on the collapsing alveolus to open it.
31
What are the muscles of inspiration?
Major - diaphragm & external intercostal muscles
| Accessory - sternocleidomastoid, scalenus, pectoral
32
What are the muscles of expiration?
Abdominal & internal intercostal muscles
33
What is tidal volume?
Air in/out in a single breath - 0.5L
34
What is inspiratory reserve volume?
Extra volume that can be maximally inspired above the typical resting tidal volume - 3.0L
35
What is expiratory reserve volume?
Extra volume that can be expired by maximal contraction - 1L
36
What is residual volume?
Minimum volume of air remaining after maximal expiration - 1.2L
37
What is inspiratory capacity?
Maximum volume of air that can be inspired at the end of a normal quiet expiration 3.5L
38
What is functional residual capacity?
volume of air in the lungs at the end of normal passive expiration - 2.2L
39
What is vital capacity?
maximum volume of air that can be moved out during a single breath following maximal inspiration - 4.5L
40
What is total lung capacity?
total volume of air that the lungs can hold c. 5.7L
41
What happens to the elastic recoil when residual volume increases?
Recoil is lost e.g. emphysema
42
State the difference between FVC and FEV1
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)
43
What should FEV/FVC be greater than?
70%
44
How do you calculate flow?
change in pressure/resistance
45
Describe airway resistance
It is usually low and so air moves with a small pressure gradient. The primary determinant is the radium of the conducting airway
46
What does para/sympathetic stimulation do?
parasympathetic - bronchocontriction
| sympathetic - bronchodilatation
47
What is peak flow?
The speed at which someone can get air out of the lungs
48
What is pulmonary compliance?
Measure of the effort that has to go into stretching or distending the lungs
49
State five factors that decrease compliance
- pulmonary fibrosis
- pulmonary oedema
- collapsed lung
- pneumonia
- absence of surfactant
50
What is the effect of decreased compliance ?
Greater change in pressure is needed to produce a given change in volume and this causes shortness of breath
51
How is compliance increased?
By loss of elastic recoil in emphysema.
52
What is emphysema?
Narrowing of the alveoli
53
When is the work of breathing increased?
- decrease in compliance
- increase in airway resistance
- decrease in elastic recoil
- increase in need for ventilation
54
How do you calculate pulmonary ventilation?
tidal volume x respiratory rate
55
Define pulmonary ventilation
the volume of air breathed in and out per minute
56
How do you calculate alveolar ventilation?
(tidal volume - dead space) x respiratory rate
57
Define alveolar ventilation
the volume of air exchanged between the atmosphere and alveoli per minute
58
why is alveolar ventilation less than pulmonary ventilation?
Because of the presence of anatomical dead space
59
How can pulmonary ventilation be increased?
By increasing depth and rate of breathing
60
What two process does the transfer of gas between the body and atmosphere depend on?
Ventilation & Perfusion
61
Explain the difference between ventilation and perfusion
ventilation is the rate at which gas passes through the lungs whereas perfusion is the rate at which blood passes through the lungs
62
Describe alveolar dead space
Ventilated alveoli which are not adequately perfused with blood. In healthy people this is usually small and not important
63
State six things that happen when perfusion is greater than ventilation
- 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
State six things that happen when ventilation is greater than perfusion
- 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
Name four factors that influence the rate of gas exchange
- 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
Define partial pressure
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
Define diffusion coefficient
the solubility of gas in membranes
68
What are some other functions of the respiratory system?
- 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
What is Henry's Law?
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
Under resting conditions & strenuous exercise how much oxygen is taken to the tissues in dissolved form
15ml/min & 90ml/min
71
What is the resting oxygen consumption of our body cells?
250ml/min
72
How is most of the oxygen in the blood transported?
Bound to haemoglobin in red blood cells
73
What is the normal oxygen & haemoglobin concentration?
oxygen - 200ml/litre
| haemoglobin - 150g/litre
74
Describe the binding of oxygen to haemoglobin
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
What is the primary factor which determines the percent saturation of haemoglobin?
partial pressure
76
What shape is the curve produced which relates partial pressure to %Hb/oxygen concentration?
Sigmoid
77
Where can myoglobin be found?
Skeletal and cardiac muscles
78
What shape is the myoglobin dissociation curve what can be said about the affinity?
It is a hyperbolic curve and it has a higher affinity than haemoglobin but no cooperative binding
79
What does oxygen delivery to the tissues depend on?
Oxygen content of arterial blood
| Cardiac Output
80
What determines the oxygen content of arterial blood?
haemoglobin concentration
| saturation of Hb with oxygen
81
Name three ways by which oxygen delivery can be impaired
- respiratory disease
- heart failure
- anaemia
82
How is carbon dioxide transported?
10% solution
60% bicarbonate
30% carbamino compounds
83
Describe carbon dioxide in solution
The amount of gas dissolved is independent on the partial pressure. Carbon dioxide is 20x more soluble than oxygen
84
How is bicarbonate formed in the blood?
carbon dioxide + water --> Carbonic acid --> hydrogen ions + carbonate ions
85
What enzyme is invalid in bicarbonate formation? Where is bicarbonate found?
Carbonic anhydrase in red blood cells
86
Describe the movement of carbonate by the chloride shift
Carbonate is exchanged for chloride ions. The carbonate ion moves out of the red blood cell and chlorine moves in.
87
How are carbamino compounds formed?
By the combination of carbon dioxide with terminal amine groups in blood proteins.
88
What is the major blood protein that carbon dioxide binds to?
globin in haemoglobin
89
What is the Haldane Effect?
removing oxygen from Hb increases the ability to pick-up carbon dioxide and carbon dioxide generated hydrogen ions.
90
What is the Boher Effect?
removing the carbon dioxide/hydrogen ions from Hb increases the ability to pick-up oxygen
91
Define the rhythm
inspiration followed by expiration
92
Where is breathing rhythm generated?
Pre-Botzinger Complex
93
What is the Pre-Botzinger Complex?
Network of neutrons that display pacemaker activity, they are located near the upper end of the medullary respiratory centre
94
What does the pre-botzinger complex do?
Excites dorsal respiratory group neurones, leading to contraction of inspiratory muscles
95
What happens when firing of the dorsal group neurones stops?
Passive expiration occurs
96
Name the second group of neurones involved in respiration
Ventral respiratory group
97
How are the ventral respiratory group excited?
By increased firing of dorsal neurones
98
What happens as a result of excitation of the ventral group?
Forceful expiration, not in normal quiet breathing
99
How can the rhythm generated in the medulla be modified?
Neurones in the pons
- pneumotaxic centre
- apneustic centre
100
Describe the pneumotaxic centre, what happens without it?
stimulation terminates inspiration when dorsal respiratory neurones fire. Without it breathing is prolonged inspiratory gasps with brief expiration
101
Describe the apneustic centre
impulses from these neurones excite the inspiratory area of the medulla and prolong inspiration
102
where can stimuli that influence respiratory centres be found?
- higher brain centres
- stretch receptors
- J receptors
- joint receptors
- baroreceptors
- central chemoreceptors
- peripheral chemoreceptors
103
Give four examples of involuntary modifications of breathing
- pulmonary stretch receptors
- joint receptors reflex in exercise
- stimulation of respiratory centre by temperature, adrenaline or impulses
- cough reflex
104
Describe pulmonary stretch receptors
Activated during inspiration, afferent discharge inhibits inspiration. They do not switch off during normal respiration so prevent hyperinflation of the lungs
105
Describe joint receptors
impulses from moving limbs reflex increases breathing. They contribute to increased ventilation during exercise
106
name five factors that increase ventilation during exercise
1. relflexes
2. adrenaline release
3. impulses from cerebral cortex
4. increased body temperature
5. accumulation of carbon dioxide and hydrogen ions
107
Describe the cough reflex
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
Where is the cough reflex centre?
medulla
109
What are the two types of control of the respiratory system?
Neural
| Chemical
110
What are the two types of chemoreceptor?
- Peripheral
| - Central
111
Describe the peripheral chemoreceptors
in carotid & aortic bodies they sense tension of oxygen, carbon dioxide and concentration of hydrogen ions in the blood
112
Describe central chemoreceptors
near the surface of the medulla they respond to hydrogen ion concentration of the cerebrospinal fluid
113
What is the blood brain barrier?
relatively impermeable to hydrogen ions and carbonate ions, carbon dioxide readily diffuses
114
How does the CSF compare to blood?
It has less proteins and hence is less buffered
115
What happens when hypoxia occurs?
Neurones are depressed, the effect is via the peripheral chemoreceptors which are only stimulated when arterial oxygen falls to low levels
116
When might hypoxia occur?
- Patients with chronic carbon dioxide retention
| - High altitudes
117
What are the symptoms of altitude sickness>
```
Headache
Fever
Fatigue
Nausea
Tachycardia
Dizziness
SOB
Unconsciousness
```
118
Name five adaptations to high altitude
- increased RBCs
- increased 2,3 biphosphoglycerate
- increased number of capillaries
- increased number of mitochondria
- kidneys conserve acid to decrease arterial pH
119
Describe hydrogen ion drive
Central chemoreceptors are stimulated by hydrogen ions causing hyperventilation and increased elimination of carbon dioxide to adjust acidosis
