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Physiology Flashcards

1
Q

What is internal respiration?

A

The intracellular mechanisms which consume oxygen and produce carbon dioxide

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2
Q

What is external respiration?

A

The sequence of events that lead to the exchange of oxygen and carbon dioxide between the external environment and the cells of the body

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3
Q

What are the 4 steps of external respiration?

A

Ventilation
Gas exchange between alveoli and blood
Gas transport in the blood
Gas exchange at the tissue level

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4
Q

Describe ventilation (2)

A

The mechanical process of moving gas in and out of the lungs. Here, gas exchange occurs between the atmosphere and the air sacs in the lungs

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5
Q

In step 2 of external respiration, where is the gas exchanged?

A

Between the alveoli and the pulmonary capillaries

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6
Q

Describe the gas transport in the blood

A

The binding and transport of oxygen and carbon dioxide in the circulating blood

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7
Q

What are the 4 body systems involved in external respiration?

A

Respiratory
Cardiovascular
Haematology
Nervous

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8
Q

What physics law applies to ventilation and what does it entail?

A

Boyles Law - at any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas

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9
Q

What does Boyles Law mean practically?

A

As the volume of the gas increases, the pressure exerted by the gas decreases

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10
Q

What is key to remember with air flow in the respiratory system?

A

Moves down the pressure gradient from a region of high pressure to low pressure.

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11
Q

How does intra-alveolar pressure compare to atmospheric pressure and why?

A

Intra-avlevolar pressure is less than atmospheric as air will therefore move passively down the pressure gradient

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12
Q

How is a lower than atmospheric pressure achieved in the alveoli? (4)

A

Before inspiration, intra-alveolar pressure is the same as atmospheric
During inspiration, the thorax and lungs expand as a result of contraction of inspiratory muscles.
Therefore the volume in which the gas is distributed is greater
Therefore the pressure decreases

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13
Q

What are the two forces holding the lungs and the thoracic wall close together?

A

Intrapleural fluid cohesiveness

Negative intrapleural pressure

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14
Q

What intrapleural fluid cohesiveness?

A

The water molecules in the fluid between the two layers of pleural are attracted to each other and therefore resist being pulled apart

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15
Q

What is the negative intrapleural pressure?

A

Teh sub-atmospheric intrapleural pressure creates a transmural pressure graidient across the lung and chest wall, meaning they are forced to expand outwards while the chest is forced to squeeze inwards

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16
Q

Which force is more important out of the two forces that holds the lung and the thoracic wall together?

A

The negative intrapleural pressure

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17
Q

What are the intra-alveolar pressures pushing outwards and pushing inwards?

A

760mmHg outwards

756mmHg inwards

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18
Q

What does the difference in the inwards and outwards intra-alveolar pressures result in?

A

Transmural pressure gradient that pushes out on the lungs, stretching them to fill the thoracic cavity.

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19
Q

Which three pressures are important in ventilation?

A

Atmospheric
Intra-alveolar
Intrapleural

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20
Q

What is atmospheric pressure and what is its numerical value?

A

The pressure exerted by the weight of the gas in the atmosphere on objects - 760mmHg at sea level

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21
Q

What is the intrapleural pressure?

A

The pressure within the pleural sac (i.e. the pressure exerted on the outside of the lungs, within the thoracic cavity) - 756mmHg

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22
Q

What is inspiration?

A

The process of breathing in

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23
Q

What does inspiration depend on?

A

Muscle contraction

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24
Q

How does inspiration start? (2)

A

The volume of the thorax is increased vertically by the diaphragm contracting, and therefore flattening out its dome shape

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25
What are the nerves involved in diaphragmatic movement?
Phernic nerve from the cervical 3,4 and 5
26
how are the external intercostal muscles involved in inspiration?
They contract, lifting the ribs and moving the sternum upwards and outwards.
27
In which direction does the diaphragm move?
Downwards
28
When does air stop coming into the lungs on inspiration?
When the intra-alveolar pressure is equal to atmospheric pressure
29
How is expiration brought about?
By a relaxation of the inspiratory muscles
30
What type of process is inspiration?
Passive
31
What size do the organs of respiration end up after inspiration and why?
Their pre-inspiratory size due to the cell's elastic recoil
32
State the process of expiration
The contracted muscles relax and the elastic recoil of the chest wall and lungs make the intra-alveolar pressure increase This is due to there being a smaller volume in which the air is present This means that air will leave the lungs until the intra-alveolar pressure reaches atmospheric again
33
What is a pneumothorax?
Where there is air in the pleural space
34
What is the key thing that happens when there is a pneumothorax?
The transmural pressure gradient is abolished.
35
What happens (in terms of pressure) when there is a pneumothorax?
Air enters the pleural space to equalise the pressure difference between the lungs/atmosphere and the pleural space
36
What are the two types of pneumothorax?
Traumatic and Spontaneous
37
What is a traumatic pneumothorax?
When there is a puncture in the chest wall that permits air into the plural cavity
38
What is a spontaneous pneumothorax?
A hole in the lung wall that allows aur from the lung into the pleural space.
39
What is a collapsed lung?
When the transmural pressure gradient is abolished, meaning that all three pressures are equal.
40
What are the consequences of a collapsed lung?
The lung collapses to its unstretched size and the chest wall springs outwards
41
What are the two things that cause the lungs to recoil during expiration?
The elastic connective tissue in the lungs | The alveolar surface tension
42
What is the alveolar surface tension?
The force produced by the small water molecules that line the alveolar as they attract each other
43
What does the alveolar surface tension do?
Resist the stretching of the lungs
44
What would happen if the alveoli were lined purely with water?
The surface tension would be too strong and the alveoli would collapse
45
What type of alveoli have a higher tendency to collapse?
Ones with a smaller radius
46
What can be used to reduce the force of surface tension?
Surfactants
47
What are pulmonary surfactants made up of?
Complex mixture of lipids and proteins
48
What are pulmonary surfactants secreted?
Type II alveoli
49
How do pulmonary surfactants lower the surface tension?
It will sit in- between the water molecules, decreasing the attraction for each other
50
What does the alveolar surface tension ensure?
They lungs dont over expand
51
What is the effect of having surfactants in the alveoli?
They prevent smaller alveoli from collapsing and emptying their air contents into larger alveoli
52
When in the lifecycle are surfactants produced?
In later stages of pregnancy
53
What happens when a baby is born premature, in terms of their breathing?
They may not have enough pulmonary surfactants, causing respiratory distress syndrome
54
What is the sign the an infant is in respiratory distress syndrome and why?
Baby makes very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs
55
What is alveolar interdependence and why does it occur?
The alveoli are all interconnected When one alveoli starts to collapse, the others around it are stretched, and their elastic recoil brings the collapsed alveoli back into the right shape
56
State the 3 forces keeping the alveoli open?
Transmural pressure gradient Pulmonary surfactant Alveolar interdependence
57
State the 2 forces promoting alveolar collapse
Elasticity of stretched pulmonary connective tissue fibers | Alveolar surface tension
58
State the 6 muscles of inspiration and what each of them are used for
Sternocleidomastoid - forceful inspiration Scalenus - forceful inspiration Internal intercostal muscles - active expiration Abdominal muscles - active expiration External intercostal muscles - inspiration Diaphragm - inspiration
59
What is the tidal volume and what is its abbreviation?
The volume of air entering or leaving the lung in a single, passive breath - 500ml - TV
60
What is IRV?
Inspiratory Reserve Volume - the extra volume of air that can be maximally inspired on to of the tidal volume - 3000ml
61
What is the IC?
Inspiratory Capacity - Maximum volume of air that can be inspired at the end of a quiet, normal expiration. - 3500ml
62
How do you calculate the IC?
Tidal volume + Inspiratory Reserve Volume
63
What is the ERV?
Expiratory Reserve Volume - The extra volume of air that can be actively expired by maximal contraction beyond the normal volume of passive expiration - 1000ml
64
What is RV?
Residual Volume - minimum volume of air remaining in the lungs even after a maximal expiration - 1200ml
65
What is the FRC?
Functional Residual Capacity - Volume of air in the lungs at the end of a normal passive expiration - 2200ml
66
How do you calculate FRC?
Expired Reserve Volume + Residual Volume
67
What is the VC?
Maximum volume of air that can be moved out during a single breath following a maximal inspiration - 4500ml
68
How is the VC calculated?
Inspiratory Reserve Volume + Tidal Volume + Expiratory Reserve Volume
69
What cannot be measured on a spirogram?
Residual Volume
70
What is the Total Lung Capacity?
The maximum volume of air that the lungs can hold
71
How is the TLC calculated?
Vital Capacity + Residual Volume
72
What is the normal TLC?
5700ml
73
As you are unable to measure residual volume by spirometry, what cannot be calculated using a spirometry?
Total Lung Capacity
74
What happens to the Residual Volume when elastic recoil in the lungs is lost?
Residual volume increases
75
What three things does a Volume-Time curve from a spirometry reading allow you to determine?
Forced Vital Capacity Forced Vital Capacity in 1 second FEV1/FVC ratio
76
What is the FEV1/FVC ratio?
The proportion of the FVC that can be expelled in the first second of expiratrion
77
What is FVC?
Forced Vital Capacity - Volume of air that can be forcibly expelled from the lungs following a maximum inspiration
78
What two types of lung disease is spirometry useful in the diagnosis of?
Obstructive and Restrictive Lung disease
79
Compared to a normal spirometry, how does an obstructive lung disease one compare?
The FVC, FEC1 and FVC1/FVC is all low. It has a shallower slope, but reaches the same final FVC, just slower
80
What is the airway resistance normally like?
Very low and therefore air moves with a small pressure gradient
81
What is the equation that relates flow, pressure and resistance?
Flow = mean pressure/resistance
82
What is the primary determinant of airway resistance?
The radius of the airway
83
What part of the nervous system causes bronchoconstriction?
Parasymphathetic
84
What part of the nervous system causes broncoconstriction?
Symphathetic
85
What there is resistance to air flow, what part of breathing is difficult?
Expiration is more difficult than inspiration
86
What happens to intrapleural pressure during inspiration and expiration?
Inspiration - pressure falls | Expiration - Pressure rises
87
What is dynamic airway compression?
When rising pleural pressure during active expiration compresses the alveoli and airway
88
Why is dynamic airway compression useful?
When applied to the alveolus, it helps push air out the lungs
89
Why is dynamic airway compression not desirable in the airways? (2)
It tends to compress the airway, and in patients with obstruction, the diseased airway is more likely to collapse.
90
Does dynamic airway compression cause a problem in normal people?
No
91
What are two diseases that cause an obstruction of the airway?
COPD and Asthma
92
Detail what happens during dynamic airway compression in patients with an obstruction
The driving pressure between the alveolus and airway is lost at the obstruction Therefore there is a fall in airway pressure along the airway downstream Resulting in the airway being compressed by the rising pleural pressure
93
How can the problem with patients with obstructive lung disease and dynamic airway compression become worse? What happens because of this? (4)
If the patient also has decreased elastic recoil of the lungs. They often lose the ability to push air out of their lungs, meaning it is more difficult for them to breathe out, increasing their residual volume and hyper-inflating the lungs
94
What does a peak flow rate assess?
Airway function
95
When is a peak flow test useful?
In patients with obstructive lung disease
96
What two factors makes peak flow measurements vary?
Age and height
97
What does good pulmonary compliance mean?
You can inflate your lungs easily
98
What is compliance the measure of?
The effort that has to go into stretching or distending the lungs
99
What are the units of compliance?
Volume change per unit pressure change across the lungs
100
What does it mean if the lungs are less compliant?
More work is required to produce a given degree of inflation
101
State 5 factors that decrease lung compliance
``` Pulmonary fibrosis Pulmonary oedema Lung collapse Pneumonia Absence of surfactant ```
102
What symptom is caused by decreased pulmonary compliance and why?
Shortness of breath (particularly on extertion)as a greater pressure is needed to produce a given change in volume
103
What happens structurally to the lungs (in general) when pulmonary compliance decreases?
They become stiffer
104
What pattern would decreased pulmonary compliance cause on spirometry?
A restrictive pattern
105
In what situation does the pulmonary compliance increase?
If the elastic recoil of the lungs is lost
106
What disease causes increased pulmonary compliance?
Emphysema
107
What happens physically to patients with increased pulmonary compliance?
Patients have to work harder to get the air out of the lungs, so they therefore hyper-inflate
108
What increases pulmonary compliance in everyone?
Age
109
State the 4 situations when the work of breathing is increased
When pulmonary compliance is decreased When airway resistance is increased When elastic recoil is decreased When there is a need of increased ventilation
110
What is anatomical dead space?
Areas in the lungs where air is present but there is no gas exchange occuring
111
What is the equation for pulmonary ventilation, and the units?
Tidal volume x Respiratory Rate = L/min

RM Respiratory (2 decks)

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