Respiratory Physiology Flashcards
1
Q
The main function of the respiratory system is to maintain
A
normal arterial oxygen and carbon dioxide content
2
Q
Are the mechanisms used to maintain normal arterial oxygen and carbon dioxide the same?
A
Most of them are but not all
3
Q
True/False? Lung compliance alters ventilation?
A
True
4
Q
List the functions of the respiratory System
A
Gas Exchange, Acid Base Balance, protection from infection, communication via speech
5
Q
What is acid-base balance in the respiratory system?
A
acid base balance is the maintenance of the pH of extracellular fluid at a value of 7.4.
6
Q
Which other system does the respiratory system work with in order to maintain the body pH?
A
Renal System
7
Q
What percent of acid base balance is achieved through changes in the respiratory system?
A
50%
8
Q
How does the respiratory system protect one from infections?
A
the respiratory epithelia has a dense concentration of immune tissue present within it that constantly scans the air we inhale looking for pathogens against which it would set up an immune response. The respiratory epithelia also has a dense cilia network that is responsible for beating any large inhaled particles up the respiratory tract and away from the deep lung tissues.
9
Q
if you inhale smoke or very fine dust particles, then they will get trapped in
A
mucus
10
Q
___________ beats mucus up the respiratory tract and away from the delicate alveolar tissues
A
cilia
11
Q
How is the respiratory system involved in speech?
A
air moving through our vocal cords in our larynx, cause those vocal cords to vibrate
12
Q
Do we speak on inhalation or exhalation?
A
Exhalation
13
Q
Why do we need oxygen?
A
To produce energy
14
Q
Can humans produce energy anaerobically? If so, is it sufficient to meet the resting energy demand of the body?
A
Yes, the body can produce energy anaerobically but however, it is not enough to meet the resting energy demand of the body.
15
Q
Type of respiration that occurs out in the periphery is called?
A
Cellular/Internal respiration
16
Q
External respiration is the movement of gases between
A
the air and the body’s cells
17
Q
Name the 2 circulatory systems
A
Pulmonary and systemic circulations
18
Q
When you’re exercising, you have an increase in energy demand of
A
your working skeletal muscle
19
Q
Why is there an increase in the rate and depth of breathing when exercising?
A
To speed up substrate (oxygen) acquisition and expel carbon dioxide
20
Q
net volume of gas exchanged in the lungs per minute
A
250 mLs oxygen and 200 mLs carbon dioxide
21
Q
Why is it important that the amount of gas that we are exchanging at the lungs is equal to the volume of gas being exchanged at the tissues?
A
because it prevents gas build-up in the circulation that could hamper gas exchange or to maintain the concentration gradient difference between the lungs and the blood
22
Q
Which one is higher? PCO2 in cells or PCO2 in systemic arterial blood?
A
PCO2 in cells
23
Q
Why do we feel more comfortable breathing with our nose than with our mouth?
A
The nose has a larger surface area to volume ratio which is much better at warming and moistening the air.
24
Q
Why does the air have to be moistened before reaching the lungs?
A
air we breathe has to be fairly saturated with water vapour because the air needs to be in solution in order to diffuse from the lungs into the blood.
25
What is the pharynx most commonly known as?
Throat
26
A tube that connects the back of your nose and the back of your mouth and joins with the larynx or splits to form the oesophagus
Pharynx
27
common conduit shared with the digestive system
Pharynx
28
What is the epiglottis?
A flap of cartilaginous tissue
29
When is the epiglottis open and when is it closed?
Open when breathing and closed when eating
30
How does the epiglottis close?
when we swallow small muscles around the larynx act to cause the epiglottis to close
31
The biggest Airway?
Trachea
32
Sternal angle location?
Between jugular notch and sternum
33
At which point does the trachea split?
From underneath the sternal angle
34
How many times does the left and right primary bronchi divide?
24 times
35
Where does the upper respiratory tract end?
Below the larynx, above the ribcage
36
Part of the upper respiratory system that isn't also shared with the alimentary system?
Larynx
37
Which fissure can be found in both lungs?
Oblique
38
Oblique fissure in the right lung divides
Middle and inferior lobes
39
Horizontal fissure in the right lung divides
Superior and middle lobes
40
Oblique fissure in the left lung divides
Superior and inferior lobes
41
How many secondary bronchi can be found in the right lung?
3, one in each lobe
42
How many secondary bronchi can be found in the left lung?
2, one in each lobe
43
Secondary bronchi branch to give
tertiary bronchi
44
We have one tertiary bronchi or bronchus going to
each bronchial pulmonary segment of the lung
45
The lung as well as being split into lobes, is further split into
bronchial segments
46
What is the function of c-shaped, cartilaginous rings?
helps maintain patency of trachea and bronchi by giving some degree of rigidity that stops them from collapsing or compressing
47
What is patency?
by patency, we mean that the airway is open and air can flow freely along it.
48
Why is it important to maintain a patent or clear airway?
So that ventilation and movement of air to and from the lungs can take place unimpeded.
49
How many generations of branching do we have from the trachea to the level of alveoli?
24
50
How do we maintain the patency of bronchioles?
By the physical forces of the thorax
51
At any one time, how much air sits in the dead space?
150 mL
52
Compare the right and left primary bronchi
The right primary bronchi is slightly more wider than the left The right primary bronchi has a more vertical trajectory than the left primary bronchi making it easier for aspirated foreign bodies to get stuck in the right bronchi
53
Compared to the angle to the right lung, the angle to the left lung is more
acute
54
Compared to the angle to the left lung, the angle to the right lung is more
obtuse
55
The difference in angles to both the lungs is due to
the trachea being acute
56
Airways where no gaseous exchange occur fall under which zone?
Conducting zone
57
Airways where gaseous exchange occur fall under which zone?
Respiratory zone
58
Bronchioles split into how many generations?
12
59
First division within the respiratory tree
Primary bronchi
60
Second division within the respiratory tree
Secondary bronchi
61
Third division within the respiratory tree
Tertiary bronchi
62
As we move down our respiratory tree, the diameter of the airways
decreases
63
According to physics, what happens to resistance as diameter decreases?
increases
64
What happens to resistance as airway diameter decreases?
decreases
65
Why does airflow down the respiratory tree not obey the resistance laws in physics?
When looking at resistance and diameter in the respiratory tree, we look at the cross-sectional area instead of airway diameter. The cross-sectional area is much greater in the lower parts of the respiratory tree compared to the trachea or upper parts of the respiratory tree.
66
Why is there an increase in resistance as you go up the respiratory tree?
While diameter increases as you go up the respiratory tree, the increase in diameter is not proportional to the number of air molecules that are trying to move through it and as a result we get an increase in resistance.
67
In which zone of the respiratory tract, does the dead space occur?
Conducting zone
68
How can the diameter of the bronchial airways change?
The bronchial smooth muscle can relax or contract.
69
What would happen to resistance if the bronchial smooth muscle contracts (diameter decreases)?
Increase
70
Which nervous system acts on bronchial smooth muscles?
Sympathetic Nervous system
71
The sympathetic nervous system acts on _________ receptors
Beta receptors (Beta-2 because we have 2 lungs)
72
What happens to bronchial smooth muscle when adrenaline or noradrenaline binds to beta-2 receptors?
Relax (increase diameter of bronchiole)
73
When the sympathetic system kicks in, the bronchial smooth muscles relax causing the bronchioles to
Dilate
74
What happens to ventilation when bronchioles dilate?
Maximised
75
What accommdates the alveoli with inflation during inspiration?
Elastic fibres
76
When is energy stored in elastic fibres and how is it used?
Energy is stored in the elastic fibres during alveoli inflation and is used during expiration to squeeze the alveoli and force air out since expiration at rest is passive.
77
Which type of cells make up the bulk of the alveolar wall and what is its function?
Type 1 alveolar cells are responsible for gas exchange
78
Type 1 cells are studded with yellow ________ cells
Type 2
79
Type 2 cells are responsible for
Surfactant secretion
80
Do type 2 cells play a role in gas exchange?
No
81
Capillaries are directly abutted with
Type 1 cells
82
Why are capillaries never sitting adjacent to type 2 cells?
Because they are not responsible in gas exchange
83
Why do elastic fibres never sit between type 1 cells and capillary cells?
To minimise the distance required for gases to travel and diffuse
84
\_\_\_\_\_\_\_\_are dotted all around the respiratory system to combat infections
Macrophages
85
To help boost the immune function of the lung, _____ are present in the connective tissue of the lungs
Alveolar macrophages
86
If you flatten out all the alveoli, it will cover about
80m^2 (size of a badminton court)
87
Each lung has a capacity of about
3 L
88
Thickness of the alveoli
one cell thick
89
At the end of a normal inspiration, our lungs contain ___ L of air
2.8
90
Normal amount of air we breathe in and out is ___ mL and is referred to as the _____ volume
500, tidal
91
Amount of air left in the lungs at the end of a normal relaxed expiration is referred to as the \_\_\_\_\_\_\_
Functional residual capacity`
92
The biggest breath that we can take on top of our normal tidal volume is a volume of about __ L
3
93
The extra air that we can breathe in is referred to as the
Inspiratory reserve volume
94
Extra air that we can expire with a bit more effort is called the
expiratory reserve volume
95
Expiratory reserve volume is about __ L
1
96
Maximum amount of air that we can expire after a maximum inspiration is known as the
vital capacity
97
Vital capacity manoeuvre is often used in
respiratory physiology and clinical respiratory physiology to measure lung function
98
Volume vs. Capacity
A capacity involves a number of different volumes added together
99
Vital capacity involves the volumes of
Inspiratory reserve volume, tidal volume and expiratory reserve volume
100
\_\_\_\_\_\_\_ volume is the amount of air left in the lungs after a maximum expiratory effort and is usually about __ L
Residual, 1.2
101
Residual volume is important because
it stops the alveoli from collapsing even after the elastic fibres recoil and it provides a volume of air that can allow a gas exchange to take place between breaths
102
What would happen if the alveoli completely collapsed?
It would take an awful lot of energy to inflate them again in the next breath
103
The 150 mL of air in dead space is part of the
Tidal volume
104
The _____ of the lungs is the point at which the lungs connect with the major airways or the airways are leaving or entering those lungs
hilum
105
How much fluid can be found in each pleural cavity?
3 mL
106
The pleural cavity is surrounded by the
Pleural membrane
107
Pleural membrane has 2 aspects named
Parietal and visceral membranes
108
The parietal pleural membrane is the membrane that is
closest to the ribs and attached to the superior surface of the diaphragm
109
The visceral pleural membrane is the membrane that is
attached to the outer surface of the lungs and goes into all the fissures
110
The pleural fluid creates a _____ force that allows the two pleural membranes to glide across each other
Cohesive
111
The cohesive force of the pleural fluid ensures the lungs are effectively stuck to the
ribcage and diaphragm
112
Visceral pleura is stuck to the parietal pleura through the
cohesive forces of the pleural fluid
113
Functions of pleural fluid
- Stops the lungs from recoiling by limiting recoiling of the elastic fibres by cohesive forces of the pleural fluid - Allows friction free movement of lungs across the ribcage as we breathe in and out
114
Why do we feel 'comfortable' at the end of a normal expiration?
Because an equilibrium is reached between the elastic fibres wanting to recoil and the chest wanting to expand further.
115
Pneumothoraxes commonly occur due to
penetrating wounds to the chest wall that allow air to enter the pleural cavity
116
What happens when air enters the pleural membrane?
we lose the cohesive force in the pleural fluid because the air forces them apart
117
What happens to lung function in relation to chest wall in a pneumothorax?
Lung functions independently
118
Boyle's law states that
the pressure exerted by a gas is inversely proportional to its volume
119
Dalton's law states that
the total pressure of a gas mixture is the sum of the pressures of the individual gases
120
Charles' law states that
the volume occupied by a gas is directly related to the absolute temperature
121
In vivo, Charles' law is not applied as much because
the temperature in the human body is constant at 37 degree Celsius
122
Any given volume will measure a greater amount in a warm room because
gas molecules move about more when they are hot
123
Henry's Law states that
the amount of gas dissolved in a liquid is determined by the pressure of the gas and it's solubility in the liquid
124
Which law governs the movement of air during inspiration and/or expiration?
Boyle's Law
125
Breathing happens because
the thoracic cavity changes volume
126
What happens to the pressure inside the thoracic cavity when the volume inside the thoracic cavity increases?
Decreases
127
Which muscles are used upon inspiration?
External intercostals and diaphragm
128
Which muscles are used during severe respiratory load or forced expiration?
Internal intercostal muscles and abdominal muscles
129
Main muscle in respiration responsible for about 70 percent of the muscular activity of inspiration
Diaphragm
130
External intercostal muscles run between
the ribs
131
During normal relaxed inspiration, are the scalene and sternocleidomastoid muscles used?
Rarely
132
When and how are scalene and sternocleidomastoid muscles used in respiration?
During severe respiratory load, these muscles act on the upper ribs and clavicle to lift them up for expiration. It also aids in chest wall expansion to get extra amounts of air into the thoracic cavity during inspiration.
133
True/False: When the abdominal muscles contract, they directly act on the thoracic cavity and not the abdominal cavity
False
134
What happens to the volume of the abdominal cavity when the abdominal muscles contract?
Decreases
135
Where do the organs of the abdominal cavity go when the volume of the abdominal cavity decreases?
They get pushed up against the diaphragm which pushes up into the thoracic cavity (decreasing thoracic cavity volume)
136
When we start to inspire the _____ nerve innervates the diaphragm causing it to contract
phrenic
137
The diaphragm _________ at inspiration causing an increase in thoracic cavity volume
Flattens down
138
The diaphragm _________ at expiration causing a decrease in thoracic cavity volume
relaxes
139
The diaphragm is aided by the
intercostal muscles
140
The external intercostal muscles act to
raise the sternum and expand the ribs
141
There is an increase in\_\_\_\_\_\_\_\_\_ dimensions of the thoracic cavity when the external intercostal muscles lift up the sternum and the ribs
posterior
142
The external intercostal muscles increase thoracic cavity volume in which 3 dimensions?
Anterior, posterior and lateral
143
The internal intercostal muscles act to
push the sternum in and the ribs down
144
The internal intercostal muscles lie at ___ degrees to the external intercostal muscles as they run between the ribs
90
145
List the pressures of the thoracic cavity
Intra-thoracic (alveolar) pressure [PA] Intrapleural Pressure [Pip] Transpulmonary Pressure [PT]
146
What is Intra-thoracic (alveolar) pressure [PA]?
pressure inside the thoracic cavity, essentially pressure in the lungs. May be positive or negative compared to atmospheric pressure
147
When is alveolar pressure positive?
When the atmospheric pressure is less than alveolar pressure
148
What is Intrapleural Pressure [Pip]?
pressure inside the pleural cavity, typically megative compared to atmospheric pressure (at least in healthy lungs)
149
What is Transpulmonary Pressure [PT]?
difference between alveolar and intrapleural pressures. Almost always positive.
150
True/False: In health. Intrapleural Pressure is always more negative than alveolar pressure?
True
151
What is the normal intrapleural pressure?
-3mmHg
152
Why is intrapleural pressure negative?
pleural membranes are constantly being pulled apart ever so slightly by the recoil of the lungs and the expansion of the chest
153
What is surfactant?
Detergent-like fluid produced by type 2 alveolar cells.
154
How does surfactant help the alveoli?
It reduces surface tension on the alveolar surface membrane thus reducing the alveoli's tendency to collapse.
155
When does surface tension occur?
It occurs wherever there is an air-water interface
156
Where does the air-water interface occur at the alveolar level?
Thin film of water on the surface of the alveoli to saturate the air in the alveolar sac before it can diffuse into the blood
157
How can the thin fluid film of water around the alveoli cause the alveoli to collapse?
The water molecules around the alveoli are attracted to each other thus creating a force or inwardly directed pressure that could cause the alveoli to collapse by pulling it into the middle
158
How does surfactant help the thin fluid film from causing the alveoli to collapse?
Surfactant reduces the attraction between the water molecules by sitting between them and therefore reducing the surface tension.
159
Surfactant increases
Lung compliance
160
What is Lung compliance?
It is a measure of lung distensibility/stretchibility
161
Increased lung distensibility makes it easier to get air
into the lungs
162
Surfactant is more effective in small/large alveoli?
Small
163
Why is surfactant more effective in small alveoli?
Because surfactant molecules are more concentrated in small alveoli.
164
Surfactant and surface tension obey the law of
LaPlace
165
Law of LaPlace states that the pressure required to keep an alveoli open is equal to
2T/r
166
Does the surface tension differ between smaller and larger alveolus? Why?
No because the droplets of water are attracted to each other with the same attractive force
167
Does surfactant equalize or create pressure differences among small and large alveolus?
Equalize
168
When does surfactant production start in the womb?
25 weeks gestation
169
When is surfactant production complete in the womb?
36 weeks gestation
170
Full gestation period in a human is
40 weeks
171
Production of which hormones stimulate surfactant production?
Thyroid hormones and hormone cortisol (both of which are significantly increased towards the end of pregnancy)
172
Babies that are born before 36 weeks tend to have inadequate amounts of surfactant. This causes
Infant Respiratory Distress Syndrome (IRDS)
173
IRDS causes _____ such that \_\_\_\_\_\_\_\_\_
breathing difficulties; premature babies have to overcome the surface tension and have to invest a big amount of energy to inflate their alveoli
174
IRDS can be treated with
synthetic surfactant aerosols
175
Does it take more pressure to fill the lungs with saline or air?
Air
176
Just like us, babies in utero go through the same breathing cycle. What do they breathe in to fill their lungs given the fact that they are still incapable of putting the effort needed to breathe normally?
Uterine fluid (effectively saline)
177
Define compliance
Compliance is a term that defines a change in volume relative to a change in pressure
178
Compliance does not measure elasticity. It measures
stretchability, how easy it is to inflate the lungs (get air into the lungs NOT out)
179
High compliance refers to
healthy lungs where there is a large increase in lung volume for a small decrease in intrapleural pressure
180
A disease where patients have highly compliant lungs but lost elasticity
Emphysema
181
Low compliance refers to
a small increase in lung volume for a large decrease in intrapleural pressure
182
A disease where the lungs have low compliance
Fibrosis
183
Does anatomical dead space volume differ at different times?
Anatomical dead space volume is relatively fixed for any one individual
184
Ventilation refers to
movement of air (not specified) in and out of lungs (Breathing)
185
Ventilation can be described in two ways, namely
- Pulmonary (Minute) ventilation - Alveolar ventilation
186
Pulmonary (Minute) ventilation refers to
total air movement into/out of lungs (relatively insignificant in functional terms)
187
Alveolar ventilation refers to
fresh air getting to alveoli and therefore available for gas exchange (functionally much more significant)
188
Alveolar ventilation is very significantly impacted by
anatomical dead space
189
Both pulmonary and alveolar ventilation are measured in
litres per minute
190
What percent of normal tidal breathing is efficient? Where does the rest go?
70%; stuck in dead space
191
Can alveolar ventilation change? If so, how?
Yes, alveolar ventilation can vary depending on our breathing pattern and this can be for the better or for the worse
192
Average normal respiratory rate of an ideal man is
12 breaths/min
193
`Tidal volume of an ideal man is
500 mL
194
What happens to our respiratory rate and tidal volume when we are anxious?
Respiratory rate increases (20 breaths/min) and tidal volume decreases (300mL) (fast, shallow breaths)
195
What happens to our respiratory rate and tidal volume when we are sleeping or in a chilled out state?
Respiratory rate drops (8 breaths/min) and tidal volume increases (750 mL)
196
Pulmonary ventilation (mL/min) =
Tidal volume (mL) \* Respiratory rate (breaths/min)
197
Air to alveoli (mL) =
Tidal volume (mL) - Dead space volume (mL)
198
Alveolar Ventilation (mL/min) =
Air to alveoli (mL) \* Respiratory rate (breaths/min)
199
Most efficient way of breathing is by
breathing deeply
200
Best way to enhance alveolar ventilation
breathing deeply and rapidly (i.e. when you exercise)
201
What happens to alveolar ventilation if you increase respiratory rate but keep the tidal volume the same?
Increases
202
Hypoventilation refers to
low alveolar ventilation
203
Hyperventilation refers to
high alveolar ventilation
204
What is the composition of the air we breathe in? Where does the carbon dioxide in our body come from?
79% nitrogen, 21% oxygen, and 0.03% Carbon dioxide The carbon dioxide found in our blood and cells is made by us and is a by-product of aerobic respiration.
205
Partial pressure can be defined as
the pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture.
206
Partial pressure of the oxygen we breathe in =
21% \* 760mmHg = 160mmHg
207
True/False: All gas molecules exert the same pressure.
True
208
What happens to partial pressure if there is an increase in concentration of gas mixture?
Increases
209
Normal alveolar ventilation is about
4.2 L
210
Partial pressure of oxygen at normal alveolar ventilation
100 mmHg / 13.3 kPa
211
Partial pressure of carbon dioxide at normal alveolar ventilation
40 mmHg / 5.3 kPa
212
What is the air that we breathe in diluted by?
Anatomical dead space, residual volume, and water vapour
213
Are the partial pressure values in the alveoli the same as the partial pressure values in systemic arterial blood? If so why?
Yes, because both diffuse until equilibrium is reached.
214
What happens to oxygen in hypoventilation?
It is metabolised by the peripheral tissues faster than it is being replenished
215
What happens to partial pressure of oxygen in hyperventilation?
Increases
216
What is our primary driving force for breathing?
Carbon dioxide
217
Why is chronic hyperventilation difficult to keep up?
Because you have to consciously always overcome your brain
218
As we breathe in, intrapleural pressure becomes (more/less) negative.
more
219
The more negative intrapleural pressure becomes, the ______ the transpulmonary pressure becomes.
becomes
220
True/False: For any given change in pressure, we get a bigger change at the base than at the apex of the lung.
True
221
Alveolar pressure is the greatest at the (base/apex) of the lung
base
222
As height increase (from base to apex), what happens to alveolar ventilation?
declines
223
Why does alveolar ventilation decrease with height?
Because compliance is lower at the apex of the lung than it is at the base.
224
When a patient is lying down, where do you expect to have more alveolar ventilation?
Back of the lung
225
Branch of systemic circulation that delivers nutritive blood supply to the lungs is known as the
bronchial circulation
226
What does the bronchial circulation supply and remove the lung tissue with/from?
Supplies with nutrients, enzymes, and hormones Removes waste products
227
Bronchial circulation comprises about ___ % of left heart output
2
228
Blood from bronchial veins drains to the ________ via the \_\_\_\_\_\_\_\_\_\_\_
left atrium; pulmonary veins
229
Bronchial circulation veins are
systemic veins
230
\_\_\_\_\_\_\_\_\_\_\_\_ carries the entire cardiac output from the right ventricle
Pulmonary artery
231
Pulmonary circulation is in _______ with systemic circulation
series
232
What does "pulmonary circulation is in series with systemic circulation" mean?
The volume of blood that goes through the pulmonary circulation per minute is the same volume of blood that goes around the rest of the body in one minute
233
Pulmonary circulation is a ____ flow, ____ pressure system
high, low
234
Systolic over diastolic pressure in pulmonary circulation is
25/10
235
Systolic over diastolic pressure in systemic circulation is
120/80
236
There is a very ____ pressure gradient driving blood from the right side of the heart to the left side of the heart.
low
237
Is the pressure gradient lower from the right side of the heart to the left or from the left side of the heart to the right?
Right side of the heart to the left
238
PAo2 stands for
Alveolar Po2
239
Value of Alveolar Po2
100 mmHg / 13.3 kPa
240
PACO2 stands for
Partial pressure of Carbondioxide in alveoli (Alveolar PCO2)
241
Value of Alveolar PCO2
40 mmHg / 5.3 kPa
242
PaO2 stands for
Partial pressure of oxygen in arterial blood (Arterial PO2)
243
Value of arterial PO2
100 mmHg / 13.3 kPa
244
PaCO2 stands for
Arterial pressure of carbondiaoxide (Arterial PCO2)
245
Value of arterial PCO2
40 mmHg / 5.3 kPa
246
PVO2 stands for
Partial pressure of oxygen in mixed venous blood (Venous PO2)
247
Value of Venous P02
40 mmHg / 5.3 kPa
248
PVCO2 stands for
Partial pressure of carbondioxide in mixed venous blood (Venous PCO2)
249
Value of Venous PCO2
46 mmHg / 6.2 kPa
250
Arterial blood values reflect
lung values
251
Mixed venous blood values reflect
tissue values
252
Relationship between diffusion and partial pressure gradient
Directly proportional
253
Relationship between diffusion and gas solubility
directly proportional
254
Relationship between diffusion and available surface area
directly proportional
255
Relationship between diffusion and membrane thickness
inversely proportional
256
Relationship between diffusion and short distances
diffusion is rapid over short distances
257
True/False: Oxygen is very soluble in water
False
258
True/False: Carbondioxide is very soluble in water
True
259
Why is it that when it comes to diffusion, the pressure difference between oxygen is much higher than that of carbondioxide?
Because carbondioxide is very soluble in water compared to oxygen
260
What happens in emphysema?
Destruction of surface area available for gas exchange which then reduces the rate of diffusion needed for adequate gas exchange leading to less oxygen entering the blood (low PO2 in pulmonary vein and systemic arterial blood and low PCO2 in pulmonary artery)
261
What happens in fibrosis?
Fibrous tissue is laid out alongside elastic tissue between Type 1 cell and capillary cell causing the lung's connective tissue to end up with both fibrous and elastic tissue which then leads to a thick alveolar membrane slowing down gas exchange. The fibrous tissue impedes diffusion as well as resists stretch making lung expansion difficult lowering lung compliance and decreasing partial pressure gradient (less oxygen/carbondioxide goes into/out of the blood).
262
What is pulmonary hypertension?
An increase in blood pressure in the pulmonary capillaries forcing plasma out of the capillaries to sit in the interstitial space.
263
What happens in pulmonary edema?
Usually comes about as a result of pulmonary hypertension forcing plasma out of the capillaries and cools in the interstitial space increasing the distance between the alveoli and blood vessel. The fluid creates a pressure that resists inflation of the alveoli. Partial pressure of oxygen decreases since oxygen cannot easily dissolve in water while partial pressure of carbondioxide usually remains the same. It affects diffusion rather than compliance or ventilation.
264
What happens in asthma?
Asthma affects ventilation rather than diffusion. In asthma, there is no diificulty in gases diffusing but however there is a low partial pressure of oxygen and this is because there is not enough oxygen available in the first place for diffusion. Asthma causes an inappropriate constriction of the bronchial smooth muscle or inflammation of the bronchioles thus impeding ventilation.
265
Apart from asthma, what other diseases affect ventilation?
Emphysema and fibrosis
266
The X-Ray of a patient with fibrosis would show
radiopaque fibres
267
How does smoking cause emphysema?
Constituents within cigarette smoke activate an enzyme called elastase that break down elastic fibres and the alveolar wall resulting in a loss of surface area and elasticity
268
Define Obstructive lung disease
Obstruction of airflow, especially during expiration
269
Define Restrictive lung disease.
Restriction of lung expansion as a result of loss of lung compliance
270
What happens in chronic bronchitis?
Inflammation of the bronchi that narrows the airways compromising airflow.
271
Chronic bronchitis and emphysema fall under the umbrella
Chronic Obstructive Pulmonary Disease (COPD)
272
COPD and Asthma are classified as
Obstructive lung diseases
273
There is about _______ people worldwide estimated to have COPD in a moderate to severe form.
80 million
274
About ___ percent of the UK's population has moderate to severe COPD
1
275
It is suspected that there is a high prevalance of COPD in individuals over the age of \_\_\_
75
276
What is an idiopathic condition?
A condition where the origin of the disease is not specified or unknown.
277
True/False: Fibrosis is an idiopathic condition
True
278
For every 100,000 people, there is about ___ new cases of fibrosis every year in the UK
50
279
Name and explain a class of fibrosis.
Asbestosis; occurs when exposed to asbestos dust for a long period of time
280
What is spirometry?
Spirometry is a technique commonly used to measure lung function producing either static or dynamic measurements. It is a commonly used technique in the clinical respiratory physiology lab.
281
Static spirometer measurements consider
exhaled/inhaled volume
282
Dynamic spirometer measurements consider
the time taken to inhale/exhale a certain volume of what is being measured
283
Most clinical respiratory lung function tests work with
expired air
284
Name the lung volumes that can be measured by spirometry.
Any lung volume that does not involve residual volume (cannot be expired) can be measured by spirometry, i.e. tidal volume, inspiratory reserve volume, expiratory reserve volume, inspiratory capacity, and vital capacity
285
Common lung function test carried out with spirometry
FEV1/FVC
286
What is FEV1? What is its value in a fit, healthy, young male?
FEV1 refers to the forced expiratory volume in 1 second; 4 litres
287
What is FVC? What is its value in a healthy, young, adult male?
The total amount of air that you can expire over whatever time (sees how fast you can push the air out); 5 litres
288
What is the FEV1/FVC ratio in a healthy person regardless of age, gender, or sex?
80%
289
What does an FEV1/FVC ratio of 80% mean?
A healthy person is able to expire about 80% of their vital capacity in the first second when an FVC maneuver is performed.
290
Why is the FEV1 decreased in restrictive lung diseases when there is no problem expiring?
Because there is less air in the lungs in the first place.
291
True/False: In restrictive lung diseases, FEV and FVC ratios are reduced in proportion to a much greater extent than in obstructive lung diseases
True
292
Possible reasons for why expiring air can be challenging in obstructive lung diseases
- Increase in resistance in the airways
- Loss of pressure normally generated in the alveoli by contraction of elastic fibres
293
What happens to functional residual capacity in patients with obstructive lung disease? Why?
Increases because they start retaining more air as they can't expire most air out
294
Is spirometry more useful in diagnosing restrictive or obstructive lung diseases? Why?
More useful to diagnose obstructive lung diseases
Little to no use to diagnose restrictive lung diseases as these patients could have a normal FEV1/FVC ratio
295
At what point of inspiration is compliance low? How does it increase?
The start; it increases by big changes in intrapleural pressure in the beginning.
296
At what point of expiration is compliance low? How does it increase?
The start; it increases when intrapleural pressure reaches about -0.4kPa towards the end end of expiration
297
Why do the inspiratory and expiratory curves not superimpose?
- During inspiration, we need to overcome lung inertia (the tissue's reluctance to change shape )
- Overcome surface tension that causes the alveoli to collapse
During expiration, pressure increases (making intrapleural pressure less negative) to push air out
298
Decreased compliance curve looks
less steep than normal
299
Perfusion refers to
blood flow through pulmonary circulation (or) local blood flow
300
What does our body ideally want in terms of ventilation and perfusion? Do we get it?
Ideally, our body would like the amount of air getting into the lungs per minute to be equal to the amount of blood flowing past the lungs per minute.
We, however, do not get it as there is a ventilation-perfusion mismatch
301
Ventilation and perfusion across all the lung\_\_\_\_\_\_\_\_\_. With height, ventilation and perfusion \_\_\_\_\_.
do not precisely match; decreases
302
At the base of the lung, blood flow is ______ than ventilation because
higher; arterial/blood pressure exceeds alveolar pressure compressing the alveoli
303
At the apex of the lung, blood flow is ______ than ventilation because
lower; arterial pressure is less than alveolar pressure compressing the arterioles
304
At which part of the lung are ventilation and perfusion equal?
Rib 3 (V/Q ratio 1)
305
At which part of the lung do we have the greatest ventilation-perfusion mismatch?
Apex
306
With height, blood flow ______ faster than ventilation
declines
307
In the upright position, the ventilation-perfusion ratio _______ with height
increases
308
The base of the lung is normally poorly ventilated which is minimal. In what extreme cases is this poor ventilation beyond the minimum?
- Blockage of an upper airway due to aspiration of a foreign body
- Lung tumour compressing one of the upper airways, secondary or tertiary bronchi, or one of the upper bronchioles
309
Poorly ventilated alveoli tend to have a build-up of
carbon dioxide
310
What causes a fall in PO2 in poorly-ventilated alveoli?
Oxygen is used up faster in poorly-ventilated alveoli than being replenished leading to a fall in its partial pressure. Keep in mind that oxygen needs a big partial pressure gradient in order to diffuse.
311
What happens when carbondioxide starts to build-up in the alveoli?
We will lose the partial pressure gradient that pulls carbon dioxide out of the blood and cannot replenish the blood with oxygen. We end up sending this blood back to the heart through the pulmonary vein diluting it with blood from better-ventilated alveoli.
312
Blood flowing past the poorly ventilated alveoli is being ________ from the right side of the heart without undergoing gas exchange.
shunted
313
How does the body minimize the effects of a shunt in pulmonary circulation?
In response to a decrease in PO2 or hypoxia, the smooth muscle in the blood vessels around poorly ventilated alveoli constrict redirecting the blood to better-ventilated regions of the lung.
314
How does the body combat hypoxia in systemic circulation?
If there is a region in the periphery that is hypoxic, the systemic vessels dilate so that it can deliver oxygen to that region.
315
Constriction in response to hypoxia is absolutely unique to _____ blood vessel
pulmonary
316
What happens to ventilation and perfusion in poorly ventilated alveoli?
An increase in PCO2 causes the bronchial smooth muscle to dilate increasing ventilation while constriction of blood vessels reduces perfusion in an effort to bring the V/Q ratio close to 1.
317
When ventilation exceeds blood flow, we get \_\_\_\_\_\_\_\_\_\_
alveolar dead space that cannot participate in gas exchange due to low perfusion
318
'Ventilation \> perfusion' normally occurs at the apex. It happens to a greater extent in pathological situations like
pulmonary embolism where there is a blood clot in one of the pulmonary vessels impeding blood flow
319
What does it mean by alveolar dead space is opposite to shunt?
In shunt, perfusion exceeds ventilation while in alveolar dead space, ventilation exceeds perfusion
320
Why do we get a decrease in PCO2 in alveolar dead space?
Because we are blowing off carbon dioxide faster than it is added to the alveoli due to a reduction in blood flow bringing a mild bronchial constriction
321
An increase in PO2 leads to
pulmonary vasodilation
322
The biggest contributor to physiologic dead space is
anatomical dead space
323
In pulmonary embolism, anatomical dead space
increases
324
Normal change in heart rate during the breathing cycle is known as
Respiratory Sinus Arrhythmia
325
Borometry trace going up signifies
breathing in
326
Borometry trace going down signifies
breathing out
327
As you breathe in, heart rate
goes up
328
True/False: dogs have a stronger sinus rhythm arrhythmia than humans
true
329
Sinus arrhythmia is important because
it helps minimise ventilation-perfusion mismatch
330
What would happen if heart rate stayed constant during inspiration? Why?
increased alveolar dead space due to increased ventilation than perfusion
331
What would happen if heart rate stayed constant during expiration? Why?
increased shunt due to perfusion being greater than ventilation
332
\_\_\_\_\_\_\_\_\_\_\_\_\_\_ innervates the heart
Parasympathetic vagus nerve
333
What happens to vagal nerve activity when heart rate goes up?
Decreases
334
\_\_\_\_\_\_ slows down the heart rate
Vagal nerve
335
Decrease in vagal nerve activity occurs when heart rate goes up. How?
Removing brake on heart rate
336
What happens to vagal nerve activity when heart rate goes down? How?
Increases by outting the brakes on hearet rate
337
Oxygen travels in 2 forms in the blood, namely:
- In solution in plasma
- Bound to haemoglobin within RBC
338
How much and why does very little oxygen travel in plasma?
3 mL oxygen per litre of plasma; Because plasma is 95% water making it harder for oxygen to dissolve.
339
How much oxygen is present in whole blood?
200 mL per litre
340
How much oxygen is bound to haemoglobin?
197 mL
341
Why is it important to have this little amount of oxygen inplasma?
Because it determines how much oxygen binds to haemoglobin
342
How does carbon dioxide travel?
It travels in one form or the other in plasma since it is soluble in water
343
The bulk of carbon dioxide travels in the form of
bicarbonate ions
344
How much CO2 is transported in solution in plasma and how much is stored in haemoglobin?
77% in solution in plasma
23% stored in haemoglobin
345
What does partial pressure in the alveoli reflect?
systemic arterial blood
346
What does partial pressure in pulmonary arteries reflect?
Partial pressure at tissues
347
What are the typical partial pressure values for oxygen and CO2 in alveoli?
100 mmHg Oxygen
40 mmHg Carbon dioxide
348
What are the typical partial pressure values for oxygen and CO2 in the pulmonary arteries?
40 mmHg Oxygen
46 mmHg Carbon dioxide
349
PO2 in plasma should be the same as PO2 in
alveoli
350
How do values of partial pressure of gases in solution compare to the partial pressure in gaseous phase that is driving the gas into solution?
equal
351
Our cardiac output at rest is
5 L per minute
352
O2 delivery to tissues =
Arterial O2 content \* Cardiac Output
353
If the heart pumps 5 litres of blood per minute, how much oxygen would be delivered to our tissues given that there are no red blood cells or haemoglobin oresent?
Cardiac output = 5L/min
Arterial O2 content = 3mL/min
Oxygen delivered = 3\*5 = 15 mL/min
354
How much is the oxygen demand for resting tissues?
250 mL/min
355
What percentage of arterial O2 is extracted by peripheral tissues at rest?
25%
356
True/False: At rest, we are delivering way more oxygen than needed to the periphery
True
357
98% of the oxygen carried in the blood is carried in
haemoglobin
358
Most haemoglobin in adult blood is in the form of
Haemoglobin A
359
Haemoglobin A contains
4 polypeptide chains, 2 alpha chains and 2 beta chains
All the chains are associated with a haem group
360
Each molecule of haemoglobin has ___ haem groups
4
361
In the centre of the haem group, an ______ atom can be found. Each of these atoms will associate with one oxygen molecule.
Iron
362
True/False: Each red blood cell can only carry 4 molecules of oxygen.
False. Each red blood cell is jam-packed with hemoglobin.
363
Association between oxygen and iron atom with the haem group is known as
oxygenation reaction
364
Oxygenation reaction vs. oxidation reaction
Oxygenation reaction is weaker
365
Oxygen binds to iron
weakly
366
When oxygen binds to haemoglobin, it causes polypeptide chains to shuffle because
making it easier for other oxygen molecules to bind
367
How does haemoglobin bind to oxygen?
Cooperatively binds to 4 oxygen molecules
368
What is meant by cooperative binding in haemoglobin?
When one oxygen molecule starts to leave, it encourages the other oxygen molecules to leave.
369
The major detriment of the degree to which haemoglobin binds or is saturated with oxygen is the
partial pressure of oxygen in the blood and amount of oxygen in plasma
370
Partial pressure of oxygen is determined by
how much oxygen is in solution
371
Partial pressure of oxygen in the plasma is the same as the partial pressure of oxygen in the
alveoli
372
Partial pressure of oxygen in the alveoli is determined by
alveolar ventilation
373
Why does the partial pressure of oxygen not change as hemoglobin binds to it?
It effectively hides it from the plasma, maintaining the partial pressure gradient that continues to suck O2 out of alveoli until Hb becomes saturated
374
Haemoglobin binds to oxygen to form
oxyhemoglobin
375
When is saturation of haemoglobin complete?
After 0.25 seconds of contact with alveoli
376
What is the total contact time between haemoglobin and alveoli?
0.75 seconds
377
The relationship between PO2 and the saturation of haemoglobin results in a
sigmoidal curve
378
How saturated in haemoglobin at a PaO2 of 60 mmHg?
90%
379
How saturated in haemoglobin at a PaO2 of 40 mmHg?
75%
380
What is normal venous PO2?
40 mmHg
381
What happens to the affinity of haem groups for oxygen when the partial pressure of oxygen drops below 60?
decreases
382
What is anaemia?
Any condition where the oxygen carrying capacity of blood is compromised
383
What are some examples of anaemia?
Iron deficiency
Hemorrhage
Vitamin B12 deficiency
384
Vitamin B12 is necessary because
it produces red blood cells
385
Is it possible for red blood cells to be fully saturated with oxygen in anaemia? Why?
Yes, because the major detriment of oxygen saturation of haemoglobin is partial pressure of oxygen.
386
What factors affect the affinity of haemoglobin for oxygen?
pH
PCO2
Temperature
387
How does pH affect affinity?
A decrease in pH decreases affinity
388
How does PCO2 affect haemoglobin affinity for oxygen?
An increase in PCO2 decreases affinity
389
How does temperature affect haemoglobin affinity for oxygen?
390
How does an increase in affinity impact collecting and depositing oxygen?
Makes collecting easier but depositing harder
391
What is the Bohr effect?
for any given partial pressure of oxygen, the haemoglobin becomes less saturated with oxygen when there is a decrease in pH or increase in PCO2.
It aids oxygen unloading at peripheral tissues.
392
How does a decrease in pH affect extracellular fluid?
Makes it acidic
393
In acidosis, the curve shifts to the right. How does this affect the normal 25% oxygen delivery to tissues?
Tissues get more than the usual 25%
394
When the affinity of haemoglobin for oxygen decreases, oxygen delivery to tissues
increase
395
A complication of hypothermia
peripheral tissues cannot access oxygen in the blood
396
What can bind to haemoglobin to decrease its affinity for oxygen?
2, 3 - diphosphoglycerate (2,3 - DPG)
397
Red blood cells start to produce more ___________ in situations of hypoxia.
2,3 diphosphoglycerate
398
What synthesises 2,3 - diphosphoglycerate (2,3 - DPG)?
Erythrocytes
399
When does 2,3 - diphosphoglycerate (2,3 - DPG) increase and why?
Situations associated with inadequate oxygen supply (such as heart or lung disease, living at a high altitude) to help maintain oxygen release in tissues
400
Why does carbon monoxide cause problems?
It binds to haemoglobin with an affinity 250x greater than oxygen
401
What does carbon monoxide form when it binds to haemoglobin?
Carboxyhaemoglobin
402
When does carbon monoxide bocome problematic?
As soon as it dissolves in plasma
403
What PCO causes progressive carboxyhaemoglobin formation?
0.4 mmHg
404
What are the symptoms of too much carbon monoxide?
Hypoxia
Anaemia
Nausea
Headaches
Cherry red skin and red mucous membranes
Brain damage
Death
405
What happens to respiration rate in patients with too much carbon monoxide?
unaffected
406
What is hypoxia?
Deficiency in the amount of oxygen reaching tissues
407
How is carbon dioxide transported in the blood?
7% remains dissolved in erythrocytes and plasma
23% combines in the erythrocytes with deoxyhaemoglobin to form carbamino compounds
70% combines in the erythrocytes with water to form carbonic acid which dissociates to yield bicarbonate and H+ ions
408
What happens to most of the bicarbonate within red blood cells?
Moves out of the cell into the plasma in exchange for Cl- ions and excess H+ ions bind to deoxyhaemoglobin
409
What is bicarbonate leaving erythrocytes for Cl- called?
Chloride shift
410
411
The partial pressure of oxygen refers to
oxygen in solution in plasma
412
What happens to excess H+ ions after carbonic acid dissociates into bicarbonate and H+ ions?
Bind to deoxyhaemoglobin
413
Where does carbon dioxide bond to compounds to be broken down, and where is it built up?
Dissolved and made into other substances in systmemic capillaries
Built up from these substances in pulmonary capillary to be diffused into the alveoli lumen
414
Why is normal pH stable althoug carbon dioxide is broken down into H+?
All the carbon dioxide produced is eliminated in expired air
415
When would the pH not be stable due to carbon dioxide?
During hypo/hyperventilation as it alters plasma PCO2 and plasma [H+] will vary
416
What does hypoventilation do the the amount of carbon dioxide in the blood and [H+]?
CO2 retention
Increased [H+] bringing about respiratory acidosis
417
What brings about respiratory acidosis?
Hypoventilation (retention of carbon dioxide)
418
What does hyperventilation do to the amount of carbon dioxide in the blood and [H+]?
Blowing of more CO2
Decreased [H+] bringing about respiratory alkalosis
419
What brings about respiratory alkalosis?
Hyperventilation (blowing of more CO2)
420
How much oxygen dissolve in 1 litre of water?
0.03 mLs
421
What is PaO2 determined by?
O2 solubility and the partial pressure of O2, in the gaseous phase that is driving O2 into solution
422
How do values of partial pressure of gases in solution compare to the partial pressure in gaseous phase that is driving the gas into solution?
They are equal
423
If 3ml of oxygen is present per litre of plasma, what is the partial pressure that is driving O2 into the loquid phase in plasma?
100mmHg
This is because solubility of water is 0.03ml/L/mmHg (3/0.03 = 100)
424
425
How many oxygen molecules are in 1 litre of gas?
30 times more than in 1 litre of plasma
426
True/False: concentration of oxygen molecules per litre is different in the gaseous phase than the liquid phase
true
427
True/False: partial pressure of oxygen molecules per litre is different in the gaseous phase than the liquid phase
false
428
If we get gas in the blood, then we get
an air embolism
429
What is the partial pressure of oxygen also known as?
oxygen tension
430
How does PO2 in the liquid phase compare to that in the gaseous phase, and to the concentration in the liquid phase?
PO2 is the same in the liquid phase as the gas phase
PO2 in the liquid phase is different from the concentration as that varies depending on what phase the gas is in
431
Why do some divers get air embolisms?
Sometimes divers ascend from depth too quickly causing more air to be pushed into the liquid phase (arterial bloodstream) than it normally would at sea level leading to nitrogen gas bubbles in their tissues and bloodstream.
432
What percent of haemoglobin is not in adult form?
8%
433
How much oxygen binds to each gram of haemoglobin?
1.34 mL
434
How much oxygen can be found in 1L of systemic blood?
200 mL
435
What are some forms of haemoglobin other than HbA?
HbA2 (δ chains replace β)
HbF (γ chains replace β)
Glycosylated Hb (HbA1a, HbA1b, HbA1c)
436
What happens to beta chains in HbA2?
Replaced with delta chains
437
What happens to beta chains in foetal haemoglobin (HbF)?
replaced with gamma chains
438
Glycosylated Haemoglobin is really important
clinically
439
What is glycosylated hemoglobin used for?
monitoring diabetes and blood glucose control in diabetes
440
When does hemoglobin become glycosylated?
When it is exposed to high levels of glucose.
441
Red blood cells have a life span of about
120 days
442
Name the haemoglobin (not necessarily a type but a distant cousin!) found in skeletal and cardiac muscle.
Myoglobin
443
When can myoglobin be found in the circulation?
When there is extensive muscle damage
444
Compare and contrast between hemoglobin and myoglobin.
Both are oxygen-carrying molecules
Haemoglobin transports oxygen while myoglobin stores oxygen
445
Which one has a higher affinity for oxygen; Haemoglobin or myoglobin?
Myoglobin
+ foetal haemoglobin
446
Structurally, how do haemoglobin and myoglobin differ?
Both contain haem groups to which oxygen binds
Myoglobin contains 1 polypeptide chain while hemoglobin contains 4 polypeptide chains
447
How does the affinity of foetal haemoglobin (HbF) and myoglobin for oxygen compare to HbA?
They are higher which is necessary for extracting oxygen from maternal arterial blood
448
True/False: The affinity of the foetal haemoglobin is greater than the maternal haemoglobin
True
449
Importance of foetal haemoglobin.
access maternal haemoglobin
450
What are the 5 main types of hypoxia?
Hypoxaemic hypoxia
Anaemic hypoxia
Stagnant hypoxia
Histotoxic hypoxia
Metabolic hypoxia
451
What is hypoxaemic hypoxia?
Reduction in oxygen diffusion at lungs either due to decreased PO2atmosphere or tissue pathology
452
What is anaemic hypoxia?
Reduction in oxygen-carrying of blood due to anaemia, such as red blood cell loss or iron deficiency
453
What is stagnant hypoxia?
Heart disease results in inefficient pumping of blood to lungs/around the body
454
What is histotoxic hypoxia?
Poisoning prevents cells utilising oxygen delivered to them, such as carbon monoxide or cyanide
455
What is metabolic hypoxia?
Oxygen delivery to the tissues does not meet increased oxygen demand by cells
456
What stimulation does ventilatory control require?
Stimulation of skeletal muscles of respiration
457
Skeletal muscles of inspiration are innervated by ________ nerve which supplies the diaphragm and the _________ nerves which supply the external intercostal muscles.
phrenic; intercostal
458
Is there any neural input to muscles of expiration? Why or why not?
No because expiration is normally passive
459
Where does ventilatory control reside?
With ill-defined centres (respiratory centres) found in the pons and medulla
460
Ventilatory control is entirely dependent on
signalling from the brain
461
The phrenic nerve is made up of cervical nerves
C3, C4, and C5
462
What can you say about the conscious level required to breath?
In subconscious but can be voluntaraly modulated
463
Where must the spinal cord be severed for breathing to stop?
Above the origin of the phrenic nerve (C3)
464
Like the intrinsic rhythm to the heart, is there an intrinsic rhythm to the muscles of breathing?
no
465
What would happen if you cut the nerve input to the heart?
It will continue to beat as long as there is a blood and nutrient supply.
466
How are muscles of respiration activated?
Input of the somatic motor neuron
467
What would happen if you cut the somatic motor neuron?
respiratory muscles will not contract therefore breathing ceases
468
Which stimuli can alter the rhythm of respiratory centers in the brain stem?
emotions
469
Which system does emotion reside in?
Limbic system
470
In which part of the brain does voluntary, conscious thought originate?
Cortex
471
What do respiratory centres have their rhythm modulated by?
Emotion (via limbic system of the brain)
Volunrary over ride (via higher centres in the brain)
Mechano-sensory input from thorax (such as stretch reflex)
Chemical composition of the blood detect by chemoreceptors (PCO2, PO2 and ph)
472
Explain mechano-sensory input from the thorax.
Refers to stretch receptors that exist in the thoracic cage monitoring how much the thoracic wall is stretching. When a threshold is reached in terms of stretch, we get a reflex inhibition of ventilation (safety mechanism from overinflation of the alveoli)
473
How does the chemical composition of blood alter respiratory rhythm?
Chemoreceptors detect PO2, PCO2, and pH of systemic arterial plasma
474
Name the 2 group of neurons that can be found in the respiratory centers.
Dorsal Respiratory Group (DRG)
Ventral Respiratory Group (VRG)
475
What do the dorsal respiratory group of neurons innervate?
Inspiratory muscles via the phrenic and intercostal nerves
476
DRG neurons are involved in
setting up stimulation of inspiratory muscles, diaphragm, and external intercostal muscles
477
What does the ventral respiratory group of neurons innervate?
Tongue
Pharynx
Larynx
Expiratory muscles
478
VRG neurons are involved in
stimulating contraction or basal muscular tone of tongue, pharynx, larynx, and expiratory muscles
479
Why is it important to have VRG neuron to maintain a basal tone?
Because it helps maintain a patent airway or the pharynx, larynx, tongue, and expiratory muscles would collapse
## Footnote
*during normal expiration, the Ventral Respiratory Group maintains its basal tone in the tongue, pharynx and the larynx (EXPIRATORY MUSCLES ONLY DURING RESP. LOAD)*
480
What happens to DRG during expiration?
It switches off
481
What happens to expiratory muscles during relaxed expiration?
Not being used but helps maintain basal tone
482
Name the 2 types of chemoreceptors.
Central and peripheral
483
Where are central chemoreceptors?
Medulla
484
What do central chemoreceptors respond to?
Directly to H+ (directly reflects PCO2 by binding to H+)
Changes in [H+] in CSF
485
What do central chemoreceptors provide?
Primary ventilatory drive
486
Where are peripheral chemoreceptors?
Carotid and aortic bodies
487
What do peripheral chemoreceptors respond to?
Changes in PO2 and changes in plasma [H+]
488
What do peripheral chemoreceptors provide?
Secondary ventilatory drive
489
How does the cerebrospinal fluid differ from interstitial fluid?
Cerebrospinal fluid has a much more tighter composition that interstitial fluid does elsewhere in the body
The brain is much less tolerant of changes in the composition of the fluid that bathes it than other tissues are.
490
How is the composition of the cerebrospinal fluid regulated?
By the blood-brain barrier
491
How do central chemoreceptors respond to changes in [H+] in the CSF around the brain?
Reflex stimulation of ventilation in response to an increase in [H+)
492
What is hypercapnia?
Abnormally elevated levels of carbon dioxide in the blood
493
What is the process of central chemoreceptor altering ventilation?
1) Arterial PCO2 increases and carbon dioxide crosses the blood-brain barrier (not H+)
2) Bicarbonate and H+ are formed and receptors respond to H+
3) Feedback via the respiratory centres increases ventilation in response to increased arterial PCO2
4) Decreased arterial PCO2 slows ventilation rate
5) This means that the central chemoreceptors monitor the PCO2 indirectly in the cerebrospinal fluid
494
What type of feedback loop is the response to an increase in PCO2?
Leads to an increase in ventilation
Negative feedback loop
495
Patients with chronic lung disease are on hypoxic drive rather than hypercapnia drive. What do these patients rely on?
Their central chemoreceptors become desensitized to the increased stimulation of PCO2. They then start to rely instead on their peripheral chemoreceptors and respond to changes in the partial pressure of oxygen and also to changes in hydrogen ion concentration.
496
Why are peripheral chemoreceptors termed as peripheral?
Because they are found in the carotid artery and aorta
497
Peripheral chemoreceptors don't do much until your PO2 falls to
60 mmHg
498
What is the process of peripheral chemoreceptors altering ventilation?
1) Arterial PO2 is low so no oxygen combines with an oxygen sensor
2) K+ channel closes so the cell depolarises
3) Exocytosis of dopamine-containing vesicles
4) Act on dopamine receptors on sensory neuron
5) Action potential generated that signals medullary centres to increase ventilation
499
When would peripheral chemoreceptor stimulate ventilation?
Plasma pH falls ([H+] increases)
During acidosis
500
When would peripheral chemoreceptor inhibit ventilation?
When pH rises ([H+] decreases)
During alkalosis or vomiting
501
What can voluntary descending neural pathways from the cerebral cortex not override?
Involuntary stimuli such as arterial PCO2 or [H+]
502
Why is respiration inhibited during swallowing?
Avoid aspiration of foods or fluids into the airways, followed by an expiration in order than any particles are dislodged outwards from the region of the glottis
503
What are common drugs that affect respiratory centres?
Barbiturates and opioids
Gaseous anaesthetic agents
Nitrous oxide
504
How do barbiturates and opioids affect respiratory centres?
Depress respiratory centres, overose often results in death as a result of respiratory failure
505
How do gaseous anaesthetic agents affect respiratory rate?
Increase respiratory rate, but decreases tidal volume
506
Hows does nitrous oxide affect respiratory centres?
Blunts peripheral chemoreceptor response to falling PaO2
507
How safe is using nitrous oxide on respiratory centres?
Very safe in most people
Problematic in chronic lung disease cases where individual often on hypoxic drive and administering O2 to these patients aggravates situation
508
What causes an increase of [H+] in the blood?
Rise in arterial PCO2
CO2 + H2O ↔ H2CO3 ↔ HCO3 + H+
509
Difference between the peripheral chemoreceptors responding to hydrogen ions and the central chemoreceptors responding to hydrogen ions
peripheral chemoreceptors will respond to hydrogen ions that are generated by any means (i.e. lactic acid) so they don't have to originate from carbon dioxide. Whereas the hydrogen ions that the central chemoreceptors are responding to always have to originate from carbon dioxide.
510
As hydrogen ion concentration increases and our pH decreases, we will get a ______ increase in ventilation
Linear
511
The muscles of inspiration and expiration are
All skeletal muscle and under voluntary control
512
513
514
515
516
517
