physiology Flashcards
1
Q
what is internal respiration?
A
intracellular mechanism of which consumes oxygen and produces co2
food + oxygen = energy + carbon dioxide (+ water)
2
Q
what is external respiration?
A
the 4 sequence of events that lead to the exchange of O2 and co2 between the external environment and the cells of the body
3
Q
what are the steps of external respiration?
A
- ventilation- air in and out of lungs
- gas exchange between alveoli and blood
- exchange of o2 in alveoli - gas transport in the blood- binding of o2 and co2 to blood
- gas exchange at tissue level
4
Q
what 4 systems are involved in external respiration?
A
- respiratory system
- cardiovascular system
- haematology
- nervous system
5
Q
what is boyle’s law?
A
at a constant temp- as the volume of the gas increases the pressure of the gas decreases.
6
Q
what must happen to intra-alveolar pressure in order for air to flow into the lungs during inspiration?
A
intra-alveolar pressure must be lower than atmospheric pressure.
7
Q
how does air flowing into the lungs occur?
inspiration
A
Rib cage expands and moves upwards
caused by contraction of the diaphragm - increases volume of thorax
and external intercostal muscles- contracts and lifts ribs and sternum
8
Q
what are the two forces which hold the thoracic wall and the lungs in close opposition?
A
- intrapleural fluid cohesiveness- water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart. Keeps pleural membrane together
- negative intrapleural pressure- sub atmospheric intrapleural pressure creates a transmullar pressure gradient across the lung wall and also the chest wall.
9
Q
What are the main pressures involved in pulmonary ventilation?
A
- Atmospheric pressure at sea level
- intra-alveolar pressure- pressure within the lung alveoli
- intrapleural pressure- pressure exerted outside the lungs but within the pleural cavity
10
Q
What are the usual pressure values of these pressures
A
- atmospheric pressure- 760 mm Hg
- intra-alveolar- when equal to atmospheric pressure it is 760 mm Hg
- Intra pleural- 756 mm Hg
11
Q
what is the name of the mechanism describing the movement of external intercostal muscles during inspiration?
A
bucket handle mechanism
12
Q
what nerves supply the diaphragm?
A
phrenic nerve from C3,4,5
13
Q
what does inspiration do the intra alveolar pressure?
A
makes it decrease due to increase size of lungs= more volume
14
Q
what is the difference between inspiration and expiration in regards to the process?
A
inspiration is active- requires contraction of muscles
(normal) expiration is passive- relies on relaxation of inspiratory muscles
15
Q
when the diaphragm relaxes what causes the lungs decrease in size during expiration?
A
its elastic recoil properties from the elastic connective tissue
alveolar surface tension( most important factor)
16
Q
what happens to the intra alveolar pressure during expiration?
A
increase due to decrease in volume. Pressure rises above atmospheric pressure allowing for expiration
17
Q
what is transmural/transpulmonary pressure?
A
It is the difference in pressure between the alveolar and pleural pressures.
18
Q
what is alveolar surface tension?
A
The characteristic of water particles on the surface to have a strong attraction to water particles on the inner surface due to cohesion.
19
Q
what reduces alveolar surface tension?
A
surfactant
20
Q
what is a surfactant
A
A mixture of Phospholipids, proteins, and ions. It is a surface-active agent of water.
21
Q
where is pulmonary surfactant secreted from?
A
Type ii alveolar epithelial cells. These cells are granular.
22
Q
What is la place’s law?
A
P= 2T/r where: P = inward directed collapsing pressure T = surface tension r = radius of the alveoli
23
Q
what does la place’s law suggest?
A
smaller the alveoli the bigger the risk of it collapsing
24
Q
why are surfactants so important?
A
prevents smaller alveoli collapsing and emptying contents into larger alveoli
25
besides from transmural pressure and pulmonary surfactant what other major force tries to keep alveoli open?
alveolar interdependence
26
what is alveolar interdependence?
When a collapsing alveolus stretches the ones around it.
This in turn causes the alveoli surrounding it to recoil and pull it open.
27
what are the accessory muscles of inspiration?
sternocleidomastoid - lifts the sternum
pectoral
scalenus
28
when are accessory muscles used for inspiration
during forceful inspiration
29
what are the muscles of active expiration?
1. Abdominal muscles 2. Internal intercostal muscles
30
What is the tidal volume? (TV)
ii. what is its average value ( in a young adult male)
volume of air entering or leaving lungs during a single breath
ii. 0.5 L
31
what is the inspiratory reserve volume?
ii. average value?
extra volume of air that can be maximally inspired over and above the typical resting tidal volume
ii. 3.0 L
32
what is the expiratory reserve volume?
ii. average value?
extra volume of air that can be maximally actively expired over and above the typical resting tidal volume
ii. 1.0 L
33
what is the residual volume?
ii. average value?
minimum volume of air remaining in the lungs even after a maximal expiration
ii. 1.2 L
34
What is the definition of inspiratory capacity?
ii. average value?
maximum volume of air that can be inspired at the end of a normal expiration.
ii. 3.5 L
35
how do you calculate the inspiratory capacity?
Tidal volume plus the inspiratory reserve volume
36
what is the Functional residual capacity?
ii. average value?
volume of air in lungs at end of normal passive expiration.
ii. 2.2 L
37
how do you calculate the FRC?
expiratory reserve volume plus the residual volume.
38
what is the vital capacity?
ii. average value?
maximum volume of air that can be moved out during a single breath following a maximal inspiration
ii. 4.5 L
39
How do you calculate the VC?
inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume.
40
What is the total lung capacity?
ii. average value?
Total volume of air in the lungs
ii. 5.7 L
41
How do you calculate TLC?
you can't their effect on the pop scene is unquantifiable
Vital capacity+ residual volume
42
when does the residual volume increase?
when elastic recoil of the lung is decreased
43
why can't TLC be measured by a spirometry?
because the residual volume cannot be recored by a spirometry. you need the RV to calculate the spirometry
44
What is the function of a volume time curve?
allows you to calculate Forced vital capacity (FVC) and forced expiratory volume in one second ( FEV1)
45
what is FEV1?
volume of air that can be expired during the first second of expiration in an FVC determination
46
What is the FEV1/FVC ratio?
proportion of the FVC that can be expired in the first second
47
What equipment is used to calculate volume time curve?
spirometry
48
What is the normal % of a FEV1/FVC ratio?
ii. what does it suggest if this value is below this number?
>70%
ii. obstructive lung disease
49
what is the main role of parasympathetic stimulation on the airways?
bronchoconstriction
50
what is the main role of sympathetic stimulation on the airways?
bronchodilation
51
How do you calculate airway resistance
Flow= change in pressure/resistance
52
why is there only a small pressure gradient in the airway for air movement?
as resistance to flow is very low
53
what happens to intrapleural pressure in:
1. inspiration
2. expiration
1. decrease
| 2. increase- causes dynamic compression
54
what is the effect of dynamic airway compression?
not effective on normal people
only effects patients with obstructive lung disease by making it harder to actively expire
55
what does dynamic airway compression effect? ( anatomically speaking)
compresses alveoli and airway
compressing alveoli- helps push air out
compressing airway- a nuisance!
56
why does obstructive lung disease not benefit from dynamic compression?
the driving pressure between the alveolus and airway is lost over the obstructive segment.
causes fall in airway pressure resulting in airway compression from the pleural pressure
57
what is a peak flow meter?
records peak flow rate-measures the maximum speed at which a patient can move air out of lungs
58
what is the peak flow rate?
assesses the airway function
useful for obstructive lung disease
59
what is lung compliance?
The ability for the lungs to expand/stretch and how much effort is required.
i.e. less compliance= more effort required for the lungs to stretch
60
what factors decrease lung compliance?
Pulmonary fibrosis
Pulmonary oedema
Lung collapse
Pneumonia
lack of surfactant
61
Decreased pulmonary compliance has what effect on pressure difference in the lungs?
Greater pressure difference needed to change volume of lungs
62
what effect has lung compliance have on a volume time curve?
shows patient to have restrictive patterns
63
why might abnormal increase of lung compliance occur?
ii. what is this common in?
loss of elastic recoil of the lungs
ii. emphysema- hyperinflation of lungs
64
compliance increases with age true or false?
true
65
when does work of breathing increase?
decrease in lung compliance
decrease in elastic recoil
increase in airway resistance
when lungs are required to increase ventilation
66
what is Anatomical dead space?
the non exchange areas where air may remain in the respiratory system
67
what is pulmonary ventilation?
volume of air breathed in and our per minute
68
what is alveolar ventilation?
volume of air exchange between the atmosphere and alveoli per minute
represents new air available of gas exchange with blood
69
How do you calculate pulmonary ventilation?
Tidal volume x Respiratory rate= PV (L/min)
70
What is the normal respiratory rate?
12-20 breaths per minute
71
How do you calculate alveolar ventilation?
(Tidal volume-dead space)x respiratory rate
72
why does alveolar ventilation have a lower value than pulmonary ventilation?
As it takes into consideration anatomical dead space
73
Because of anatomical dead space what should you do to increase pulmonary ventilation?
increase the depth of breathing (Increase Tidal volume)
74
what is the difference between ventilation and perfusion?
Ventilation: rate at which gas is passing through the lungs (rate of airflow)
perfusion: rate at which blood is passing through the lungs (rate of blood flow)
75
what is alveolar dead space?
refers to alveoli with poor ventilation or perfusion
76
Accumulation of CO2 in alveoli due to increase perfusion causes what?
decreased airway resistance= increased airflow
77
Increase in alveolar O2 concentration as a result of increased ventilation causes what?
pulmonary vasodilation
increased blood flow
78
What factors occur when Perfusion is greater than ventilation?
CO2 increases in area
O2 decrease in area
dilation of local airways
Constriction of local blood vessels
Airflow increase
Blood flow decrease
79
What factors occur when ventilation is greater than perfusion?
Co2 decreases in area
O2 increase in area
constriction of local airways
dilation of local blood vessels
airflow decrease
blood flow increase
80
what is the difference between Physiological and anatomical dead space?
ii. is there a difference in value?
Physiological dead space includes alveolar dead space. (Anatomical dead space + alveolar dead space)
Anatomical dead space does not
ii.In healthy individuals the values are equal. However, Unhealthy individuals can have physiological dead space being 1 to 2 litres greater.
81
What happens to pulmonary and systemic arterioles during:
1. Decreased O2
2. Increased O2
1. Pulmonary: vasoconstriction
Systemic: Vasodilation
2. Pulmonary: Vasodilation
Systemic: vasoconstriction
82
What are the four factors which effect the rate of Gas exchange across the alveolar membrane?
1. Partial Pressure gradient of O2 and CO2
2. Diffusion coefficient of O2 and Co2
3. Surface area of alveolar membrane
4. thickness of alveolar membrane
83
What is Dalton's law of partial pressure?
Total pressure exerted by gaseous mixture= sum of the partial pressures of each individual component in the gas mixture
P total = P1 + P2 + P3...)
84
What is the partial pressure of a gas?
The pressure that one gas in a mixture would exert if it occupied the total volume by itself at a given temperature
85
what is the partial pressure of oxygen in atmospheric air?
760x0.21= 160 mmHg
86
what contributes to about 47mmHg of the total pressure in the lungs?
water vapour pressure
87
How do you calculate the value for the pressure of inspired air?
ii. what is its value at sea level?
Atmospheric pressure- water vapour
ii. 713 mmHg (760-47)
88
What is the alveolar gas equation?
PAO2 = PiO2- [PaCO2/0.8]
89
what does PAO2 mean?
partial pressure of o2 in alveolar air
90
what does PIO2 mean?
partial pressure of O2 in inspired air
91
what does PACO2 mean?
partial pressure of CO2 in arterial blood
92
What is the respiratory exchange ratio?
ii. what is its value?
Ratio of CO2 produced /O2 consumed
ii. 0.8
93
What is the normal value of arterial PCO2?
40 mmHg
94
at a normal arterial PCO2 what is the PAO2?
PAO2 = 150mmHg - [40/0.8]
| =100mHg
95
how do you convert mmHg pressure to kPa?
kPa = mmHg/7.5
96
Across pulmonary capillaries what is the partial pressure gradient value of PAO2?
( from alveoli to blood)
60 mmHg ( 8kP)
| 100-40
97
Across pulmonary capillaries what is the partial pressure gradient value of PCO2?
(from blood to alveoli)
6 mm Hg (0.8 kP)
| 46-40
98
Across systemic capillaries what is the partial pressure gradient value of PaO2?
( blood to tissue cell)
>60 mm Hg
| 100-<40
99
Across systemic capillaries what is the partial pressure gradient of PCo2
(tissue cell to blood)
>6 mmHg
| >46-40
100
why is the partial pressure gradient for CO2 much smaller than O2?
CO2 is more soluble in membranes than O2 due to it having a much higher diffusion coefficient
101
What is the diffusion coeffecient?
Solubility of a gas in membranes
102
what is the difference between PaO2 and PAO2?
PaO2- arterial PO2
PAO2- alveolar PO2
103
what does a large gradient between PAO2 and PaO2 suggest?
Problems with gas exchange in lungs
or
Right to left shunt in the heart
104
What is Fick's law of diffusion?
Amount of gas that moves across a shoot tissue in unit time is proportional to the area of the sheet but indirectly proportional to the thickness of the sheet
105
what does pulmonary circulation recieve?
the entire cardiac output
106
why is a small gradient between PAO2 and PaO2 normal?
ventilation-perfusion match is usually not perfect
107
what is the role of Type 1 alveolar cells?
gas exchange
108
what encircles each alveolus?
pulmonary capillaries
109
Discuss the four main factors' influence on the rate of gas exchange.
1. As Partial pressure gradient increases so does rate of gas exchange
2. As Diffusion coefficient increase so does Gas exchange rate
3. As Surface area increase so does rate of gas exchange.
4. As thickness of membrane increase the gas exchange rate decreases
110
What are the main non-respiratory functions of the respiratory system?
Route for water loss and heat elimination
Enhances venous return
Maintains acid-base balance
Enables speech
Defends inhaled foreign matter
Removes, modifies, activates or inactivates various materials passing through the pulmonary circulation
Nose smells stuff
111
What is Henry's Law?
The amount of a given gas dissolved in a given type and volume of liquid (blood) at a constant temperature is proportional to the partial pressure of the gas in equilibrium with the liquid
therefore: if the partial pressure in the gas phase is increased the concentration of the gas in the liquid phase would increase proportionally.
112
what is the value of cardiac output at resting conditions?
5L/min
113
what is the rate of dissolved o2 which reaches tissues in resting conditions?
15ml/min
114
What is the value of cardiac output at strenuous exercise?
30 L/min
115
What is the rate of dissolved O2 which reaches tissues in strenuous conditions?
90ml/min
116
At resting conditions what is rate of total oxygen consumption in body cells?
250ml/min
117
what are the two main ways in which oxygen is transported?
1. Bound to haemoglobin (98.5%)
| 2. dissolved ( 1.5%)
118
What is the volume of dissolved oxygen in one litre of blood?
3 ml
119
what is the volume of oxygen in one litre of blood?
200 ml
120
How many haem groups are in one Hb molecule?
4 haem groups- oxygen revsibly binds to each one
121
What is the primary factor which determines the percent saturation of haemoglobin with O2?
Po2
122
How many alpha chains are in one Hb molecule?
2
123
How many beta chains are in one Hb molecule?
2
124
When is haemoglobin is considered fully saturated?
when all Hb present is carrying maximum O2 load
125
what is the average resting PO2 at systemic capillaries?
5.3 kPa
126
what is the normal Po2 at pulmonary capillaries?
13.3 kPa
127
How do you calculate the oxygen delivery index?
Oxygen content of arterial blood x Cardiac index= DO2L( ml.min/meter2)
128
what is Cao2?
oxygen content of arterial blood
129
What is the cardiac index?
Cardiac output to the body surface area( size of individual)
130
What is the normal range of cardiac index?
2.4-4.2L/min/meter^2
131
How do you calculate Cao2?
1.34x{Hb}xSaO2
132
what is Sao2?
ii. what is it determined by?
Percentage of haemoglobin with oxygen in arterial blood.
ii. Po2
133
How much oxygen does one gram of Hb carry when fully saturated?
1.34 ml
134
What does the partial pressure of inspired oxygen depend on?
total pressure and proportion of oxygen in gas mixture
135
What factors does the partial pressure of inspired oxygen depends on?
Total pressure ( e.g. atmospheric pressure)
proportion of oxygen in gas mixture (21% in atmosphere)
136
What does the binding of the first O2 molecule to Hb do?
Increases the affinity of Hb for O2
(sigmoid curve)- flattens when all sites are occupied
137
What does the flat upper portion of the sigmoid curve mean?
That a moderate fall in Alveolar Po2 will not affect oxygen loading
138
What does the steep lower part of the sigmoid curve mean?
Peripheral tissues get a lot of oxygen for a small drop in capillary Po2
139
What is the Bohr effect?
when the dissociation curve shifts to the right
increase in CO2 in the blood causes O2 to be displaced from the hemoglobin
140
What factors causes the bohr effect to occur?
Increase in Pco2
increase in [H+]
increase in temperature
Increase in 2,3-biphosphoglycerate
141
Where does Bohr effect occur?
at tissues
142
How does fetal haemoglobin differ from adult haemoglobin?
1. HbF has 2 alpha and 2 gamma (rather than 2 beta) subunits
2. HbF interacts less with 2,3-biphosphoglycerate in erythrocytes
3. HbF has a higher affinity for O2
This means Fetal dissociation curve will be to the left of adult curve ( binds at a lower PO2)
143
What does the positioning of the fetal dissociation curve in comparison of the adult dissociation curve?
Oxygen transfer from mother to foetus can occur even if PO2 is low
144
What is myoglobin?
an iron containing protein which resembles Hb and is found in skeletal and cardiac muscles
145
How many haem groups are in one myoglobin molecule?
one
146
What is the difference between Myoglobin and haemoglobin?
Myoglobin is found in Muscle cells ( Haemoglobin in RBC)
one Haem group in myoglobin ( 4 in haemoglobin)
Dissocaition curve for Mb is hyperbolic (sigmoid for Hb)
Mb releases O2 at much lower Po2
147
What is the role of Myoglobin?
Provides a short-term storage of O2 for anaerobic conditions
148
How is CO2 transported in blood starting from most popular to least?
1. Bicarbonate (60%)
2. Carbamino compounds (30%)
3. solution (10%)
149
What is the formula for bicarbonate formation?
ii. where does it occur
CO2 + H2O (reversible with) H2CO3 (reversible with) H+ + HCO3-
ii. erythrocyte
150
What enzyme catalyses the formation of the bicarbonate?
Carbonic anhydrase
151
When bicarbonate diffuses out of Erythrocyte what occurs after?
chloride shift in order for no build up of electric change takes place during gas exchange
152
what happens to the hydrogen ions that are formed during the bicarbonate reaction?
binds to haemoglobin to form haemoglobinic acid
153
How are carbamino compounds formed?
Combination of Co2 with terminal amine groups in blood proteins
154
What does carbamino compounds bind to?
haemoglobin- to form carbamino-haemoglobin
155
Reduced Hb can bind more Co2 than HBO2 true or false?
true
156
What is the haldane effect?
Removing of O2 from Hb increases the ability of Hb to pick up Co2 and Co2 generated H+
157
What do the Bohr effect and haldane effect allow to occur?
O2 liberation ( bohr shift)
and uptake of CO2 and CO2 generated H+ (Haldane effect)
to occur in tissues
158
what neurones generate the breathing rhythm (act as a pacemaker) for respiration?
pre-botzinger complex in the medullary respiratory centre
159
What does the respiratory control centres in the brain stem consist of?
Pons respiratory centre
Medullary respiratory centre
160
What does the Pons respiratory centre consist of?
Pneumotaxic centre
Apneustic centre
161
What does the Medullary respiratory centre consist of?
Dorsal respiratory group
Ventral respiratory group
162
what causes contraction of inspiratory muscles and therefore causes inspiration?
Rhythm generated by pre Botzinger complex excites the dorsal respiratory group
163
What causes active expiration?
Increased firing of dorsal neurones excites the ventral respiratory group neurones which activate expiratory muscles.
does not occur in quiet breathing!
164
What is the role of the Pneumotaxic centre?
Terminates inspiration when stimulated
165
What stimulates the Pneumotaxic centre?
firing of Dorsal respiratory neurones
166
What is Apneusis?
state in which prolonged inhalation occurs with brief expiration. occurs when Pneumotaxic centre is absent
167
What is the function of the apenustic centre?
prolong inspiration
168
what are the 4 types of involuntary (reflex) modifications of breathing?
1. Hering-Breuer Reflex
2. joint receptors reflex
3. stimulation of respiratory centre
4. cough reflex
169
What is the Hering-breuer reflex?
when the lungs become overly inflated, the pulmonary stretch receptors activate an appropriate feedback response that “switches off” the inspiratory ramp and thus stops further inspiration
170
What are the main factors which increase ventilation during Exercise?
Body movement (joint receptors)
Adrenaline release
Cerebral cortex impulse
Increase in body temperature
accumulation of Co2 and H+ from muscle respiring
171
What happens when ventilation is 0 but perfusion is normal?
V/Q ratio =0
172
what happens when perfusion is zero but ventilation is normal?
V/Q ratio= infinity
173
What is the function of the cough reflex?
help clear airways
174
What is the cough reflex activated by?
irritation of airways
175
where is the centre of cough reflex?
medulla
176
what is the events that occur during a cough reflex?
1. irritation of airways/tight airways
2. afferent discharge
3. short intake of breath
4. closure of larynx
5. contraction of abdominal muscles to increase intra-alveolar pressure
6. opening of the larynx
7. expulsion of air at high speed
177
What type of control system is the chemical control of respiration?
negative feedback
178
What are the control variable of the respiartion?
blood gas tensions- especially co2
179
what is the function of peripheral chemoreceptors?
sense tension of oxygen, co2 and [H+] in the blood
180
Where are peripheral chemoreceptors found?
Carotid bodies
Aortic bodies
181
Where are central chemoreceptors found?
near the surface of the medulla of the brainstem
182
What is the function of central chemoreceptors?
Respond to [H+] of the CSF
183
What separates CSF from blood?
Blood brain barrier
184
what is the blood-brain barrier impermeable to?
H+ and HCo3-
185
what is the Blood brain barrier permeable to?
Co2
186
What is the difference between CSF and blood?
Contains less protein and is less buffered than blood
187
what happens when CO2 diffuses across the blood brain barrier?
dissociated into H+ ions
as there is a low protein content of the CSF the ions produced arent buffered well and so stimulate the central chemoreceptor
188
what is hypercapnia?
presence in the blood of an abnormally high concentration of co2
189
what is hypoxia?
deficiency of oxygen in the tissues
190
as hypercapnia increases slightly what happens to ventilation?
increases rapidly:
| to remove excess CO2
191
what happens to the respiratory centre neurones when there is severe hypoxia?
become depressed and so there is a poor ventilation
192
as a general trend, what happens when PO2 increases?
ventilation decreases
193
as altitude increases what happens to the partial pressure of oxygen?
decreases
194
what are the chemoreceptors which control the hypoxic drive of respiration?
peripheral chemoreceptors
195
What causes hypoxia at high altitudes?
Decreased PiO2
196
What are the acute responses to hypoxia?
Hyperventilation
increased cardiac output
197
What chronic adaptations occur to high altitude hypoxia?
Increased RBC production (polycythaemia)- o2 carrying capacity of blood increased
increased production 2,3-BPG within RBC- O2 offloaded more easily into tissues
increased number of capillaries- blood diffuses more easily
increased number of mitochondria- o2 can be used more efficiently
kidneys conserve acid- arterial pH decrease
198
what causes the H+ drive of respiration?
peripheral chemoreceptors
199
what is the role of H+ drive of respiration?
adjusts for acidosis caused by the addition of non-carbonic acid H+
(eg lactic acid or diabetic ketoacidosis)
200
what does the H+ drive of respiration cause?
hyperventilation and increases elimination of CO2 from the body (reduces body acid content)
201
What are the effects of arterial Pco2 on:
1. peripheral chemoreceptors
2. central chemoreceptors
1. Weak stimulation
| 2. strong stimulation- dominant control of ventilation
202
What are the effects of arterial PO2 on:
1. Peripheral chemoreceptors
2. Central chemoreceptors
1. Only become important if PO2 fall below 8kPa
| 2. Severe hypoxia depresses respiratory centre
203
What are the effects of arterial H+ on:
1. Peripheral chemoreceptors
2. central chemoreceptors
1. stimulation - important for acid -base balance
| 2. H+ cannot cross BBB
204
What is the function of the pleural fluid?
Lubrication
| Provides surface tension
205
what is normal expiration?
Is a passive process, controlled by the gaps in firing of dorsal neurons within the medulla
206
what is forced expiration?
Is an active process, controlled by the firing of ventral neurons in the medulla
207
what is normal inspiration?
Is an active process, controlled by the firing of dorsal neurons within the medulla
