Physiology Flashcards
(204 cards)
0
Q
What is external respiration?
A
the sequence of events that leads to the exchange of oxygen and carbon dioxide between the external environment and the cells of the body.
1
Q
What does internal respiration refer to?
A
The intracellular mechanisms which consume oxygen and produce carbon dioxide.
2
Q
Name the four steps of external respiration
A
Ventilation, gas exchange between alveoli and blood, gas transport in the blood, gas exchange at tissue level
3
Q
State Boyle’s law
A
At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas. As the volume of a gas increases, the pressure exerted by the gas decreases.
4
Q
What are the two forces that hold the thoracic wall and the lungs in close opposition?
A
- intrapleural fluid cohesiveness: the water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart. Hence the pleural membranes tend to stick together.
- negative intrapleural pressure: the sub-atmospheric intrapleural pressure creates a transmural pressure gradient across the lung wall and across the chest wall. So the lungs are forced to expand outwards while the chest is forced to squeeze inwards.
5
Q
What are the typical values of: atmospheric pressure, intra alveolar pressure and intrapleural pressure?
A
760, 760, 755
6
Q
What is a pneumothorax?
A
Air in the pleural space
7
Q
What causes lungs to recoil during expiration?
A
Elastic connective tissue and alveolar surface tension
8
Q
Explain the law of LaPlace in relation to small alveoli
A
the smaller alveoli have a higher tendency to collapse
9
Q
What is pulmonary surfactant?
A
A complex mixture of lipids and proteins secreted by type II alveoli. It lowers alveolar surface tension.
10
Q
What is alveolar interdependence?
A
if an alveolus starts to collapse the surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus to open it.
11
Q
Name the accessory muscles of inspiration, the major muscles and the muscles of active expiration.
A
Scalenus and sternocleidomasteod, extenal intercostal muscles and diaphragm, abdominal muscles
12
Q
Tidal volume volume
A
500ml
13
Q
Inspiratory reserve volume volume
A
3000ml
14
Q
Inspiratory capacity volume
A
3500ml
15
Q
expiratory reserve volume volume
A
1000ml
16
Q
residual volume volume
A
1200ml
17
Q
functional residual capacity volume
A
2200ml
18
Q
vital capacity volume
A
4500ml
19
Q
total lung capacity volume
A
5700ml
20
Q
What is the tidal volume?
A
The volume of air entering and leaving the lungs during a single breath
21
Q
What is the inspiratory reserve volume?
A
The extra volume of air that can be maximally inspired over and above the typical resting tidal volume
22
Q
What is the inspiratory capacity?
A
The maximum volume of air that can be inspired at the end of a normal quiet expiration. IC = TV + IRV
23
Q
What is the expiratory reserve volume?
A
The extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume.
24
What is the residual volume?
The minimum volume of air remaining in the lungs even after maximal expiration.
25
What is functional residual capacity?
The volume of air in the lungs at the end of normal passive expiration (FRC = ERV + RV)
26
What is the vital capacity?
The maximum volume of air that can be moved out during a single breath following a maximal inspiration (VC = IRV + TV + ERV)
27
What is total lung capacity?
The maximum volume of air that the lungs can hold (TLC = VC + RV)
28
What is forced expiratory volume in one second (FEV1) ?
Th volume of air that can be expired during the first second of expiration in an FVC determination. A ration with a percentage above 75% is normal.
29
What does parasympathetic stimulation do to the bronchioles?
Causes bronchoconstriction
30
What does sympathetic stimulation do to the bronchioles?
Causes bronchodilatation
31
What is pulmonary compliance?
The measure of effort that has to go into stretching or distnding the lungs
32
Name five factors that decrease pulmonary compliance
pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant
33
In what condition does increased compliance occur?
emphysema
34
What is anatomical dead space?
Inspired air that remains in the airways and is not available for gas exchange (150ml)
35
What is pulmonary ventilation?
The volume of air breathed in and out per minute. TV + RR = 0.5 + 12 = 6 L/min
36
Why is alveolar ventilation less than pulmonary ventilation?
Because of the presence of anatomical dead space
37
What is alveolar ventilation?
The volume of air exchanged between the atmosphere and alveoli per minute. It represents the new air available for gas exchange with blood. (TV - dead space) x RR = (0.5 - 0.15) x 12 = 4.2 L/min
38
What does decreased oxygen do to pulmonary arterioles?
Vasoconstriction
39
What does increased oxygen do to pulmonary arterioles?
Vasodilatation
40
What does decreased oxygen do to systemic arterioles?
Vasodilatation
41
What does increased oxygen do to systemic arterioles?
Vasoconstriction
42
State Dalton's law
the total pressure exerted by a gaseous mixture depends on the sum of the partisl pressures of each individual component in the gas mixture
43
How much does watere vapour pressure contribute to the total pressure in the lungs?
47 mmHg
44
What is the pressure of inspired air and how was it worked out?
atmospheric pressure - water vapour pressure = 760 - 47 = 713 mm Hg
45
What is the partial pressure of oxygen?
150 mmHg
46
Across pulmonary capillaries: what is the partial pressure gradient of oxygen from alveoli to blood?
60 mmHg
47
Across the pulmonary capillaries: what is the partial pressure gradient of carbon dioxide from blood to alveoli?
6 mmHg
48
Across systemic capillaries: what is the partial pressure gradient of oxygen from blood to tissue cell?
greater than 60 mmHg
49
Across systemic capillaries what is the partial pressure gradient of carbon dioxide from tissue cell to blood ?
greater than 6 mmHg
50
Which is more soluble in membranes - CO2 or oxygen?
CO2
51
What is the solubility of gas in membranes known as?
The diffusion coefficient.
52
How much greater is the diffusion coefficient for C02 compared to oxygen?
20 times greater
53
What would a big gradient between PA02 and Pa02 indicate?
Problems with gas exchange in the lungs or a right to left shunt in the heart
54
How much of the cardiac output does the pulmonary circulation receive?
The entire cardiac output
55
What has a respiratory membrane?
Alveoli
56
What do the walls of alveoli consist of?
Single layer of flattened type I alveolar cells
57
What encricles each alveolus?
Pulmonary capillaries
58
Name 4 factors that influence the rate of gas exchange across alveolar membranes?
1. Partial pressure gradients of O2 and CO2
2. Surface area of alveolar membrane
3. Thickness of blood/air barrier across membrane
4. Diffusion coefficient (solubility of gas in membrane)
59
In relation to the partial pressure gradients of O2 and CO2: what happens when the partial pressure increases?
Rate of transfer of gas exchange across alveolar membranes increases
60
In relation to hte surface area of alveolar membranes: what occurs when the surface area increases?
Rate of transfer increases
61
What does the surface area of alveolar membranes increase during and why?
During exercise as more pulmonary capillaries open up when the cardiac output increases and the alveoli expand as breathing deepens
62
In relation to the thickness of blood/air barrier across membranes: what occurs as it thickens?
Rate of transfer decreases
63
What does thickness of blood/air barrier across membrane increase with?
Pathological conditions such as pulmonary oedma, pulmonary fibrosis and pneumonia
64
In relation to the diffusion coefficient (solubility of gas in membrane): what occurs as the diffusion coefficient decreases?
Rate of transfer increases
65
Where must oxygen that has been picked up by the blood be transported to?
Tissues for cellular use
66
Where must CO2 produced at the tissues be transported to?
The lungs for removal from the body
67
What is the PO2 in atmospheric air?
160
68
What is the PCO2 in atmospheric air?
0.03
69
What is the PO2 in alveoli?
100
70
What is the PCO2 in alveoli?
40
71
What is the PO2 in deoxygenated blood?
40
72
What is the PCO2 in deoxygenated blood?
46
73
What is the PO2 in oxygenated blood?
100
74
What is the PCO2 in oxygenated blood?
40
75
In the tissues what is the PO2?
<40
76
In the tissues what is the PCO2?
>46
77
What law relates to the effect of partial pressure on gas solubility?
Henry's law
78
What is Henry's law?
The amount of a given gas dissolve in a given type and volume of liquid (e.g. blood)v at a constant temperature is: proportional to the partial pressure of the gas in equilibrium with the liquid.
79
If the partial pressure in the gas phase is increased, what happens to the concentration of the gas in the liquid phase?
It would increase proportionally
80
What is the oxygen amount dissolved in blood proportional to?
The partial pressure
81
How much oxygen is there per litre of blood at P02 of 13.3kPa?
3ml
82
Under resting conditions - what is cardiac output?
5L/min
83
Under resting conditions how much oxygen per minute is taken to tissues as dissolved O2?
15ml/min
84
What is the cardiac output during strenuous exercise?
30L/min
85
During srenuous exercise much much oxygen per minute would be taken to tissues as dissolved oxygen?
90ml/min
86
What is the resting oxygen consumption of our body cells?
About 250ml/min
87
How much may oxygen consumption increase during strenuous exericese?
25 folds
88
How is most oxygen in the blood transported?
Bound to haemoglobin
89
What is the normal oxygen concentration in the arterial blood at a normal arterial PO2 of 13.3kPa?
20ml/100ml (200ml per litre)
90
What is the normal haemoglobin concentration at a normal arterial PO2 of 13.3kPa?
15g/100ml
91
What is the percentage of oxygen carried bound to haemoglobin?
98.5%
92
What is the percentage of oxygen carried in the dissolved form?
1.5% (3ml per litre at a PO2 of 13.3kPa
93
What two forms is oxygen present in the blood in?
Bound to haemoglobin or physically dissolved
94
What kind of combination does haemoglobin form with oxygen?
Reversible
95
How many haem groups does a Hb molcule contain?
4 haem groups
96
When is haemoglobin considered fully saturated?
When all the Hb present is carrying its maximum oxygen load
97
What is the primary factor which determines the percent saturation of haemoglobin with oxygen?
PO2
98
What is the equation for the oxygen delivery index? (DO2I)
DO2I = CaO2 x Cl
99
What is CaO2?
Oxygen content of arterial blood (ml/L)
100
What is CI?
Cardiac index (L/min/metre)
101
What does the cardiac index relate to?
The cardiac output to the body surface area (i.e. size of the individual)
102
What is the normal range for CL?
2.4 - 4.2 L/min/metre
103
What is the oxygen delivery to the tissues a function of?
Oxygen content of arterial blood and the cardiac output
104
What is the equation for the oxygen content of arterial blood (CaO2)?
CaO2 = 1.34 x [Hb] x SaO2
105
How much oxygen does 1 gram of Hb carry when fully saturated?
1.34ml
106
In the oxygen content of arterial blood (CaO2) equation: what is [Hb] and SaO2?
```
[Hb] = haemoglobin concentration (gram/L)
SaO2 = %Hb saturated with O2 (remember this is determined by PO2)
```
107
What is the oxygen content of arterial blood determined by?
Haemoglobin concentration [Hb] and the saturation of Hb with O2
108
What three things can impair oxygen delivery to the tissues?
Respiratory disease
Heart failure
Anaemia
109
What does the binding of one oxygen to Hb increase?
The affinity of Hb for oxygen
110
What happens to haemoglobin where all the sites are becoming occupied?
Flattens
111
What is co-operativity in relation to oxygen binding to haemoglobin?
Binding of one oxygen to Hb increaeses the affinity of Hb for oxygen
112
What are heme group, beta chains and alpha chains all a part of?
Haemoglobin
113
On a graph where the y axis is %haemoglobin saturation, x axis is blood PO2 (kPa) and the right axis is O2 concentration ml/100ml: What does the flat upper portions of a sigmoid curve mean?
Means that moderate fall in alveolar PO2 will not much affect oxygen loading.
114
On a graph where the y axis is %haemoglobin saturation, x axis is blood PO2 (kPa) and the right axis is O2 concentration ml/100ml: What does the steep lower part of the sigmoid curve mean?
That the peripheral tissues get a lot of oxygen for a small drop in capillary PO2
115
What is the Bohr effect - on a graph with y axis as % Hb saturation and x axis of PO2?
A shift of the curve to the right: The Bohr effect
116
What 4 things increase to give the Bohr effect?
1. PCO2
2. [H+]
3. Temperature
4. 2,3-Bisphosphoglycerate
117
The Bohr effect is a shift of the curve to the right, what does this mean?
Increased release of oxygen by conditions at the tissues
118
What type of tension has 100 PO2 and 13.3kP?
Arterial O2 tension
119
What type of tension has PO2 of 40 and 5.3kP?
Tissue oxygen tension
120
On a graph with O2 content as the y-axis and PO2 (mm Hg, kP) as the x-axis: which curve is more left and finishes higher - curve in arterial conditions or curve in tissue conditions?
Curve in arterial conditions
121
Where is myoglobin present?
In skeletal and cardiac muscles
122
How many haem groups per myoglobin molecule?
one
123
In relation to myoglobin is htere any cooperative binding of oxygen?
No
124
On a graph with % saturation of myoglobin on y-axis and PO2 mmHg on x-axis, what is the curve like?
Dissociation curve hyperbolic
125
At what level of PO2 does myoglobin release oxygen?
At very low PO2
126
On a graph with %saturation on y-axis and PO2 mmHg on x-axis: which curve is more left - dissociation curve for myoglobin (1:1 binding) or dissociation curve for haemoglobin?
Dissociation curve for myoglobin (1:1 binding)
127
What does myoglobin provide a short term storage of oxygen for?
Anaerobic conditions
128
What does the presence of myglobin the the blood indicate?
Muscle damage
129
Describe the 3 means of CO2 transport in the blood (including %)
1. Solution (10%)
2. As Bicarbonate (60%)
3. As Carbamino compounds (30%)
130
What law is associated with CO2 transportation in solution?
Henry's law
131
How is most CO2 transported in the blood?
As bicarbonate
132
What is the equation for Bicarbonate being formed in the blood?
CO2 + H20 = H2CO3 = H+ + HCO3
133
Where does carbonic anhydrase occur?
In red blood cells
134
How are carbamino compounds formed?
By the combination of CO2 with terminal amine groups in blood proteins
135
What gives carbamino-haemoglobin?
Globin of haemoglobin and CO2
136
Can reduced Hb bind more CO2 than HbO2?
Yes
137
What is the haldane effect?
Removing oxygen from Hb increases the ability of Hb to pick-up CO2 and CO2 generated H+
138
What does the Haldane effect work in synchrony with?
The Boher effect
139
What to effects work in synchrony to facilitate oxygen liberation and uptake of CO2 and CO2 generated H+ at tissues?
Boher effect and Haldane effect
140
What is haemoglobin present in the red blood cells as?
Carbonic anhydrase
141
What is the enzyme that caralyses the production of bicarbonate?
Carbonic anhydrase
142
What does the H+ generated during the production of HCO3 bind to?
Hb
143
How does bicarbonate move out of red blood cells and into the plasma?
By facilitated diffusion down its concentration gradient
144
Name the 4 sections of the sagital brain stem from inner most to outer?
1. Midpoint
2. Pons
3. Medulla oblongata
4. Spinal cord
145
What part of the brain stem is the major rythm generator?
Medulla
146
What network of neurons generate the breathing rhythm?
Pre-Botzinger complex
147
What kind of activity do Pre-Botzinger complex neurons display?
Pacemaker actiivty
148
Where are the Pre-Botzinger complex neurons located?
Near the upper end of the medullary respiratory centre
149
In the pons of the brainstem - what two centers are present?
Pneumotaxic center and apneustic center
150
What respiratory group is the Pre-Botzinger complex above?
The ventral respiratory group
151
Which respiratory group is posterior to the ventral respiratory group in the brain stem?
Dorsal respiratory group
152
What two respiratory groups are in the medullary respiratory center?
Dorsal respiratory group
| Ventral respiratory group
153
What group of neurones in the brainstem give rise to inspiration?
The dorsal respiratory group neurones
154
How do the dorsal respiratory group neurones fire?
In bursts
155
What does firing of the dorsal respiratory group neurones lead to?
Contraction of inspiratory muscles - inspiration
156
When firing of the dorsal respiratory group neurones stop - what happens?
Passive expiration
157
During 'active' expiration during hyperventilation - what happens when there is increased firing of dorsal neruones?
They excite a second group called the ventral respiratory group neurones
158
What do the ventral respiratory group neurones excite and what doesthis cause?
Excite internal intercostals, abdominals which leads to forceful expiration
159
In normal quiet breathing, dp ventral neurones activate expiratory muscles?
No
160
The rhythm generated in the medulla can be modified by what neurones?
In the pons
161
What does stimulation of the pneumotaxic centre (PC) terminate?
Inspiration
162
When is the pneumotaxic centre (PC) stimulated?
When the dorsal respiratory neurones fire
163
When the PC is stimulated when dorsal respiratory neurones fire - what is inhibited?
Inspiration
164
Without PC, breathing is prolonged inspiratory gasps with brief expiration - what is the name for this?
Apneusis
165
What do impulses from the apneustic centre excite?
Inspiratory area of the medulla
166
When the apneustic centre inpulses excite the respiratory area of the medulla what occurs?
Prolonged inspiration
167
Where is the rythm generated and where can it be modified?
Generated in medulla and modified by inputs from pons
168
Respiratory centres are influenced by stimuli received from what 7 receptors?
1. Higher brain centres
2. Stretch receptors
3. Juxtapulmonary receptors
4. Joint receptors
5. Baroreceptors
6. Central cehmoreceptors
7. Peripheral chemoreceptors
169
What are the 3 higher brain centres?
Cerebral cortex, limbic system, hypothalamus
170
Where are stretch receptors located?
In the walls of the bronchi and bronchioles
171
What does the inflation Hering-Breur reflex guard against?
Hyperinflation
172
What 3 things stimulate the J receptors?
Pulmonary capillary congestion and pulmonary oedema, also pulmonary emboli
173
What heart failure causes pulmonary oedema?
Left sided
174
How are joint receptors stimulated?
Joint movement
175
In relation to baroreceptors what causes increased ventilatory rate?
Decreased blood pressure
176
Give 4 examples of involuntary modifications of breathing
1. Pulmonary stretch receptors Hering-Breuer Reflex
2. Joint receptors reflex in exercise
3. Stimulation of respiratory centre by temperature, adrenaline, or impulses from cerebral cortex
4. Cough refelx
177
When are pulmonary stretch receptors activated and what do the afferent discharges inhibit?
Activated during inspiration, afferent discharge inhibits inspiration - Hering-Breur reflex
178
At what level of tidal volumes are pulmonary stretch receptors activated?
At large >> 1 litre tidal volumes
179
What do impulses from moving limbs increase?
Breathing
180
What 5 factors may increase ventilation during exercise?
1. Reflexes originating from body movement
2. Adrenaline release
3. Impulses from the cerebral cortex
4. Increase in body temperature
5. Later: accumulation of CO2 and H+ generated by active muscles
181
Where is the cough reflex control centre?
Centre in the medulla
182
In relation to the cough reflex: what does afferent discharge stimulate?
Short intake of breath, followed by closeure of the larynx, then contraction of abdominal muscles (increases intra-alveolar pressure), and finally opening of the larynx and expulsin of air at a high speed
183
What kind of feedback is chemical control of respiration an example pof?
Negative feedback
184
In the chemical control of respiration: what are the controlled variables?
Blood gas tensions, especially carbon dioxide
185
What do chemoreceptors sense the values of?
Gas tensions
186
Where are the two peripheral chemoreceptors located?
Carotid bodies and aortic bodies
187
What 3 things do the peripheral chemoreceptors sense?
Tension of oxygen, carbon dioxide and [H+] in the blood
188
Where are the central chemoreceptors situated?
Near the surface of the medulla of the brainstem
189
What do the central chemoreceptors respond to?
[H+] of the cerebrospinal fluid (CSF)
190
What seperates the CSF from the blood?
The blood/brain barrier
191
What is the blood-brain barrier relatively impermeable to and whayt diffuses readily across it?
Relatively impermeable to H+ and HCO3
| CO2 diffuses readily
192
Is CSF less buffered that blood?
Yes - contains less protein
193
What is ventilation very responsive to?
PCO2
194
In relation to the hypoxic drive of respiration: what is the effect via?
Peripheral chemoreceptors
195
When is the hypoxic drive of respiration stimulated?
When arterial PO2 falls to low levels (<8.0 kPa)
196
When may hypoxic drive of respiration become important?
In patients with chronic CO2 retention (patients with COPD)
| At high altitudes
197
What is hypoxia at high altitudes caused by?
Decreased partial pressure of inspired oxygen (PiO2)
198
What are the 2 acute responses of jhypoxia at high altitudes?
Hyperventilation
| Increased cardiac output
199
What are the 5 chronic adaptions to high altitude hypoxia?
1. Increased red blood cell production (polycythaemia) - O2 carrying capacity of blood increases
2. 2,3 BPG produced within RBC - O2 offloaded more easily into tissues
3. Increased number of capillaries - blood diffuses more easily
4. Increased number of mitochondria - O2 can be used more efficiently
5. Kidneys conserve acid - arteiral pH decreases
200
What is the effect of the H+ drive of respiration?
Via the peripheral chemoreceptors
201
Does H+ readily cross the blood brain barrier?
No (CO2 does)
202
The peripheral chemoreceptors play a major role in adjusting for acidosis. What is the acidosis caused by?
The addition of non-carbonic acid H+ to the blood (e.g. lactic acid during exercise; and diabetic ketoacidosis)
203
What does peripheral chemoreceptor stimulation by H+ cause?
Hyperventilation and increases elimination of CO2 from the body
(important in acid-base balance)
Remember CO2 can generate H+, so its increased elimination help reduce the load of H+ in the body)
