Respiratory physiology Flashcards
(172 cards)
1
Q
What are the functions of the respiratory system ?
A
- Gas exchange
- Acid base balance
- Protection from infection
- Communication via speech
2
Q
Which two mechanisms does gas exchange reply most heavily on ?
A
Inhalation and exhalation
3
Q
What is meant by a ‘ steady state of volume ‘?
A
Volume of gas exchange at the lungs matches the volume of gas exchange at the tissues
4
Q
Why is a steady state of volume important?
A
Ensures that supply equals demand and there isn’t a build up of gas in the circulation
5
Q
What is Acid-base balance ?
A
The regulation of the ECF pH. It is controlled by the repiratory and renal systems working together.
6
Q
Very broadly, what are the two ways in which the reparatory system can be classified ?
A
- External and internal respiration
- Pulmonary and systemic
7
Q
Describe the external and internal respiration
A
The external - Getting oxygen in and carbon dioxide out and around the body.
The internal - Use of oxygen and production of Carbon dioxide in cellular reactions
8
Q
Describe pulmonary and systemic circulation
A
Pulmonary - heart to lungs and back. Arteries have de-oxygenated blood while veins have oxygenated blood.
Systemic - Heart to tissues and back. Arties have oxygenated blood while veins have de-oxygenated blood.
9
Q
Name the 8 terminologies used to describe breathing
A
Tidal volume Residual volume Expiratory reserve volume Inspiratory reserve volume Total lung capacity Inspiratory capacity Vital capacity Functional residual capacity
10
Q
What is the tidal volume ?
A
500ml which is expired and then inspired in a normal breath at rest
11
Q
What is residual volume?
A
1200ml of air which is always found within the lungs and you cant remove.
12
Q
What is the function of the residual volume ?
A
- Prevents alveoli from collapsing which means that they require less energy to fill with air.
- Allows gas exchange to continue continually (i.e. even while not actively inspiring)
13
Q
What is the expiratory reserve volume ?
A
The volume of air which you can voluntarily expire but don’t breath out in a normally expiration at rest
14
Q
What is the inspiratory reserve volume ?
A
The volume of air which you can voluntarily inhale but don’t breath out in a normally inhale at rest
15
Q
What is the total lung capacity ?
A
The total amount of air which a person can hold in there lungs. In an adult this is normally 6l
16
Q
What is inspiratory capacity ?
A
The volume of air which you can voluntarily inhale including the volume you normally inhale at rest
17
Q
What is vital capacity ?
A
The volume or air in our lungs that we have control over i.e. the total volume we can breath in from when out lungs feel empty or the total volume we can breath out when out lungs are full.
18
Q
What is vital capacity used for?
A
The vital capacity is used to measure lung function
19
Q
What is the functional residual capacity ?
A
The volume of air left in your lungs at the end of a normal exhalation at rest
20
Q
When thinking about the terminology of breathing what is a capacity ?
A
Number of volumes added together
21
Q
What is the normal number of breaths per minuite ?
A
12-18 at rest
40-45 in exercise
22
Q
What are the recall points for ‘the respiratory system’
A
Functions
Classifications
Terminology of breathing
23
Q
Draw diagram of the different terminologies of breathing
A
-
24
Q
What part of the respiratory tract make up the upper respiratory tract ?
A
Nose
Pharynx
Epiglottis
Larynx
25
What is the role of the nose in the respiratory system ?
Allows air to enter the body.
| Contains cilia and mucus which trap particles and warm and moisten the air.
26
Why doesn't air just enter through the mouth ?
Less surface area and therefore it more uncomfortable
27
What is the role of the pharynx in the respiratory system ?
It is the throat and is shared with the digestive system
28
What is the role of the Epiglottis in the respiratory system ?
Where the pharynx becomes the larynx there is a small flat of tissue that folds over the trachea. Normally it is open to allow air into the lower respiratory tract but when we swallow it closed to prevent food from entering it (aspirating).
29
What parts of the respiratory system are considered to be part of the lower respiratory tract?
Trachea
Bronchi
Lungs
30
Describe the path of air though the airways
```
Trachea
Primary bronchi
Secondary bronchi
Tertiary bronchi
Bronchioles
Alveoli
```
31
Describe the trachea
The largest airway is the trachea. It is a semi-rigid tube (patent) whose shape is maintained by C shaped rings of cartilage.
32
Describe the bronchi
The trachea splits into two primary bronchi one for each lung. The right primary bronchi is wider and more vertical than the left primary bronchi. Therefore aspirated foreign bodies are more likely to get stuck in the left bronchi.
The primary bronchi then split into secondary bronchi (one secondary bronchi for each lobe of the lung) and then split into tertiary bronchi (one for each bronchopulmonary segment of the lung). The amount of cartilage decreases the further into the lung you go until there is no cartilage at all. Then these airways are held open by physical forces in the thorax.
Tertiary bronchi then divide multiple times to from bronchioles which divide multiple times forming alveoli.
33
Where does gas exchange occur?
Gas exchange occurs in the alveoli and some bronchioles called respiratory bronchioles. Gas exchange is able to occur here due to a large thin surface.
34
Describe resistance in the airways
In the large airways there is a high level of resistance to air flow while in the small vessels there is a low level of air flow resistance. This is the case because the cumulative diameter of all the little vessels is higher than the diameter of the large vessels and so air flow more easily in the small vessels with larger diameter. Imagine a series of roads, sometimes the biggest are the once's with most traffic and slowest moving cars. Contraction of the bronchial smooth muscle can also increase the airway resistance by decreasing the airway diameter.
35
Describe the basic structure of the right lung
The right lung has three lobes (Superior, middle and inferior) which are separated by a horizontal and then oblique fissure.
36
Describe the basic structure of the left lung
The left lung is slightly smaller because of the positioning of the heart. It has two lobes (superior and inferior) which is separated by an oblique fissure.
37
What volume of fluid is found in each pleural cavity ?
3ml
38
What is the process by which the fluid in the pleural cavity is produced?
Filtration
39
What cells can be found in the pleura ?
Macrophages, lymphocytes and mesothelial cells
40
What is the role of the fluid found in the pleural cavities
Acts like a glue keeping the two sides of the pleura together. It prevents the lungs from separating from the ribcage and diaphragm (the lungs will follow the movements of the ribcage and diaphragm, if the ribs expand so will the lungs and it prevents the recoil of the lungs when they are stretched). At the end of a normal expiration an equilibrium is reached between the lungs which want to recoil a bit and the chest wall that wants to expand a bit. Both are prevented from doing so by the cohesive force of the pleural fluid.
41
What components make up alveoli ? Give a brief statement about there function
Macrophages - Increase lung immune function
Type I pneumocyte - Allow for gas exchange
Type II pneumocyte - Secrete surfactant
Blood vessels - Always surrounded by type I pneumocytes
Elastic fibres - Surround type I pneumocytes allowing for lung expansion
42
What are the two types of pleuritic pleura
In fact just one pleura but two sides;
Visceral (next to the lung)
Parietal (next to the chest wall)
43
Recall points for 'anatomy of the respiratory system'
Parts
Airways
Lungs
Alveoli
44
What are the names of the four laws which govern the mechanics of breathing?
Boyle's law
Dalton's law
Charles Law
Henry's law
45
What does Boyle's law state?
The pressure exerted by a gas is inversely proportional to its volume
46
What does Dalton's law state?
The total pressure of a gas mixture is the sum of the pressures of the individual gases
47
What does Charles Law state?
The volume occupied by a gas is directly related to the absolute temperature.
48
What does Henry's law state?
The amount of gas dissolved in a liquid is determined by the pressure of the gas and its solubility in the liquid.
49
Using your knowledge of the laws of pressure how does breathing work?
Inspiration - Check wall expands, lungs expand, volume increases and so pressure decreases, air moves down its pressure gradient into the lungs
Expiration - the opposite
50
Which muscles are involved in inspiration?
External intercostal muscles
Diaphragm
and occasionally the sternocleidomastoid and scaenas muscles
51
What movement is caused by the muscles of inspiration?
Upward and outward movement of the ribcage
52
What muscles are involved in expiration?
Normally passive but can involve the internal intercostal and abdominal muscles.
53
Describe what happens to the diaphragm through respiration
Diaphragm contacts and flattens to increase volume. It is innervated by the phrenic nerve which causes a contract when it fires.
54
Describe the resistance of the airways during the breathing cycle?
Airways are forced open during inspiration by physical forces.
Airways are compressed by physical forces on expiration.
Therefore resistance is greatest on expiration. This isn't noticed by most people but can aggravate asthma.
55
What are the three different pressure associated with the lungs ?
Intro-thoracic pressure
Intro-pleural pressure
Transpulmonary pressure
56
What is intro-thoracic pressure?
Pressure of the thoracic cavity. If the pressure is greater than atmospheric pressure when it is positive. This is what gives rise to inspiration and expiration and will vary throughout the breathing cycle.
57
What is intro-pleural pressure?
Pressure within the inside of the pleural cavity. In healthy lungs this is always negative. Due to the tension of the chest wall and lungs there is an increase in volume and decrease in pressure the less air that is found in the lungs.
58
What is transpulmonary pressure?
Alveolar pressure - Intra-pleural pressure
| Almost always positive
59
What is surfactant?
It is a detergent like fluid which is produced by type II pneumocytes.
60
What are the functions of surfactant?
- Reduces surface tension
- Helps to prevent alveoli from collapsing
- increases lung compliance
- Reduces the lungs tendency to recoil
61
How does surfactant prevent alveolar collapse?
Water forms a film on the surface of the alveoli. This creates an air water interface. The water molecules are attracted to each other creating an inward directed force which would result in the collapse of the alveoli.
Surfactant sits in between the water molecules and prevents this attraction from forming.
62
Which law does surfactant follow?
The law of LaPlace where P = 2 T/r
63
Is surfactant more effective in large or small alveoli?
Small because of the higher concentration
64
What is IRDS?
Infant respiratory distress syndrome.
Surfactant is complete at week 36. Babies born before that can have IRDS where there alveoli keep collapsing and so breathing requires much more energy.
Breathing air is already harder than amniotic fluid never mind having to inflate collapsed alveoli.
65
What is compliance?
Change in volume relative to the change in pressure. It does not tell anything about the stretch ability of the lungs (I.e. its recoil)
66
What does a highly compliant lung mean ?
A small increase in oxygen causes a large increase in volume
67
What happens to compliance as the pressure and volume increase
it increase
68
Why doesn't the inspiration and expiration graph (of pressure against volume) interpose themselves ?
Because a higher pressure change is require to increase volume at low pressures and a greater decrease in pressure occurs per volume measure at the start of the expiration.
69
What is it called when the initial expansion of the lungs is harder?
Inerita
70
What is ventilation ?
The movement of air into and out of the lungs.
71
What is pulmonary or minute ventilation ?
Total movement or air in and out of the lungs.
72
What is alveolar ventilation?
The volume of fresh air getting into the alveoli
73
What is the normal pulmonary ventilation volume ?
500ml
74
What is the normal alveolar ventilation volume ?
350 ml (500 - 150 of dead space)
75
What is the most effective method of breathing?
Deep and fast
76
What is the difference between hyperventilation and hypoventilation?
```
Hypoventilation = decrease in alveolar ventilation
Hyperventilation = Increase in alveolar ventilation
```
77
What is a partial pressure?
The pressure of a gas in a mixture of gases which is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture.
78
What is the partial pressure of oxygen when the atmospheric pressure is 760mmHg and 21% of the air we breath is O2
21% x760 =160mmHg
79
The actual partial pressure of O2 in the alveoli is only 100mmHg which is this less than 160mmHg?
because the air has been diluted with the dead space
80
What are the normal partial pressures for O2 and CO2 in the alveoli and blood?
Oxygen = 100
| Cardon dioxide = 40
81
In hyperventilation what does the partial pressures for O2 and CO2 change too ?
```
O2 = 120
CO2 = 20
```
82
In hypoventilation what does the partial pressures for O2 and CO2 change too ?
```
O2 = 30
CO2 = 100
```
83
Describe the variation within different parts of lungs to change in volume?
The change in volume is much greater at the base of the lungs. There is greater compliance and ventilation at the base of the lungs. This is because alveoli at the bottom are most compressed and have the most capacity of expand.
84
What is the function of the systemic ciruclation which supplies the lungs?
Provides oxygen, nutrients, hormones, and removes waste.
85
What is the systemic ciruclation of the lungs called?
Bronchial ciruclation
86
What is the rate of gas diffusion dependant on?
- Directly proportional to the partial pressure of the gas.
- Directly proportional to the solubility of the gas.
- Directly proportional to the available surface area.
- Inversely proportional to the thickness of the membrane
87
What does diffusion depending directly on the solubility of the gas mean for respiration?
CO2 is more soluble and so is more easily exchanged across a membrane. This means that although the pressure gradient is not massive it can diffuse very quickly.
88
What does diffusion depending directly on the partial pressure gradient of the gas mean for respiration?
The partial pressure of oxygen is much greater than the partial pressure of CO2 and so it will have a greater gradient and therefore have a greater rate of diffusion.
89
What is the normal diffusion rate for O2
250ml/min
90
What is the normal diffusion rate for CO2
200ml/min
91
What is an obstructive lung condition ?
Hard to exhale all the air in the lungs. There is obstruction to air flow especially on expiration.
92
What is a restrictive lung condition ?
Difficulty in fully expanding lungs for example if there was a loss of compliance.
93
How is lung function measured?
Using the vital capacity i.e. spirometry
94
What is a static lung function test ?
Looks only at exhaled volume
95
What can spirometry be used to measure ?
```
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Inspiratory capacity
Vital capacity
```
96
What is fibrous lung disease?
Fibrous tissue is laid down along side the elastic tissue and this reduces expansion and compliance and the increases the thickness through which gas must diffuse. This results in reduced partial pressure of oxygen in the oxygenated blood.
97
Is fibrous lung disease restrictive or obstructive?
Restrictive
98
What is emphysema ?
Destruction in surface area and therefore a decrease in gas exchange. The loss of surface area means there is a loss of elastic fibres and therefore a loss of ability to move air out of the lungs.
99
Is emphysema obstructive or restrictive ?
Obstructive
100
What is pulmonary oedema ?
Fluid builds up between capillaries and alveoli reducing gas exchange. The water takes up space and prevents effective expansion of the lungs.
101
Is pulmonary oedema obstructive or restrictive ?
Restrictive
102
What is Asthma?
Increased airway resistance
103
Is asthma obstructive or restrictive ?
Obstructive
104
What are the four conditions that you need to know in pathology of gas exchange?
Asthma
Pulmonary Oedema
Emphysema
Fibrosis lung disease
105
What is FEV1/FVC
FEV1 is the forced expiratory volume in 1 second (The volume of air you can push out in the first second). In a healthy person this is about 4.0l. FVC is the forces vital capacity (The volume of air that you can push out in the whole expiration). In a healthy person this is 5.0l.
106
What is the normal valve for FEV1 and FVC and the FEV1/FVC ratio?
```
FEV1= 4l
FVC = 5l
FEV1/FVC = 80%
```
107
What happen to the FEV1/FVC in an obstructive lung disease?
Seriously reduced FEV1 and % and reduced FVC
108
What happen to the FEV1/FVC in an restrictive lung disease?
Reduced FVC and FEV1 and increased %
109
Draw the diagram of normal, obstructive and restrictive lung disease FEV1/FVC
-
110
What is PFER
Peak flow expiratory rate can also be used to measure lung function. Where the rate or expired air is plotted against time allowing abnormalities to be seen if the peak rate lies out with a standard region.
111
Draw what happens to the compliance graph in a obstructive lung disease
-
112
Draw what happens to the compliance graph in a restrictive lung disease
-
113
Recall points for pathology of respiration
Restrictive and obstructive lung disease
Diseases
FEV1/FVC
114
What are the different mechanisms by which the respiratory system is regulated ?
- Control of gas exchange
- Control of gas transport around the body
- Control of breathing using chemoreceptors
115
What is ventilation ?
Ventilation is the volume of air which is moved into the lungs
116
What is perfusion ?
Perfusion is the blood flow in the lungs
117
Where will maximum gas exchange occur in the lungs ?
Ration of perfusion to ventilation is 1.0 this only occurs around rib 3
118
What happens to perfusion and ventilation at the base of the lungs ?
At the base of the lung ventilation and perfusion are both larger than at the apex due to gravity. However the blood flow is greater than the ventilation and so the alveoli are compressed. This means the ventilation/perfusion ration is < 1.0
When ventilation < perfection a shunt is created where blood passed through the lungs (from the right to the left hand side of the heart) without sufficient gas exchange occurring. In these region vasoconstriction occurs.
119
What happens to perfusion and ventilation at the apex of the lungs ?
At the apex of the lung ventilation and perfusion are both smaller than at the base of the lung. However the ventilation is greater than the perfusion and so the capillaries are compressed. This means the ventilation /perfusion ration is > 1.0
When ventilation > perfusion alveolar dead space (dead space in the alveoli) is formed. Blood leaving these regions has a high PO2 then normal and so the vasodilation occurs bringing more blood to that area
120
What is respiratory sinus arrhythmia ?
Respiratory sinus arrhythmia is the change in the heart rate over the breathing cycle. The heart rate increases on inspiration and there is a decrease in heart rate on expiration. This is used to minimise the mis match. During inspiration there would be an increase in alveolar dead space and so your heart rate increases to increase perfusion and decrease alveolar dead space. During expiration there is an increase in shunt and so the heart rate drops to decrease perfusion. This is mainly controlled by the vagus nerve. During inspiration there is a decrease in vagal activity to remove the breaks of the heart and during expiration there is an increase in vagus activity to put on the breaks of the heart.
121
In what two ways can oxygen be transported?
In plasma (3ml) and attached to haemoglobin (197ml)
122
How is carbon dioxide transported in the blood
When CO2 molecules diffuse from the tissues into the blood, 7% remains dissolved in plasma and erythrocytes, 23% combines in the erythrocytes with deoxyhemoglobin to form carbamino compounds, and 70% combines in the erythrocytes with water to form carbonic acid, which then dissociates to yield bicarbonate and H+ ions. Most of the bicarbonate then moves out of the erythrocytes into the plasma in exchange for Cl- ions & the excess H+ ions bind to deoxyhemoglobin. The reverse occurs in the pulmonary capillaries and CO2 moves down its concentration gradient from blood to alveoli.
123
How is oxygen carried in the blood?
Each red blood cell is packed full of haemoglobin and each haemoglobin molecules can carry 4 oxygen molecules. Haemoglobin and oxygen form a oxygenation reaction (Not a oxidation reaction) which is a weak short term bond.
124
What determines the oxygen carried by haemoglobin ?
PO2
125
What determines PO2 ?
Alveolar ventilation
126
What are the names of the different types of haemoglobin?
Adult
HbA2
Foetal
Glycosylated
127
What is adult haemoglobin?
92% of haemoglobin is adult
128
What is HbA2 haemoglobin?
delta chains are replaces by beta chains
129
What is foetal haemoglobin?
gamma chains are replaced by beta chains
130
What is glycosylated haemoglobin?
used to monitor diabetes If levels are high in there blood it indicates that blood glucose hasn’t been well controlled in the last three months
131
What is myoglobin?
another oxygen carrier molecule that is found in cardiac and skeletal muscle (not in the blood). It is more a oxygen storage molecule that a transport molecule. Both myoglobin and foetal haemoglobin have a much higher affinity for oxygen than normal haemoglobin which allows these molecules to extract oxygen from the normal haemoglobin.
132
What 4 things can be used to change oxygen delivery around the body?
pH
PCO2
Temp
[DPG]
133
What is the oxygen saturation of arterial and venous blood?
```
Arterial = 98%
Venous = 75%
```
134
Which direction must the graph move in order for oxygen delivery to increase?
Right
135
The graph of oxygen delivery moves to the right when ?
pH decreases
PCO2 increases
Temp increases
DPG increases
136
Why doesn't oxygen uptake decrease if oxygen delivery increases?
The oxygen uptake is on a plato and so minor movements don't change uptake
137
What are some conditions which can arise if there is failure to control the transport of gas around the body?
Anaemia
Hypoxia
CO poisoning
138
What is anaemia ?
Any state where the oxygen carrying capacity of the blood is compromised
139
What things can cause anaemia ?
Iron deficiency
Haemorrhage
Vit B12 deficiency
140
What happens if Vit B12 levels drop ?
you don't produce enough red blood cells
141
If you have anaemia will you have a normal PO2?
Yes
142
If you have a low PO2 can you have normal oxygen sats ?
No because oxygen sats are controlled by PO2
143
If you have anaemia will you have fully saturated red blood cells?
Yes
144
If you have anaemia will you have normal total oxygen content in the blood?
no
145
What is hypoxia ?
An inadequate supply of oxygen to tissue
146
What are the names of the 5 types of hypoxia ?
```
Hypoxaemic Hypoxia
Anaemic Hypoxia
Stagnant Hypoxia
Histotoxic Hypoxia
Metabolic Hypoxia
```
147
What is Hypoxaemic Hypoxia ?
most common cause of hypoxia. Reduction in O2 diffusion at lungs either due to decreased PO2atmos or tissue pathology.
148
What is Anaemic hypoxia ?
Reduction in O2 carrying capacity of blood due to anaemia (red blood cell loss/iron deficiency).
149
What is stagnant hypoxia?
Heart disease results in inefficient pumping of blood to lungs/around the body
150
What is histotoxic hypoxia ?
poisoning prevents cells utilising oxygen delivered to them e.g. carbon monoxide/cyanide
151
What is metabolic hypoxia ?
oxygen delivery to the tissues does not meet increased oxygen demand by cells.
152
What is CO positioning ?
CO (Carbon monoxide) is created by the incomplete combustion of carbon fuel. It is highly toxic because when inspired it binds to haemoglobin to from carboxyhaemoglobin. CO has a very high affinity for Haemoglobin about 250 times greater than oxygen. It causes hypoxia, anaemia, nausea, headache and cherry red skin and mucous membranes. A person with CO poisoning may have a normal respiration rate (because respiration rate is mainly determined by PCO2 however there is potential brain damage and death. Treatment involves providing 100% oxygen to increase PaO2
153
What nerves control inspiration ?
Phrenic and intercostal
154
Where are ventilatory controls found ?
Pons and medulla
155
What alters the rhythm of respiratory centres ?
Emotion
Voluntary over ridding
Mechano-sensory input
chemical composition of the blood
156
What two types neurons are contained in the respiratory centres ?
VRG and DRG
157
What doe VRGs control ?
tongue, pharynx, larynx, expiratory muscles
allows a Basel tone in the expiratory muscles to allow the expiration to be slow and controlled even when there is no active pushing of air out of the lungs.
158
What doe DRGs control ?
inspiratory muscles
159
Describe central chemoreceptors
Found in the medulla. They are responsible for the primary ventilatory drive. They respond to H+ (PCO2) in the cerebrospinal fluid around the brain. An increase in PCO2 in the blood causes an increase in CO2 in the cerebrospinal fluid which reacts to form H+ which then stimulate the central chemoreceptors which in tern stimulates the respiratory control centres in the medulla and increase the rate and depth of breathing. Increase in ventilation means carbon dioxide is breathed out and the stimulus is removed slowing down respiration. They cant respond to an increase in H+ in the blood because the blood brain barrier prevents H+ from crossing but allows CO2 to cross. We are very sensitive to PCO2 because it is toxic to cells if it builds up. People with chronic lung disease PCO2 can become chronically elevated which means that the brain becomes desensitised to elevated PCO2 and therefore the peripheral chemoreceptors are relied on. This is known as hypoxic drive.
160
Describe peripheral chemoreceptors ?
Found in the carotid and aortic bodies. They are the secondary ventilatory drive. They respond primarily to PO2 and plasma [H+]. A significant fall in the partial pressure (100mmHg down to 60) of oxygen cause a increase in ventilation. Note that peripheral chemoreceptors only respond to partial pressure not total oxygen content.
161
Name to drugs which chemoreceptors are interfered with ?
Barbiturates and opioids
| Nitrous oxide
162
What are barbiturates and opioids used for in control of chemoreceptors?
Barbiturates and opioids depress respiratory centres. An overdose of them results in respiratory failure, decreased sensitivity to pH and so PCO2 and also a decrease in peripheral chemoreceptors response to PO2.
163
What are nitrous oxide used for in control of chemoreceptors?
Nitrous oxide is a common sedative which blunts peripheral chemoreceptors. It is very safe for most people but for people who have hypoxic drive it can be very dangerous.
164
Which systems are used to control the acid base balance within the blood?
Respiratory and renal
165
What is the equation for the bicarbonate buffer system ?
-
166
How do the respiratory and renal system work together ?
The respiratory system and the renal system can both cause an disturbance and remove a disturbance, so if the respiratory system causes a disturbance the renal system will work to remove it and vice versa.
167
How does the respiratory system cause a disturbance to the acid base balance ?
Normally pH is stable because all the CO2 produced is eliminated in expired air however hypo/hyperventilation will alter plasma PCO2 and plasma [H+] will vary accordingly. Hypoventilation, causing CO2 retention, leads to increased [H+] bringing about respiratory acidosis. Hyperventilation, blowing off more CO2, lead to decreased [H+] bringing about respiratory alkalosis
168
How does the respiratory system restore a disturbance to the acid base balance ?
If there is an decrease in pH (H+ increases) ventilation will be stimulated. This occurs in a metabolic acidosis. This removes CO2 which drives the equation to the left reducing [H+]
If there is an increase in pH (H+ decreases) ventilation will be slowed. This occurs in a metabolic alkalosis. This reduces the removal of CO2 which drives the equation to the right increasing [H+]
169
What is the acid base balance equation to calculate pH ?
-
170
what happens to ventilation during exercise ?
ventilation increases in exact proportion to metabolism, but the signals causing this are not known.
The proportional increases in ventilation and metabolism during moderate exercise cause the arterial PO2 and PCO2 to remain unchanged and thus do not drive the increased ventilation.
During very strenuous exercise, ventilation increases more than metabolism. Arterial [H+] increases because of increased lactic acid production. This accounts for some of the hyperventilation seen in this situation.
171
What type of reaction occurs between haemoglobin and oxygen ?
oxygenation
172
What is a metabolic acidosis ?
When the renal system causes an H+ increases and the respiratory system increases ventilation to get rid of Co2 to that H+ is converted to CO2.
