Respiratory Physiology Flashcards
Why do all cells need oxygen?
To make ATP
How do unicellular organisms get oxygen?
Via diffusion
Describe the passing of air in the lungs from the nose and mouth down in alveoli
nose and mouth > pharynx > larynx > trachea > primary bronchi > secondary bronchi > teriatiry bronchi > broncioles > terminal bronchioles > respiratory bronchioles > alevoli
What is the only area where gas exchange takes place and why does it not occur elsewhere?
In the alveoli, only occurs here but walls are 1 cell thick and everywhere else walls are too think for gas exchange
What are the areas that arent involved in gas exchange but pass air to the areas that are called?
The conducting zone
What parts of the respiratory system or past of the conducting zone and what parts arent?
nose and mouth, pharynx, larynx, trachea, primary, secondary tertiary bronchi, bronchioles, terminal bronchioles BUT NOT respiratory bronchioles and alveoli
What else can the conducting zone by referred to as?
The anatomic dead space (because no gas exchange occurs)
What volume of air is contained in the conducting zone?
150ml
If respiratory bronchioles and alveoli are not part of the conducting zone what zone do they make up?
The respiratory zone where gas exchange takes place
What are the components of the respiratory zone?
The respiratory bronchioles, the alveolar ducts and the alveoli
What is Boyles Law?
Pressure is inversely to volume - as one goes up the other goes down
How can boyles law be applied to respiration? (super long explanation)
In that when you breathe in the volume in the thoracic cavity expands due to the diaphragm flattening and that means the pressure in the thoracic cavity has decreased and is lower than the external pressure which causes air to rush in to balance it again (same for outside - when you breathe out the volume decreases, pressure increases higher than that of the outside so air rushes out)
What is the inspiratory reserve volume?
The volume you can breathe after you have taken a normal breath
What is expiratory reserve volume?
The volume you can breathe out once you have breathed out normally
What is the inspiratory capacity?
The inspiratory reserve volume + the resting tidal volume aka the amount of air you can inhale after you have just expired
What is the resting tidal volume?
The volume inspired and expired in normal breathing
what is the volume of the inspiratory reserve volume?
3000ml
What is the volume of the expiratory reserve volume?
1500ml
What is the inspiratory capacity volume?
3500ml
What is the resting tidal volume?
500ml
What is the vital capacity?
The inspiratory capacity (inspiratory reserve volume + resting tidal volume) + the experiatory reserve volume - aka the volume between forcefully inspiring and forcefully expiring
What is the volume of the vital capacity?
5000ml (3500 + 1500)
What is the residual volume?
The volume of air remaining in the lung after a full expiration (aka the total lung capacity minus the vital capacity)
What is the volume of the residual volume?
1000ml
What is the minimal volume?
The remaining volume in the lung that can only be measured when it is collapsed (about 30-120ml)
What is the functional residual capacity?
The expiratory reserve volume plus the resting tidal volume
What is the volume of the functional residual capacity?
2000ml (1500 + 500)
What is the total lung capacity and how would you work this out?
Vital capacity (IRV + RTV + ERV)(5000ml) plus the residual volume (1000ml) = 6000ml = 6L
What is respiratory minute volume?
The volume of air inspired of expired from a persons lungs per minute
How would you calculate the respiratory minute volume?
Resting tidal volume (500ml) x respiratory rate (12 bpm) = 6000ml/min
What is alveolar ventilation?
The volume of air inspired and expired from the alveoli to outside the body per minute
Why is alveolar ventilation different from respiratory minute volume?
It is less because there is always air in the conducting zone (the anatomic dead space volume of 150ml) that cant be exchanged so only 350ml of new air breathed in actually reaches the alveoli
How do you calculate the alveolar volume?
Air that reaches the alveoli per breath (350ml) x the respiratory rate (12 bpm) = 4200ml/min
Why would shallow rapid breathing not be as affective as 12 breaths per minute?
Because the lower the tidal volume (air breathed in) the less that gets to the alveoli for gas exchanged - a tidal volume of 150ml would mean no new air gets to the alevoli!
What is the atmospheric air pressure at sea level?
760mmHG
What does Daltons Law state about pressure?
That the total pressure is the combined total of the pressures of the individual gaseous compenents - one gases pressure is independent of the other gases in the mix
What are the pressures of the individual gases of a mixture known as?
Partial pressures
What does the contribution of each gas to the total pressure of the mixture depend on?
The percentage of that gas in the mixture
How would you work out the partial pressure of a gas in a mixture?
percentage of gas in the mixture/100 x total pressure
What is the partial pressure of oxygen in air if it takes up 20% of the mixture and the total pressure is 760mmHg?
20/100 = 0.2 x 760 = 153mmHg
What does Henrys Law state?
The amount of gas that diffuses into a liquid is directly proportional to its partial pressure i.e. the higher the partial pressure the more of the gas diffuses into the liquid
What does Henrys Law mean in terms of gas in the alveolus?
The partial pressure of the gas in the alvelous and of the surrounding blood will be the same
What is the partial pressure of oxygen in:
a) atmospheric air
b) the alveolar air
c) pulmonary capillary (in the blood)
a) 150mmHg (20% of total pressure 760mmHg
b) 100mmHg
c) 100mmHg (same as in alveolar according to henrys law)
What is the partial pressure of carbon dioxide in:
a) atmospheric air
b) alveolar air
a) 0.2mmHg (0.02% of total pressure 760mmHg)
b) 40mmHg
What does the partial pressures of these components differ in atmospheric and alveolar air?
Because oxygen is removed and carbon dioxide is added
How are oxygen and carbon dioxide exchanged between the blood and the alveoli?
Exchanged by diffusion from an area of high concentration to an area of low concentration
What two ways is oxygen transported in the blood?
- dissolved in plasma
2. bound to haemoglobin
How much oxygen will be dissolved in the blood?
3ml of O2 per litre of blood
What is the circulating volume of blood?
5L
What is the resting oxygen consumption?
250mlO2/min
How many subunits does haemoglobin have?
Four
What atom is contained in each of the subunits of Hb?
An Fe atom
How does haemoglobin bind oxygen and how many oxygen molecules can it carry per Hb molecule
The O2 binds to the Fe atom of the subunit so Hb can therefore carry 4 o2 atoms per Hb molecule
What does the percentage of hb satured with oxygen depend on?
The partial pressure of oxygen in the blood
When would the percentage saturation of hb with oxygen be about 25%?
When the partial pressure of oxygen is about 15mmHg i.e. in tissues during exercise
When would the percentage saturation of hb with oxygen be about 70%
When partial pressure of oxygen is about 40mmHg i.e. in tissues at rest
When would the percentage saturation of hb with oxygen be almost 100%?
when the partial pressure of oxygen is about 100mmHG i.e. in the lungs
What happens to the percentage of hb satured with oxygen as Ph decreases at a constant partial pressure oxygen?
It decreases
Why does a decrease in ph mean a decrease in the amount of oxygen bound to hb?
Because a lower ph means an increase in H+ ions which bind to the Hb and change its structure meaning it is less likely to bind to o2
What happens to the percentage of hb saturated with oxygen as the temperature increases at a constant partial pressure of oxygen?
It decreases
Why does an increase in temperature mean less oxygen bound to hb?
Because in more metabolically active tissues there is an increase in temperature and the percentage of oxygen bound to hb decreases because it is being released into the tissue
What are the three ways in which CO2 is transported in the blood and what percentage of CO2 is carried in this way?
- Dissolved in plasma (10%)
- As carbamino compounds e.g HbCo2 (30%)
- As bicarbonate (60%)
what is Co2 and H20 converted to?
Carbonic acid
What converts co2 and h2o to carbonic acid?
Carbonic anhydrase
What is carbonic acid then converted to?
Bicarbonate ion and hydrogen ion
What controls rhythmic breathing?
the respiratory rhythmicity centre of the medulla oblongata
What does the medulla oblongata contain that are involved in regulating breathing
medullary inspiratory neurones
What do the medullary inspiratory do that regulates breathing?
They drive motorneurones which innverates the diaphragm and intercostal muscles
What is the basis of chemical control of respiration?
They fact that it is changes in the chemical enviroment that innverate the medullary inspiratory neurones to control breathing
What happens when the medullary respiratory neurones are activated?
Inspiratory muscles contract and inspiration occurs
What happens when the medullary respiratory neurones are inhibited?
Inspiratory muscles relax and expiration occurs
What 4 things can innverate the medullar inspiratory neurones and are said to have chemical control over breathing?
- The brain
- Drugs
- Pulmonary stretch receptors
- Chemoreceptors
Why would the brain control the medullary inspiratory neurones?
If you need to speak or sing etc.
What drugs inhibit the medullary inspiratory neurons?
Morphines and barbiturates
How do pulmonary stretch receptors affect the medullary inspiratory neurones?
If they sense lung inflation they inhibit them
What are chemoreceptors?
A sensory cell or organ that is sensitive to its enviroment and picks up chemical signals
Where are central chemoreceptors located?
In the medulla
Where are peripheral chemoreceptors located?
In the carotid bodies and aortic bodies on the heart
What causes central chemoreceptors to show increased activity?
When aterial PCO2 is increased it is converted to bicarbonate and hydrogen ions - changes in the H+ ion concentration is what the chemoreceptors respond
What causes the peripheral chemoreceptors to show increased activity?
changes in arterial PO2 and PCO2 (more specifically changes in H+ ions)
What is the dominant influence on chemoreceptors; PCO2 changes or PO2 changes?
PCO2
Why is PO2 not the dominant influence?
Because in order for PO2 to have any affect on breathing is has to decrease below 60mmHg and even then it will only increase the respiratory rate by 50%
Why is PCO2 the dominant influence on chemoreceptors?
Because a 10% rise in arterial PCO2 will double the respiratory rate even if PCO2 is normal
