lecture 3: respiratory Flashcards
- what IS daltons law?
Pressure of a gas mixture is equal to the sum of the partial pressures of the gasses in that mix
- what is ficks law?
molecules diffuse from areas of high conc to low conc at a rate
- inversely proportional to the thickness of the exchange surface
- proportional to conc gradient, exchange surface area and diffusion capacity of the gas
*what is henrys law?
At a constant temperature, amount of gas that dissolves in a liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
*what is boyles law?
At a constant temperature, volume of gas is inversely proportional to pressure of gas
- what is charles law?
At a constant pressure, the volume of gas is proportional to the temperature of that gas.
how does the proportion of gases change with oxygen therapy?
more oxygen concentration
therefore a steeper diffusion gradient
how does the proportion of gases change with altitude?
the pressure of the atmosphere decreases but the proportions of gas remain the same
you just breath in less of everything
what happens to the air as it moves down the gas pathway?
it is first
- warmed - cold air is an irritant
- humidified - dry air is an irritant
- slowed
- mixed
overall the amount of oxygen is diluted down as some of it is made into water vapour
what is the total oxygen delivery at rest?
is that enough to supply the body?
- the total delivery is 16 ml / min
- the oxygen consumption is 250 ml/min
- therefore we cannot just rely on dissolved oxygen we must also rely on haemoglobin
what is the overall structure of haemoglobin?
- consists of iron
- at the centre there is tetrapyyrole porphyrin ring connected to a protein chain (-GLOBIN); covalently boned at the proximal histamine residue.
- 4 chain varients
alpha beta gamma delta
**how is HB an allosteric protein?
it changes shape depending on what is bound to it
how does the binding of oxygen change haemoglobin’s affinity to oxygen?
- as more oxygen binds the affinity for oxygen increases
- this is called cooperativity
- 2, 3 DPG binds to the central opening and aids the dissociation of oxygen to the muscles so oxygen is released
- more of 23 DPG is made when muscles are working hard
what is Methaemoglobin?
- it has Fe 3+ instead of 2+ so it has become MetHb
- MetHb does not bind to oxygen methaemoglobinaemia can cause a functional anaemia
*show an oxygen dissociation curve:
**
it is a sigmoid dissociation curve
- means we can get a high amount of oxygen saturated (95%)
what is P50
partial pressure at 50% saturation
used to see how the curve has moved on the oxygen dissociation curve
why might the curve move to the right?
called the BOHR effect situation : exercise due to - increase in temp - acidosis - lowering of PH due to the lactic acid also CO2 goes up and PH goes down - Hypercapnia – elevated CO2. - Increase in 2,3-DPG.
why might the curve move to the left?
- Decrease in temperature.
- Alkalosis.
- Hypocapnia.
- Decrease in 2,3-DPG
just the opposite to exercise
why might the curve by shifted downwards?
- anemia
- anemia means lower Hb conc so they have reduced oxygen but the saturation is still the same
- you basically have less oxygen capacity
why might the curve by shifted upwards?
- polycythaemia
- this is an increase in haematocrit in the blood due to an increase in red blood cell number
- blood flows slower due to more RBCs so slower O2 delivery
why might the curve be moved downwards and leftwards?
CO poisoning
- hb has greater affinity for CO instead of O2
CO results in the affinity of O2 being increased so it wont dissociate in the tissues
- also decreases the capacity of the Hb for O2
what does foetal haemoglobin do?
Has a high affinity so it can take oxygen from the mothers’ blood via the placenta
what does myoglobin do?
♣ A monomeric protein with a hyperbolic ODC.
This is a protein that stores oxygen inside muscles in times of increased muscular activity
- for low intensity long periods of exercise
**how does oxygen transport happen at the alveoli?
- blood arriving to the alveoli is 75% bound to oxygen
- venous blood returning has Po2 of 5.3 kpa where as the alveolar Po2 is 13.5kpa
- this has made a pressure difference
*how does oxygen transport happen at the tissues?
- blood arriving at the tissues has 97% saturation
- The pulmonary system has 2 circulations:
The pulmonary blood supply for oxygenation of blood for the heart.
It’s own blood supply which drains into the above pulmonary arteries.
This means the blood is diluted by this mixed venous blood return - at the tissues the conc of O2 goes down
- the saturation of O2 goes down
** how does plasma Co2 transport work?
- In the plasma, CO2 reacts with water to form carbonic acid.
a. The carbonic acid SLOWLY dissociates (no enzymes present) into a proton and bicarbonate. - In the red blood cell, the same reaction occurs 5000x quicker due to carbonic anhydrase enzyme!
RBCs do most of the CO2 shifting!
how does the red blood cell transport the Co2?
- the bicarbonate ion diffuses out via the AE1 transporter and the chloride ion moves in
- movement of VL in draws water in so it can react with Co2
- Co2 can also bind with amine end of the proteins to from carbaminohaemoglobin.
- these proteins make a good buffer for any excess proteinsinside the RBC
what is the pulmonary transit time?
gas exchange happens within 0.75 s
by 0.25 all of gas exhange is done
what is the pulmonary transit time?
during exercise?
increased blood flow rate means the lines stretch right but gas exchange still has ample room and time.
what is faster at exchanging co2 or o2 and why
co2 because it is more water soluble
how does ventilation perfusion happen?
- the blood flow to the lungs correlates with gravity exerting an influence on blood flow
- this means less blood perfuses the apex
- this is also true of the individual alveoli
- gravity basically stretches the lung down
show the V/Q graph
when we do perfusion/ ventilation
- the base tends towards 0
- the apex tends towards infinity
