Respiration help!!!! Watch

Catherine0004
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1.Why does the body measure carbon dioxide rather than oxygen levels?
I'd be really grateful if anyone could help, only needs to be short answer but i'm not entirely sure what the answer is. Thought it might be to do with hydrogen ions and pH but i'm getting a bit confused.
Thanks.
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Mustard-man
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Erm... Carbon dioxide has slight acidity, a build up would lower pH. Therefore too much carbon dioxide can poison cells.
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Revd. Mike
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Yep, when CO2 dissolves in the plasma it forms carbonic acid, which makes the blood slightly more acidic.
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firestone
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Maybe it's got something to do with the oxygen dissociation curve as well...a high carbon dioxide concentration indicates active respiration, causing haemoglobin to release the oxygen it has bound with to the respiring tissues that require it. But similarly this is true for oxygen so...
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Revenged
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(Original post by firestone)
Maybe it's got something to do with the oxygen dissociation curve as well...a high carbon dioxide concentration indicates active respiration, causing haemoglobin to release the oxygen it has bound with to the respiring tissues that require it. But similarly this is true for oxygen so...
Haemoglobin saturation is not revelent... Receptors measure partial pressure or H+ conc of the blood - they can't measure oxygen saturation of haemoglobin...
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firestone
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I don't know much about measuring haemoglobin saturation, except the Bohr effect (oh yeah that was the term) that I was referring to. According to my text book the blood is less saturated at a high partial pressure of carbon dioxide so this causes haemoglobin to release oxygen by combining with the hydrogen ions from the dissociation of carbonic acid.
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Revenged
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(Original post by firestone)
I don't know much about measuring haemoglobin saturation, except the Bohr effect (oh yeah that was the term) that I was referring to. According to my text book the blood is less saturated at a high partial pressure of carbon dioxide so this causes haemoglobin to release oxygen by combining with the hydrogen ions from the dissociation of carbonic acid.
Yes... What you're saying is true... but it isn't the reason why carbon dioxide levels are monitored... CO2 is measured to make sure that pH is maintained... Not very large changes in plasma pH can kill you...
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mocko
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hello

The body can detect both changes in CO2 and also O2 concentrations. This is because oxygen drives the respiratory system of a person with COPD. (The person with COPD example is not relevant to your question). The chemoreceptors detect slight changes in pH unlike oxygen concentration where they have to be significantly lower to cause a reaction. The pH of blood is 7.35-7.45 a very narrowed range and this is why CO2 concentration will drive the respiratory system. Oh yes and as stated before... CO2 react with carbonic anhydrase to produce carbonic acid and H+ ions. H+ concentration determines pH...

hope this helps
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gyrase
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(Original post by Revenged)
Yes... What you're saying is true... but it isn't the reason why carbon dioxide levels are monitored... CO2 is measured to make sure that pH is maintained... Not very large changes in plasma pH can kill you...
you mean large changes in plasma pH CAN kill you ...?
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fundamentally
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(Original post by Decota)
you mean large changes in plasma pH CAN kill you ...?
Acidosis can kill you rapidly.

It is considered to exist when the pH drops below 7.35 and is generally fatal at below 7.1 That is why there are renal and respiratory mechanisms to regulate the acid-base balance of blood. In addition, there are buffers in the blood that help to smooth out fluctuations in pH.

And the endocrine system plays a role as well, through aldosterone secretion.

http://www.emedicine.com/emerg/topic312.htm
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RyanY
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yeh chemoreceptors monitor the pH level of the blood and co2 forms carbonic acid in plasma, which when detected flows on a homeostatic pathway to avoid acidic blood. Remember haemoglobin is a natural buffer...
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