More Co2 = less brains?

Anders Skarsb| ip693 at lstud.ii.uib.no
Thu Feb 13 15:46:38 EST 1997

Jaimie Polson wrote:
> In <01bc17cd$42cb8560$b049bacd at dnawten.ix.netcom.com> "Nate" <dnawten at ix.netcom.com> writes:
> >Hope I'm not unwelcome in chiming in on this but regarding the displacement
> >of O2 by CO2 on hemoglobin, this is physically impossible.  CO2 binds to
> >the "globin" part of Hb (23% of all CO2 is carried this way, about 70% is
> >carried in the plasma) while O2 is carried by the "heme" portion (98% of
> >all O2 binds to Fe++ ions).  So theoretically both CO2 and O2 can can be
> >carried on the same Hb meaning that an increase of CO2 by itself probably
> >will not cause drowziness.  It probably has to do moreso with an inadequate
> >supply of O2 than anything else.
> >A good example of this would be if someone suffocated in a plastic bag.
> >Drowziness, unconsciousness and eventual death wouldn't be a result of the
> >increased CO2 per se, but due to the lack of oxygen.
> >Hope this answers your question.
> >Nate
> According to Smith & Kampine, "Circulatory Physiology" text...
> A decrease in pH or an increase in CO2 will shift the oxygen dissociation
> curve to the right - ie a greater PO2 is then required for haemoglobin to
> bind the same amount of O2.  If I recollect correctly, this is part of the
> way in which O2 is released from haemaglobin in the tissues. The higher
> level of CO2 caused by metabolic activity increases the release of oxygen
> So presumably, this means that with a higher PCO2 in the blood, less O2
> would bind for a given PO2 - but I don't know how significant this would
> be at any imaginable increase in CO2 levels.
> (And also, this does not account for the body's homeostatic responses to
> reduce the high CO2 - that were kindly explained to me earlier.)
> Jaimie

Allright, this is getting a bit advanced for me here, but I still think
it sounds like someone is confusing CO2 with CO - there is a BIG
difference, as most of you will know. CO2 only suffocates by replacing
the O2 in the air, in reality drowning a victim just like water. O2, on
the other hand, is poison, and destroys the haemoglobin.

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