Breathing is Confusing Me

[GoBlue!]

Good diagram, Mark, especially the lower portion w/ the ppO2s listed. Just a point of clarification for those following the numbers & details, the ppO2s thrown around here (& in Nitrox calculations) are the partial pressures of inspired gas. They are not the same as the partial pressures of gases in the body that actually lead to physiological changes. Related, yes, but equivalent, no.

Jim

 

[GoBlue!]

Woah, Im getting speed wobbles here, this seems to contradict the first bit. Let me get this straight, it is not the levels of bicarbonate nor the levels of pCO2 disolved in the bloodstream, rather the creation of bicarbonate in the CSF, realeasing a free hydrogen ion that the receptors respond to.

There are multiple backup systems. The blood chemoreceptors sense pCO2, H+, and pO2. The medullary chemoreceptors primarily respond to free hydrogen ion (that is created when dissolved blood pCO2 crosses the blood-brain barrier and is subsequently buffered by the bicarbonate system). Realize that pCO2, pH, and HCO3- concentration are all interrelated; it's just that some pretty clever physiologists separated out each of their actions (or inactions) on the chemoreceptors.

so as blood CO2 is disolved and is measured as gas tension rather than partial pressure, there is no effect on it due to changing ambient pressure except at the change of gas phase on the blood/alviolar boundary because of the effects on the difuusion gas gradient.

And you body makes it at the same rate anyhow..

I'm actually not positive about whether or not there is a change in blood pCO2 at depth, but don't think there would be since it's production is unrelated to depth. If I run into one of the pulmonary physiologists at work, I'll run it by them.

Jim