AFAIK, we do not, in fact, have any biological system that detects oxygen in the air. What we use instead is detection of the things that are typically present when oxygen is not. Like CO2 concentration. This is what makes a room “feel stuffy”, CO2.
I don’t think this invalidates your point at all, of course you have a valid argument despite the biological misunderstanding here.
The only reason I know this is when looking into the whole, capital punishment by nitrogen hypoxia thing, I kinda stumbled into a lot of information. We don’t generally detect nitrogen nor oxygen in any way, shape, or form, since it’s quite plentiful in the atmosphere of the earth (78% nitrogen, 21% oxygen), there’s not much reason to. We’ve never needed a biological trigger to say “there’s oxygen here” because there’s never been situations where that hasn’t really been true until very very recently (eg. Closed systems like submarines, aeroplanes, vessels that go into high orbit/space, etc).
Looking at the evolution of it, any such space will accrue toxic/deadly levels of atmospheric gases, long before the oxygen is consumed. So we have biological processes to detect atmospheric toxin levels, with one example being CO2. According to some data I’ve read, CO2 freely is absorbed and expelled by the body through the blood via the alveoli (lungs), which makes the amount of CO2 in your blood a function of atmospheric CO2 levels, which may slightly waiver due to your physical workload. As you produce CO2 within your body from metabolic activity, either from regular metabolic tasks or through physical exertion, the rise in blood CO2 levels is expelled by the blood through equilibrium with the surrounding atmosphere. Simply, if you have higher CO2 concentration in your blood than there is in the atmosphere, it will diffuse towards the atmosphere (I’ll reiterate that the process works in reverse too).
High CO2 concentration in your blood affects your blood pH and can create an acidic environment, which the body can easily detect.
As far as I’m aware, there’s no similar biological process to detect oxygen levels, either directly or indirectly.
This is the danger of nitrogen hypoxia. If you’re in a low CO2 environment which is devoid of oxygen (or has very little atmospheric oxygen, not enough to sustain human life), with most of the o2 concentration being replaced by nitrogen instead, your body can still expel CO2, but cannot obtain the o2 required to survive. Since there’s no mechanism to detect this, your blood o2 levels drop to levels which are incompatible with living while you remain unaware that a problem exists.
Thus, you can easily perish when your o2 saturation drops to nil, with no indication that you’re at risk of dying.
Sorry for the dissertation, this is just something I find incredibly fascinating about biology. I hope I didn’t bore anyone too much.
Disclaimer: I’m not a biologist or scientist, I’m just some guy with ADHD, and I’ve hyperfocused on this subject a couple of times. If anything I’ve said is incorrect, I invite corrections. If possible, please link additional resources for further reading and my ADHD brain will thank you very kindly for the effort.
AFAIK, we do not, in fact, have any biological system that detects oxygen in the air. What we use instead is detection of the things that are typically present when oxygen is not. Like CO2 concentration. This is what makes a room “feel stuffy”, CO2.
I don’t think this invalidates your point at all, of course you have a valid argument despite the biological misunderstanding here.
The only reason I know this is when looking into the whole, capital punishment by nitrogen hypoxia thing, I kinda stumbled into a lot of information. We don’t generally detect nitrogen nor oxygen in any way, shape, or form, since it’s quite plentiful in the atmosphere of the earth (78% nitrogen, 21% oxygen), there’s not much reason to. We’ve never needed a biological trigger to say “there’s oxygen here” because there’s never been situations where that hasn’t really been true until very very recently (eg. Closed systems like submarines, aeroplanes, vessels that go into high orbit/space, etc).
Looking at the evolution of it, any such space will accrue toxic/deadly levels of atmospheric gases, long before the oxygen is consumed. So we have biological processes to detect atmospheric toxin levels, with one example being CO2. According to some data I’ve read, CO2 freely is absorbed and expelled by the body through the blood via the alveoli (lungs), which makes the amount of CO2 in your blood a function of atmospheric CO2 levels, which may slightly waiver due to your physical workload. As you produce CO2 within your body from metabolic activity, either from regular metabolic tasks or through physical exertion, the rise in blood CO2 levels is expelled by the blood through equilibrium with the surrounding atmosphere. Simply, if you have higher CO2 concentration in your blood than there is in the atmosphere, it will diffuse towards the atmosphere (I’ll reiterate that the process works in reverse too).
High CO2 concentration in your blood affects your blood pH and can create an acidic environment, which the body can easily detect.
As far as I’m aware, there’s no similar biological process to detect oxygen levels, either directly or indirectly.
This is the danger of nitrogen hypoxia. If you’re in a low CO2 environment which is devoid of oxygen (or has very little atmospheric oxygen, not enough to sustain human life), with most of the o2 concentration being replaced by nitrogen instead, your body can still expel CO2, but cannot obtain the o2 required to survive. Since there’s no mechanism to detect this, your blood o2 levels drop to levels which are incompatible with living while you remain unaware that a problem exists.
Thus, you can easily perish when your o2 saturation drops to nil, with no indication that you’re at risk of dying.
Sorry for the dissertation, this is just something I find incredibly fascinating about biology. I hope I didn’t bore anyone too much.
Disclaimer: I’m not a biologist or scientist, I’m just some guy with ADHD, and I’ve hyperfocused on this subject a couple of times. If anything I’ve said is incorrect, I invite corrections. If possible, please link additional resources for further reading and my ADHD brain will thank you very kindly for the effort.