zor
Well-Known Member
I think the idea is the lungs absorb only a certain amount of oxygen and/or vapor up to about 5 seconds. they've absorbed enough at that point and need new fresh oxygen to re activate absorption receptors. this is the benefit of re breathing to re activate receptors once the lungs have taken in all they are going to take in. I typically re breathe about three times some times if the vapor is smooth...
Unless I am misunderstanding you, I don't think that is quite correct, otherwise we'd have a lot of trouble holding our breath for longer than 5 seconds!
O2 and CO2, in particular, travel across a concentration (or pressure) gradient to get from lungs to blood and vice versa, respextively. You don't need "fresh" oxygen, O2 that is still in your lung cavity doesnt go bad or anything like that, it is still there and will eventually be absorbed. Increasing hemoglobin, improving one's metabolism, and a few other things can allow one to hold one's breath for longer, again the air in the lungs does not expire or anything of the sort!
Oxygen binds to hemoglobin in the red blood cells, those receptors can certainly get saturated but just as quickly as it binds is it used in aerobic respiration (to generate ATP, aka energy for cells).
On a side note, our bodies have systems to respond to low levels of oxygen as well as high AND low levels of carbon dioxide in our blood (too little CO2 can induce alkalosis, which is very undesirable).
Anything beyond a shallow look into how human respiration and cellular respiration work is waaaaay beyond the scope of the question @juneshayek originally asked but I really, really encourage you guys to look online or elsewhere to learn more about this, there is a bit of misinformation flowing in this beloved forum!
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