Alright, we've got a big, long example here, so let's start reading. It says hyperventilation occurs when the rate and or tidal volume of ventilation increases to a point where the composition of alveolar air more closely resembles atmospheric air. Alright, so just starting off, remember we said that there's actually a big difference between the composition of the air in the alveoli and the air in the atmosphere around us, because when you ventilate your lungs, you only replace a portion of that air in the alveoli with each breath. Alright, here we go, we're going to keep reading. It says, based on the above description, when hyperventilating, would you expect the relative change in partial pressure of carbon dioxide or the partial pressure of oxygen to be greater? Alright, what do you think? You're breathing really, really hard, so that air in the alveoli resembles more of the atmospheric air. Relatively, which is that going to affect more, the partial pressure of carbon dioxide or the partial pressure of oxygen? Well, we looked at these values in a table, and while you probably don't need to remember the exact values, you should be relatively familiar with what they are. And so I'm just going to write this out again. We had the partial pressure of oxygen and the partial pressure of CO₂ in both the atmosphere and the alveoli. And we said the partial pressure for oxygen in the atmosphere was about 159 millimeters of mercury, and in the alveoli, it was about 104 millimeters of mercury. And for carbon dioxide, we said it was 0.3 millimeters of mercury in the atmosphere, really, really low, and it was 40 millimeters of mercury in the alveoli. So as I look at these, I think if I'm breathing really, really hard, my alveoli is going to have a composition more like atmospheric air. Which one does it affect more? Well, relatively, as I look at these, well, 104 is about two-thirds the amount of the atmospheric air. So they're pretty close. Whereas the difference for the pressures in carbon dioxide goes from 0.3 to 40, That's a more than 100 fold change. So relatively, that's a huge change in carbon dioxide, but that's not that much of a change for oxygen. So which one is it going to affect more? I'm going to say the partial pressure of CO₂. Alright, we're going to keep reading here. It says the normal partial pressure of oxygen and carbon dioxide in arterial blood is listed below. Next to each, write an up arrow or down arrow based on whether you expect that value to increase or decrease during hyperventilation. Alright, well, now we're talking in the blood. So here it says the partial pressure of carbon dioxide in that arterial blood, that blood leaving the alveoli and headed to the tissues, is 40 millimeters of mercury, and the partial pressure of oxygen is 100 millimeters of mercury. So now, if we change that alveolar air to be more like atmospheric air, how do we expect these to change? Well, first up, what do you think about carbon dioxide? Well, Henry's law, right? It tells us that whatever that partial pressure is is going to tell us how much of that gas can dissolve into the liquid, in this case, the blood. So if we take that alveolar air and we make it more like atmospheric air, here, we are really reducing the partial pressure of carbon dioxide in the alveoli. And so that should really reduce, or a down arrow, the amount of carbon dioxide that will dissolve into that blood. Alright, we can do the same thing for oxygen here. So oxygen, 100 millimeters of mercury is what it normally is, leaving, the alveoli in that arterial blood. Well, we look here if we make this alveoli more like atmospheric air, well, we're increasing that partial pressure. So I would expect more, or I'll draw an up arrow, to dissolve into the blood. Alright, one more here. It says hemoglobin leaving the alveoli is usually 98% saturated, meaning 98% of the hemoglobin molecules are carrying the maximum amount of oxygen molecules. Knowing this and based on your previous answers, would you expect hyperventilation to affect the amount of oxygen molecules carried by the blood or carbon dioxide molecules more? Alright, so let's think this through. Which of these in the blood is going to be affected more, especially now that we're thinking of hemoglobin? Alright, so what it says there is that most of the oxygen in the blood right? Remember, oxygen isn't as soluble in blood, and so it's being carried by those hemoglobin molecules. But at our normal partial pressure, the hemoglobin is 98% saturated, meaning it's carrying about all the oxygen it can. Well, remember carbon dioxide, especially in our arterial blood, it's really just traveling around dissolved in the plasma because carbon dioxide is much more soluble. So if we change those partial pressures, which is going to be affected more? Well, if we raise the partial pressure of oxygen, we're not raising it relatively that much, and most of the oxygen is being carried by the hemoglobin anyway, and it can't carry that much more. So it's probably not going to affect how much oxygen is in the blood very much at all, but the carbon dioxide again, most of that carbon dioxide is in solution, and so if we really change the partial pressure, that is going to really change how much can get dissolved into the blood. So for that reason, I think that carbon dioxide is going to be affected much more when we're talking about how much of those molecules are actually in the blood when you're hyperventilated. Alright, that was a big long problem, but we worked through it. Hopefully, you were there with me. More practice to follow. See you there.