 All right, poundlets, let's talk. Let's talk about pH homeostasis. And let's talk about this because your blood pH levels have to be between 7.38 and 7.42. What? Are you serious? We get much more specific than this. That's pretty darn specific. It's slightly basic on our pH scale. Remember, pH is nothing more than a measure of hydrogen-ion concentration. And there are three ways that your system will maintain pH. If you go out of this range, if you go between 7, okay, I don't know how to do my little alligator things, I want to say less than 7 or greater than 7.7. Do you know what I'm talking about? If you go that direction, then you're dead. That's a bummer. Don't do that. If you are below 7.38, you're more acidic than the homeostatic range and that you actually end up with symptoms of a condition called acidosis. Makes perfect sense. Acidosis results in kind of sluggish function. So coma. You can go into a coma if your pH is too acidic. On the other hand, if you become alkalinic, metabolic alkalosis, you go into alkalosis, not acidosis. And alkalosis results in twitchiness, like hyper-excitability of the nervous system. In fact, if it's extreme, if it's getting really bad, your muscles can actually cramp because they become so excitable. If it's cramping, if it happens in, for example, your diaphragm, which is a skeletal muscle, you aren't going to be able to breathe anymore. And because you know all about ventilation, you know why you can't breathe if your diaphragm is not working. So really, pH homeostasis is a huge deal and we better get it right. So there are three tools in our toolbox that we're going to use to manage pH. And I'm going to do them in order of speed and non-efficacy. So the fastest, but the least long-term effective is a buffer system. Remember, buffers resist changes in pH even if you add acid or base. And we have the best buffer on the planet in our bodies. Right now, in fact, our kidneys filter out one pound of the stuff every single day. And that is bicarbonate ions, HCO3 negative. Bicarb ions are an excellent buffer. You add hydrogen ions to that and you're going to push the equation. I can't help it. We just got to write it all down. Remember, our entire equation, we had water and carbon dioxide makes carbonic acid H2CO3, which will dissociate into hydrogen ions and bicarbonate ions. Remember that? Because we talked about how the blood carries carbon dioxide in the form of bicarbonate ions. Bicarbonate ions are a buffer because you can actually end up, if you add acid to the system, the bicarbonate ions are going to combine with the hydrogen ions and get water and carbon dioxide. That's awesome. Like, we'll take that any day. If we add base to the system, the hydrogen ions in the system will combine with the base and shift the whole thing. And so you can actually prevent changes in pH just by having this buffer in the system. Now, the deal is it's super fast, but it's easily overwhelmed. There is a point at which buffers stop working. So you can add acid and base to a buffered solution, and once you hit the buffering range, the pH won't change, no matter how much you add until you overwhelm the buffer. Once you overwhelm the buffer, then you're going to have a rapid change of pH again. So they're awesome, they're critical, they deal with short-term changes in pH. Like, dude, you held your breath a little bit too long, you have too much carbon dioxide, we got this. We got it covered. But if you are holding your breath for too long or you have some other issue with your pH, that's when we need somebody else to come into the mix. We already know who else is going to be a player. The respiratory system. Sensory receptors that detect changes in pH that are found in your bloodstream, or found in your blood vessels. They're monitoring pH changes. 75% of the problems are dealt with by the respiratory system. It's easy. Just breathe, breathe a little bit more, breathe a little bit less. Like, you don't even think about your breathing, and you don't even think about changes in your breathing. The moments when you take that really deep breath, why did you just bust a deep breath out? Often it's because you're just making a slight adjustment to your pH of your blood. Respiratory system is pretty quick, and it's pretty efficient, but it ain't nothing on the kidneys. My friend's the kidneys, and that's what we're going to talk about next. The kidneys aren't messing around. The kidneys do the best job, but it takes the longest amount of time. So you're not going to see changes. Actually, you're going to see them. You are going to see them when you drink baking soda water in the P lab. You've probably already done that for this class. So when you drink all that basic solution, your P is going to change its pH relatively quickly. So that's actually within, you know, it takes maybe an hour or so, and you're going to actually see results, changes in pH, as opposed to respiratory system being much quicker within a couple of breaths, and buffers instantaneously when they come in contact with a change. So there's two places that we're going to deal with pH adjustments or homeostasis in the kidneys. We're going to look at the proximal convoluted tubule and mechanisms in the collecting duct and distal convoluted tubule, mostly collecting duct. So let's start out with a proximal convoluted tubule where remember we're reabsorbing a pound of baking powder, baking soda, every 24 hours. Dude, does that blow anybody else's mind into tiny little bits? I can't stand it. That's an entire box of baking soda. That's so crazy. Thank goodness for baking soda or else you would be having a comatose or twitching and not able to breathe. That'd be sad story. Okay, I'll be right back.