The Respiratory System

In this episode, we learn about the Respiratory system, focusing on the air pathway, the bicarbonate buffer system, alkalosis, acidosis, and more! If you have any questions, suggestions, or corrections, please email themcatquizshow@gmail.com

Transcript

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SPEAKER_02 0:08

But you may want to stop changing your way. Changing your name.

SPEAKER_03 0:30

Thanks for the intro, Pat Collins. Welcome everyone to the MCAT Queer Show. I'm Eminem, and joining me today, as always, is my favorite host, Isa Hutt. Let's not waste any time and get right into the episode. But first, if you haven't listened to the intro episode yet, make sure you do that first. So today's topic is the respiratory system. Asa, are you ready to start with the first question?

SPEAKER_00 0:51

Yep. Thanks for the intro, Marshall. Let's get started. Round one, fight. And the first few questions are gonna be some review from previous episodes. So let's see how well you can recall. Okay, first question. In a hot environment, what happens to the size of the blood vessels and what happens to the speed? So in a hot environment, you know, you're out on the beach, you will have vasodilation, dilating mean to get bigger, and the velocity of blood will decrease. Why is that happening? Well, it's helping the body release heat through a larger surface area. Okay, so for example, in a cold environment, can you tell me what happens to the size of the blood vessels and the velocity of blood? So intuitively, the blood vessels will constrict, so basoconstriction they'll get smaller, and the velocity of blood will increase. And this is going to help the body conserve heat through a smaller surface area. Okay, a few more review questions. Which law shows that pressure and volume are inversely proportional to each other when moles and temperature are kept constant. And this is Boyle's law. Can you tell me what Boyle's law is? So you can say the equation with the letters, but I also want you to say it out loud what those letters represent. So Boyle's law is P1 V1 equals P2V2, where P equals pressure and V equals volume, because pressure and volume are inversely proportional. You increase one means you decrease the other. Pathogens are removed from the lungs through which process? And this is called the mucociliary escalator. Right, we're combining mucus and cilia. Okay, with regards to the deoxygenated blood pathway, the right ventricle pumps the deoxygenated blood through which valve to reach the pulmonary artery? And it's going to be pumped through the pulmonary valve to reach the pulmonary artery. Right, we're sending that blood from the right ventricle to get oxygenated. So after it goes into the pulmonary artery, which atrium receives oxygenated blood from the lungs through the pulmonary vein? And this would be the left atrium. It's receiving that oxygenated blood and it's getting ready to be pumped for the rest of the body. Blood and arteries are mostly oxygenated, except for which artery? And this is the pulmonary artery. Remember, there are two exceptions to this vein and artery rule where there's oxygenated blood in arteries and deoxygenated blood in veins. The only two exceptions are in the lungs and in the umbilical cord. We can always use the rule A for away, so arteries are sending blood away from the heart, and veins are sending blood towards the heart. So blood in veins are mostly deoxygenated, except for which vein? Yes, that would either be the pulmonary vein or the umbilical vein. Let's get started now with some new fresh questions regarding the respiratory system. Okay, what are the nostrils in the nose called? We're looking for the medical or scientific term. And these nostrils are called NERES. NARES. N-A-R-E-S NARES. In the nose, air travels through the nasal cavity where pathogens get filtered by the mucous membrane and tiny nasal hairs called what? So there's tiny little hairs in your nose, those are called vibracy. It looks weird the spelling, looks like it should be pronounced vibracee, but it's pronounced vibracy. But I've heard other pronunciations as well. When the epiglottis is open, air travels down what? Which is where vocal cords are located that allow for speech. And this is called the larynx. So the air will travel down the larynx. After passing through the larynx, air travels down what? aka your windpipe, this one should be easy. Your trachea. So after your trachea, what does it split into? There's two of them. And these would be called your bronchi. And from your bronchi, what do those split into? There's a lot of those. And these are called bronchioles. Bronchioles. So in the lungs, bronchioles are made up of many what? Which is where gas exchange occurs. And these are called alveoli. Alveoli. A little trivia for you. Is the right or left lung smaller? And this is actually your left lung. It's about 10% smaller than your right because it shares a space in the chest cavity with the heart. And that's positioned slightly to the left, right? Your heart slightly on your left. And so to accommodate this, the left lung features sort of inward curve, and that's known as the cardiac notch. So a bit of trivia for you there. And then also related, how many lobes do each lung have, like your right and your left lung? Do you know? So your left lung contains only two lobes, has the superior and inferior lobes. And the right lung contains three actually, as the superior, middle, and inferior. It's a bit wider, a bit heavier, but it's actually a bit shorter, and that's to accommodate the liver, which is directly beneath the right lung. So the right lung, a bit shorter, but it's bigger. Three lobes located above the liver. And then the left lung, it's only two lobes smaller, and that's sharing space with the heart. Okay, next question. The membrane closest to the lungs is called what? And this is called the visceral pleura. So in contrast, what is the membrane further from the lungs called? And that is called the parietal pleura. So in all this, I want you to try to start understanding meanings of words instead of just rote memorization. And it's easy to remember which is which based on what the words mean: visceral and pleura. So visceral refers to the soft internal organs of the body. So think of heart, lungs, liver, intestines, and parietal. Parietal means relating to a wall. So the parietal pleura lines the inner walls of the chest cavity. And the visceral pleura covers the outer surface of the lungs. So do you see how visceral refers to those inner organs, those soft tissues? So that'll be the lungs, covers the outer surface of the lungs. It's close to the closest to the lungs. And then the parietal pleura is relating to walls. So it lines the inner walls of the chest cavity. So on the outside of that visceral pleura. Okay, so um just try and think of the meanings and don't just memorize it for the sake of memorization, because it's gonna help you with the MCAT and it will also help you later in your medical career. So between the visceral and parietal pleura is what? It's a space, it has a name. This is called the intra-pleural space. And that again makes sense based on what the prefix intra means, means inside or within. So it's in that space between the two pleura, visceral and parietal, we have the intra-pleural space. You know, most of these names are pretty intuitive, and a lot of times they just describe medical terminology in your body. The only times where it can get difficult is where some organs and things are named after the scientists who discovered them. And then there's no connection based on Latin or Greek prefixes. But for all these easy ones, it's good to start making a mental note in your head of what they mean. Okay. What is Henry's law? Henry's Law. A less common law than the other ones we've talked about, but Henry's law is C equals K subscript H P subscript gas. So I always say we need to say the words, not just the letters. So C refers to the solubility in molarity. K subscript H is Henry's law constant in moles divided by ATM or atmospheres. And P subscript gas is the partial pressure of the gas in atmospheres. So we can say that solubility equals Henry's constant times the partial pressure of gas. And what is Henry's law useful for? Well, Henry's law is basically referring to, it's stating that the amount of gas that dissolves in a liquid is directly proportional to its partial pressure above that liquid. So in the respiratory system, this is important because it explains how oxygen and carbon dioxide are exchanged between the air in the lungs and the blood in the pulmonary capillaries. So it's explaining the gas exchange. If that doesn't like make much sense, because I know it's a bit of a trickier law to understand, feel free, just look up a YouTube video. Not everything is going to make sense over an audio format, but that's the whole point of this podcast is to identify gaps in your content knowledge and fix those gaps so you can streamline your content review and get to those practice questions. Because that's ultimately the most important way you're going to increase your score on the MCAT, is practice questions. So if you don't understand Henry's Law, look it up. Okay, next question: which muscles contract during inhalation? So inhalation is an active process, and what it's doing is creating a vacuum that draws air into your lungs. So think about that. Which muscles would be contracting? Main ones are the diaphragm and the external intercostal muscles. So the diaphragm, it's that large dome-shaped muscle below your lungs. And when it contracts, it flattens, it moves downwards. So think about this kind of dome-shaped thing beneath your lungs. Look at a picture, it's actually really easy to visualize when you look at a picture. It's a bit of a semicircle. When it contracts and moves downward, it flattens. So it goes from a semicircle to being flat, it moves downwards. What this doing is it's increasing the space in your chest cavity, right? It's making a vacuum. When you increase that space, air is going to rush in, right? Like if you have a if you have a huge room, this is just basic um concentration gradients. You know, if you have a smaller room versus a bigger room, the air is going to flow to the place of lower pressure, right? It's always going to flow to a place of lower pressure. And when you make a bigger space in your lungs, in your chest cavity, you're lowering the pressure. And that air is going to fall. It's going to fall the lower pressure. Additionally, the external intercostal muscles, those are the muscles located between your ribs. And when they contract, they pull your rib cage upward and outward. And it's expanding the horizontal volume of your chest. So the diaphragm is expanding the vertical space. The external intercostal muscles are expanding the horizontal volume of the chest. And there are also some accessory muscles that are contracting. These are a bit more niche and during heavy breathing, so we're not going to cover those. So now let's look at the opposite. Exhalation. What muscles are contracting during exhalation? And let's just start when you're relaxed at first. You're just like, you know, chilling, not doing much, doom scrolling, rotting away and wasting your life. Which muscles are contracting during that process? And actually, there's none during the relaxed process. Because exhalation in the relaxed process, when you're just sitting and chilling, is a passive process. So the diaphragm and external intercostal muscles are actually just relaxing and they're returning to the resting positions. So now, when they return to the resting positions, the chest cavity gets smaller. And that's going to cause the air to be forced back out. Okay? So nothing is actually contracting during the relaxation, exhalation. But how about during active exhalation? Let's just say it's your brother's birthday and it's and they have a cake in front of them, but you want to take the shine away from them. You want them to suffer and not feel the excitement of their birthday, and you blow the candles out for them. You don't want them to blow them out, their own candles, because that's the kind of person you are. Which muscles are being used here? Or which muscles are contracting here? So when you're exhaling actively, your body is recruiting your internal intercostal muscles and your abdominal muscles. Okay? So these muscles are contracting, they're compressing the chest, they're pushing the abdominal organs upward, and they're forcing the air out of the lungs. So internal intercostal muscles and the abdominal muscles. Those are contracting during active exhalation. Okay, next question. A substance called what prevents alveoli from collapsing during inspiration? And this substance is called surfactant. It's extremely important and it prevents this collapse by reducing surface tension. Okay, let's talk about the bicarbonate buffer system. First question is tell me, what is it? Give me the formula. And for this question, I'm gonna give you a bit more time because remember, this podcast is not a passive podcast or it shouldn't be. You're gonna get the most benefit out of answering the questions back. For example, I'm listening to some podcasts right now, they're called Coffee Break, so I've listened to Coffee Break French. And part of the process of learning is repeating back the words after the teacher says the word. So in this podcast, you're gonna get the most benefit. This is a reminder, I'm sure you guys have already heard this before, but if you answer the question back, because you're trying to actively recall what you already know. Uh you're forcing to work on that retrieval aspect of memory. We're gonna get into that in the PsychSoch podcast episodes that are coming out. But you need to try your best to answer them. Okay, just give it a shot. If you don't know, say something random, but you have to keep trying for each question. So if you're not doing that, try your best to start. Uh for this question. Remember that the question was tell me the formula for the bicarbonate buffer system. I'm gonna give you 12 seconds. There we go. Okay, I hope you had enough time. If not, just pause the podcast if you can. So the bicarbonate buffer system formula is CO2 plus H2O. We have this little dual equilibrium arrow, means there's an arrow going back and forth. H2CO3, we have another one of those equilibrium arrows, H plus plus HCO3 minus. Like I said, it doesn't mean anything to us. We're just gonna say the uh letters and numbers. We need to actually say what they are. So again, carbon dioxide plus water, equilibrium arrow, carbonic acid, equilibrium arrow, hydrogen ions plus bicarbonate. Okay, hard to do over audio form, but I hope you understood what that meant. Again, carbon dioxide plus water goes to carbonic acid, goes to hydrogen ions plus bicarbonate. Okay, so what does all this mean? Like let's try to decipher this. This is a extremely important and high yield uh formula that comes up on the MCAT. So what these equilibrium arrow means is means it can go either way. It means that it's not like you know, 3 plus 2 equals 5. This formula can go in reverse order. We can say instead, HCO3 minus plus hydrogen ions goes to H2CO3 goes to H2O plus CO2, right? We can go back and forth. And understanding how this formula works is gonna be very important. So I'm gonna ask you a few questions here about it, and at the end I'm gonna try to summarize what I think is the most important. Um, so first question A faster respiratory rate means what in terms of oxygen and carbon dioxide. If you breathe faster, you know, you're hyperventilating. What does that mean for oxygen and carbon dioxide? It means more oxygen and less carbon dioxide, right? You know, you're going maybe you were breathing really fast because you just ran a race. And you're out of shape, so you ran um 16 seconds on your 100 meter dash. You are breathing fast and you're breathing in more oxygen and less carbon dioxide. Okay. So how about a slower respiratory rate? Intuitively, what do you think that means? That means we are doing breathing in less oxygen and more carbon dioxide.

SPEAKER_05 20:34

Right? Okay.

SPEAKER_00 20:39

What can respiratory acidosis be caused by? Just thinking about respiratory rate. What can respiratory acidosis be caused by? So acidosis means our blood is becoming more acidic, and that can be caused by a decreased respiratory rate. Decreased respiratory rate. I'm gonna ask you another question. I'm gonna explain this if it doesn't make sense. So respiratory alkalosis may be caused by what? That may be caused by an increased respiratory rate. Alkalosis means the blood is becoming more basic, and this is gonna be the opposite of acidosis, it's gonna be caused by an increased respiratory rate. But how about during metabolic acidosis? How does the body compensate during metabolic acidosis? So that means your blood is already pretty acidic. What is gonna happen to your breathing rate to balance that out? And the answer is that you're going to increase your respiratory rate because you want to essentially make your blood more basic. You want to balance that out, right? So therefore, during metabolic out. How does your body compensate by respiratory rate? This should be easy. It should be by decreasing respiratory rate. You want to make your blood more acidic because it's too basic and you're going to decrease respiratory rate. Okay, so let's just examine that for a little bit here and understand why that's happening. If you've got all these questions right, bang on, you know, you're good to go. You can even skip this part. But if you didn't, try to understand how this formula works. So anytime you increase anything in this formula, you're gonna shift it a certain way. Okay, so if you have a pencil and paper, if you're able to write out this formula down, our bicarbonate buffer system, you need to understand this point. So we go back to our first question. So we said faster respiratory rate means more oxygen, less carbon dioxide. So what you're gonna do in your formula is you're gonna put a big arrow pointing downwards for carbon dioxide. You're gonna say less carbon dioxide beside that CO2. You don't have a pencil and paper, just imagine in your mind we're decreasing the number of amount of carbon dioxide. Okay. When we decrease anything in a formula, it's gonna shift a certain way. Okay? And this is Le Chatelier's principle, super important for them, cat. Like insanely important. Okay, so anytime you increase something or decrease something, the formula is gonna shift. So for this example, we're decreasing carbon dioxide. Carbon dioxide is on the left side of our formula. So we're going to experience a left shift. That means that everything is gonna shift leftwards. We're gonna produce more of it because we want to balance things out. So that means that we're gonna actually end up producing more water. We're gonna shift left. And that means that all that hydrogen ions and HCO3 minus is gonna shift left to the H2CO3, that bicarbonate, or sorry, excuse me, that carbonic acid. And then we're gonna shift that even more left to our CO2 and H2O to compensate for that less carbon dioxide that we're having. Because we want to maintain in balance. Our body wants homeostasis. So in this little equation, when we decreased CO2, we shift it to the left. But when we shift to the left, that means that the stuff on the right is becoming less. Okay? It's becoming less. Anytime you shift a certain way, you're using up those materials in order to balance it. So we've got less H2CO3 or carbonic acid. And now we have less H plus ions and less bicarbonate, like HCO3 minus. The important part of this equation to understand is that H plus ions. H plus ions are dictating our acidity level, dictating our pH, right? If you took first your chem, you know that H plus and pH are related, right? The more H plus ions we have, the more acidic we are, the lower our pH. So think about it. If we shift it to the left to compensate for that lower amount of carbon dioxide, we're decreasing the amount of H plus ions, and therefore we are increasing our pH because we're becoming less acidic. We're becoming more basic. So therefore, when we have a faster respiratory rate, we have a higher amount of oxygen, a lower amount of carbon dioxide, and therefore we are increasing our pH, aka becoming more basic. So I hope you understood that. I'm gonna give you another one now, and you're gonna tell me how this shifts. Okay. So this one's easy to start off. What happens with our lower respiratory rate? If we breathe slower, tell me what's gonna happen to our equation and go piece by piece and explain it to me. So right now you should be talking to yourself. You're gonna sound crazy if you're on the train or if you're in your if you're walking your dog, people are gonna think you're crazy, but just do it. Okay, I'll give you the explanation now. So slow respiratory rate means less oxygen, more carbon dioxide. So what happens? We're putting a big up arrow beside our carbon dioxide. Okay, an up arrow beside our carbon dioxide, if it's on the left side of our equation, means a right shift. Right shift. We're gonna push stuff to the right, okay? Because we want to balance it out. Right now we have too much carbon dioxide. We want to spread the love, spread that material over to the right side of the equation to become balanced. Okay, so we're gonna shift to the right. That means we're gonna have more carbonic acid, we're gonna have more H plus ions, more HCO3 minus, or bicarbonate. Okay, so what's important here, what we care about, is those H plus ions. So those H plus ions, if it's becoming more, we're gonna lower our pH and become more acidic. Therefore, slower respiratory rate equals more acidic. Make sense? So now that you understand that, try to go back and work through the examples in your head of respiratory acidosis, what it's caused by, respiratory alkalosis, what that's caused by. What happens to your respiratory rate during metabolic acidosis? So that means that your acidosis is not being caused by your breathing rate, it's being caused by something else in your body. So your body, your blood is already acidic. What's gonna happen to your respiratory rate? And during metabolic alkalosis, what's gonna happen to your respiratory rate? Go through those four examples and see if you can work through them. Um, and if not, you definitely need to look up a video, you definitely need to do some content review, do some practice questions, because this should be easy peasy free marks on the MCAT because I guarantee you it's most likely gonna come gonna come up. Super high yield. Okay? Just understanding Le Chatelier's principle in general is essential. You will fail the MCAT if you don't understand it. Okay. Okay, a few more questions and we're done. These are a bit fun. Okay, so to cool off, dogs do what? Where they breathe with their mouths open, which evaporates the water inside the respiratory system. So if you have a dog here, a bit of a cheat code. And dogs pant, okay? And that's because while dogs have sweat glands, they're pretty limited and they don't work the same way that human sweat glands do to cool the body. So they rely primarily on panting. Okay. When the epiglottis is closed, food travels down what? Which leads to the stomach where digestion is continued. And this is down the esophagus. This is a bit of a sneak peek into a next episode coming up, maybe. Um, so keep that in mind because it's gonna be a repeat question. Okay, and I do have one more question for you. See if you can remember this. What is the principle that states that when a reaction is moved out of equilibrium, it will rebalance itself? Everyone, every one of you should be getting this correct. This is Le Chatelier's principle. Look it up if you don't understand it. It is super important. That's what the all of those questions regarding acidosis and alcoholosis, that's what that's based on. So I'm sorry if this episode was a bit slower than you're liking. Um, as always, you know, you can skip through things, and if something's too easy for you, just go ahead. But this is gonna help you streamline your content review, identify gaps, and identify strengths too. Identify a strength means that you don't have to really study it too much. Focus on the stuff that you're not as confident on, and that's how you're gonna maximize your score. Anyways, that was the last question. So I hope you enjoyed. I hope you learned something new, and if not, I hope you reinforced your current understanding. And as always, if you have any questions, corrections, or suggestions, please feel free to email me. And with that, I will pass the mic back to Slim Shady for a final message.

SPEAKER_03 30:20

Thanks, Isa. I learned a lot from this episode. If you guys also benefited from this podcast, please feel free to leave us a review as it helps us reach more students. And for all the listeners out there, you got this. But before I go, I just want to share something with y'all.

SPEAKER_04 30:40

Keep it real. That's right. Number nine. No one's ever regretted a tattoo.

SPEAKER_05 30:44

That's right.

SPEAKER_04 30:45

Number eight. With foreign markets volatile, now's a good time to invest in bombs. Number seven. OC Toy Story 3, the toys are back in town. Number six, always purchase music through authorized retailers. Number five. Don't get mixed up with drugs, games, or oil executives. Number four. The magic words. Please, thank you, and step on. Number three. Money doesn't buy happiness. It buys craziness happiness. Number two. If I sign something for you and I see it on eBay, when you go home, I'm gonna be under your bed. Don't waste your time watching this show.