Comprehensive Heart Anatomy, Physiology, and Electrolyte Balance Explained

All right. Well, I'm recording this anyway, so if anyone's a little bit late, they can always watch the

recording. But why don't we get started since it looks like almost everyone's here anyway. Um, welcome and thank you

for having your cameras up. This makes it so much more fun to do this. All right. Uh, you guys did really well on

the lab on the quiz uh last week. Um, almost I think the average score was like a 19.5 out of 20. So that's

awesome. Like almost everyone ended up getting an A on it. So I think almost everyone used two attempts, which is

perfectly fine. I think you've gotten a sense of how these questions get asked um and like how to answer them. Many of

going into like a healthcare related field, there's a lot of people going into nursing. And when you sit for your

nursing boards and take your nursing exams, the questions are going to look just like that. Um they're going to be

clinically based. There's going to be kind of a longish stem. there's going to be a lot of confusing possible answer

choices and so the more you get used to answering questions like this, the easier those nursing boards and exams

and medical school exams and everything else uh become. Uh so that's good practice. So great job on the quiz. Um

that was really good performance. A lot of you have also already done the lab quiz for this week. And so remember uh

more than one answer can be correct. Just read the question stem. It says right there as well more than pick all

of the correct statements. Um, and people are doing well on the lab. Um, as you know, you get only one shot on the

lab and so scores have dropped off a little bit, but I think the average right now is still like a 85 90%. So,

that's really good. Um, I some of you have checked in with me and just let me know how things are going and and you

mentioned that you watched the lab video a couple times and like took some notes and like had that image up while you

were uh doing the lab. That's I don't have a problem with that. like you can print it out, annotate it, do whatever

you want with that image. And then when you do the lab quiz, you were saying that you had it with you as a reference

and it made a really big difference. Like it it became easier to identify structures and all of that. Um there was

some confusion about the bones and going through it a couple times and labeling it made a big difference. So that's

great. Use whatever study aid you want. I I have no problem with that. Um so overall, great start to the year for

most of you. That's it's really good. Uh some of you have reached out to make appointments. Um, I was able to meet

with almost everyone except one person this morning. Uh, so if you want questions or whatever, just use that

scheduling tool in Moodle and happy to meet with you. Um, so that's all. Okay. So, for today there we're only meeting

today. There's no class Friday. Uh, and the only thing due this week, there's no quiz this week. There's only a lab uh

that's due this Friday. And most of you, some of you have already finished it. So, good job. Um, so we're going to

continue with the heart. um we're going to go into more detail about like the muscles and some of the physiology. And

so, you know, we've been trying to connect how the anatomy works uh with the actual physiology part of it. And so

far, what I've done is shown you how like where the SA node goes, where the AV node goes and and all of that. But

today, we're actually going to connect some of the physiology together with like the biochemical aspects of it. Like

what are the ions? How do they actually flow into the cells? how do how does like a more of a chemical signal turn

into an electrical signal? Uh where are these ions located and so on. So that part's actually really important. Um so

uh actually before we get there, let's talk about the muscle of the heart in a bit more detail. Um as we had just

started talking about uh in the last lecture uh the outermost part of the heart, this this envelope right out here

that encases the heart uh that's called the paricardium. There's technically two parts to it. There's a cirrus component

and a I'm sorry, a parietal component and a visceral component. But together, for my class, all you got to know is

that the outermost layer is called the paricardium. And the reason that's important is that that's kind of like

the bag that the heart sits in. And as the heart is beating, you don't want the heart to be hitting surrounding

structures. You also want to insulate the heart from those surrounding structures and decrease the friction as

it's moving around. So the paricardium creates that bag. Imagine it's just like a grocery bag. instead of it being

filled with air is filled with some a small amount of fluid. And so that fluid helps lubricate the muscle of the heart

and lets it move around without damaging it. The muscular portion of the heart itself, that's called the myioardium.

That's the most important part of the heart that gets damaged if there's like a heart attack. Uh and so that's that's

the part that you want to uh kind of be uh aware of when you have something called a myioardial eskeemia. And here

I'll put that spelling back in the chat so you have it. myioardial infarction equals heart attack. All right. So, uh

that's the that's the heart muscle that gets damaged. And obviously, that's the part of the muscle that is super

important because if that's damaged, the heart is unable to beat anymore. It's unable to generate the compress the

compressive forces it needs to push blood throughout the rest of the body. It's almost like part of your biceps was

damaged. What do you do? Well, you can't flex your arm anymore, right? If the muscle is damaged and not working, that

part of your arm isn't working anymore. And then the innermost part of the heart, that's called the endocardium. So

three layers, long story short, three layers. There's the paricardium, which is the outer part, myioardium, which is

the muscular part, and very thick, and the endocardium, which is the innermost part. And a question someone asked last

week is, well, why can't the heart survive off the blood that's flowing through it? And the reason is is that

this very innermost part of the heart which is exposed to blood does kind of survive, but the rest of this muscle

doesn't actually benefit from that internal flow. And that's why you actually need a circulation system for

the heart. There's no other efficient way to do it. All right. So this next part in your

notes, you want to write down that there's three types of muscle. And I'll tell you what they are first. The first

one we're going to talk about is skeletal muscle. Then we're going to talk about cardiac muscle and then we're

going to talk about smooth muscle. So how this works is that uh there's basically three types of muscle located

uh throughout the body. The kind of muscle that you have full control over. That's part of it's something called a

somatic nervous system. You'll learn about that next semester, but here's the spelling in case you want it for your

notes. Somatic nervous system. That's voluntary control. Spelled control wrong. Okay. So the sematic nervous

system is what you have voluntary control over and that's all skeletal muscle. So when you're thinking about

like kicking a ball, moving around and and like waving your hands, uh all of that's been controlled by skeletal

muscle. What makes skeletal muscle different than the other two types of muscle? There's a bunch of there's a

bunch of little things and and of course this is going to be like a short answer question on the midterm. Okay. So, one

thing that makes Ela muscle different is that it has one it has many nuclei in one cell. This whole thing you're

looking at here is one cell. And I'm going to flip to cardiac muscle real quick to show you the difference. So,

this is cardiac muscle. These are separate cells here. Okay. So in skeletal muscle all those

cells have been fused together into one long myofbral and inside that one giant cell are multiple nuclei. So one thing

I'm looking for is multi-ucleate. Skeletal cell skeletal muscle it's right here. Skeletal muscle is multi-ucleate.

And the other thing is that the cells tend to be very long because they've all been fused together.

So it makes them into really long fibers. And the third thing I care about is you

see how there's like this unique pattern in skeletal muscle. If you looked at under a microscope which you can see

here this is light microscope at 180 magnification you see that same exact pattern. That pattern those p the name

of that pattern those are called striations. So skeletal muscle is striated and that

unique pattern we'll talk about that in a few weeks I think almost a month from now we'll talk about that but there's a

reason for that pattern that goes to how the muscle actually works. We'll come back to that in in in a future lecture.

Okay. So let's talk about cardiac muscle. Cardiac muscle is different and this is what I'm looking for on the

test. Cardiac muscle is different than skeletal muscle because it tends to have only a single nucleus in a small cell.

However, like skeletal muscle, it's still striated. So, how is cardiac muscle same or

different than skeletal muscle? Cardiac muscle has a single nucleus. It's a much smaller cell, but it still has

striations. And you can see that pattern right here. You can still see that regular pattern.

And then finally, the third type of muscle, uh, oh, by the way, cardiac muscle where it's found, this is

obvious, it's found in the heart. Okay. Then you have smooth muscle. All right. So smooth muscle is found in a

bunch of places where you maybe you didn't know this. Uh, so smooth muscle is found in blood vessels and it helps

blood vessels kind of contract and constrict. That's actually really important because if you're if you have

a cut and you're bleeding, those muscles help constrict that muscle and will literally prevent you from bleeding to

death. So, that's one place, one important place is found. Smooth muscle is also found in the GI tract. It helps

like your intestines squeeze and push poop out. It's found in your lungs. It's found in your uh bladder and urinary

tract. It again, it helps you like squeeze your bladder and helps you pee. And it's also found in your reproductive

organs especially like the uterus which has a lot of smooth muscle very uh very strong smooth muscle in it. Uh so uh

smooth muscle is different than the other two types of muscle skeletal muscle and cardiac muscle and in some

ways it's similar. Here's here's here are the traits of smooth muscle. So it doesn't have the striations that makes

it different from the other two types of muscle. There's that pattern is gone in smooth

muscle. But like cardiac muscle, it has a single nucleus.

And like cardiac muscle, the cells tend to be small. Okay? So smooth muscle is different than

the other two types of muscle because it has no striations and it's like cardiac muscle and that has a single nucleus in

a small cell. The other aspect of this that I want you to remember is where these types of muscles are found.

Remember, skeletal muscle is found in like the named muscles that help you move around. You can give like the

biceps as an example. Cardiac muscle obviously found in the heart. Smooth muscle, the things I'm looking for, it's

found in blood vessel. It's found in the GI tract. It's found in the reproductive organs. And if you name a few others,

that could be worth a couple extra points. Okay,

you you don't need to know this. Um there's only a few things here which are kind of important. Uh so this is really

comparing cardiac muscle to skeletal muscle and there's really only one major thing I want you to know and that's the

blood supply. So someone had asked uh last week um yeah Taran that's a good good way to put it. You can say that

smooth muscle lines most of the internal cavities but I I'm specifically looking for blood vessels as well since that's

that's also a unique case for it. So yeah, Taran, that's a good way to put it if you happen to see that question on

the midterm. Okay. So the one big one other big thing I'm looking for with cardiac muscle, especially cardiac

muscle compared to the other two types of uh muscles is that the blood supply to the heart is very very extensive and

someone had asked this in class last week like uh how is the heart able to keep pumping over and over again and how

cockman doesn't get tired like skeletal muscle and there's a few reasons for it. One is because of the unique type of

muscle it is. There's a whole different muscle class called cardiac muscle uh that is found in the heart that's not

found elsewhere. Those fibers tend not to get tired because of how they're made. And the second aspect of it is

that it has lots of uh uh blood supply going to it. And so that rich blood supply prevents the heart from getting

tired because it's always bathed in nutrients and oxygen. Um, some of you may have heard about like aerobic versus

anorobic uh, circulation and metabolism. We're going to talk about that more in a later lecture, but the idea is that if

you're like running a mile and your muscles are getting really tired and they're starting to burn and like that

that burn you have after you exercise really hard or like play a sport or something, you've gone into anorobic

metabolism and it's the buildup of lactic acid that's causing that pain. That happens in skeletal muscle and it

keeps that muscle going sometimes because you can switch over to lactic uh acid metabolism. Uh the heart muscle

does not do that. All right. So there you don't have anorobic you don't you don't you should never have anorobic

metabolism with the heart because if you do that's a really bad place to be. That means you're not getting enough oxygen

to the heart and it's actually going to start dying in in that process. It's very oxygen sensitive.

All right. So, uh, we've also talked a little bit about this. We talked a little bit about a heart attack or

myocardial eskemia. And so, the a good example of that here is what is the name of this first major blood vessel that's

going down along the actually it's it's vessel number two. What's what's the name of this blood vessel in the heart?

Also known as the widowmaker. We covered this last week. Put it into chat if you know it. I'll

wait a couple seconds. Yeah. What does it stand for? Look at its position on the heart wall.

Yeah, Emma, good job. Um, it's the left anterior descending artery. Okay. And you know that because uh, well, there's

a couple reasons this is important. So, that's number two. Number two is the left anter descending artery. That is

the artery that supplies the left ventricle. And the left ventricle is what's pumping blood to the rest of the

body. And if there's a blockage in that artery like they're trying to show here, then your left ventricle is no longer

functional, which means you can't pump blood to the rest of the body, which means you're not getting circulation to

your brain. And that's a quick way to die. And so it's called the left anterior descending artery. It's on the

left side of the heart. It's anterior as in it's on the anterior side of the heart. and it descends, it goes down.

And so a heart attack is basically the buildup of plaque in that artery or any any of the major arteries in the heart

and it prevents blood from being able to pass through uh and supply oxygen and nutrients to that muscle. So that's

basically what heart attack is. It doesn't have to be plaque that causes it. By the way, plaque is like the stuff

it's similar to the stuff on your teeth. Um it comes from like fats and eating too many cheeseburgers and smoking. Um,

but it doesn't have to be plaque that causes that heart attack. It could be a clot. It could be a torn blood vessel

that's called a dissection. Um, it could be uh direct trauma to the blood vessel that causes it to bleed and prevents the

blood from making its way down to uh that part of the heart. Uh, Jackson, is the left ventricle more muscular than

the other parts of the heart? Absolutely it is. Um, I'd mentioned that last week. The left ventricle is maybe like a 3/4

of an inch thick and the right ventricle which only pumps to the lungs is much much thinner and the right and left

atria which only pump down to the ventricles are super thin. Um in fact in if you're doing like heart surgery in a

really young person you can almost see through parts of the atria and kind of see the blood flowing underneath it

which is kind of a scary experience. Okay. Uh so in a mioardial inffection also known as an MI or heart attack

there's a bunch of things that can happen if you survive it which nowadays more and more people do uh remember

what'll happen is that the dead muscle will turn into scar and scar in the body has no function the scar doesn't work

okay so like if you fall and skin your knee and like you get a scar on your skin that part of the skin isn't

resilient anymore it's not functional tissue if you get a really bad burn and you lose some muscle in that burn that

scar scar formation over that area that muscle is not functional. The same thing is true in the heart. If you have a

heart attack or mioardial infaction and you form a bunch of scar that part of the heart muscle is no longer

functional. So there's a few things that can happen depending on where that's happened. Um you can rearrange some of

that muscle, but it means that the heart is is not at 100% function anymore. And that's what leads to congestive heart

failure. And of course, abbreviation for that is CHF. All right. So, if you know someone who's

had a really bad heart attack and they've survived, then one of the things that can happen is that their heart

functions no longer as effective. They're not pumping blood out of the heart effectively to the rest of the

body and it starts leading to congestion. That's called congestive heart failure. It's because of a

decrease in heart output. The other thing that can happen is that the damage happens right around like the conductive

pathways like the SA node, the AV node, the bundle or the perkingi fibers that leads to a problem in electrical

transmission and that can lead to one of those horrible looking arhythmias that we talked about uh last week.

Okay, so let's get into electrophysiology. This is really important and there's I'm

going to show this to you a bunch of different ways. Um, but uh maybe this is the easiest way to put this in your

notes. Uh, what I want you to pay attention to is the size of the letter. All right. Uh, give me one second.

There's a lot of noise outside. Let me close the door. Okay. So, all right. The size of the

letters actually is maybe the easiest way to understand this. Now, I'll show you a different version of this over

here. Maybe this some of you may find this easier. And there's actually a table that we're going to go through as

well. So if this is how you learn, wait for this. If this is how you learn, wait for this. And if you are more graphical

in nature, like I like seeing it like this. If this works for you, write this down. Um, okay. So here's what you're

looking at. You're looking at a bunch of different ions or elements in this case. K is potassium, Cl is chloride, Na is

sodium. And if you've seen the periodic table of elements, then you already know this. Um, and and for those of you who

don't remember or haven't seen it, I'll put in chat real quick. So, Ka is potassium, Na is sodium, and Cl is

chloride. And you can see that there's a plus or a minus next to it, making those ions. All right? So, potassium is

positively charged, sodium is positively charged, chloride is negatively charged. Um, and and again, most of you probably

already seen this in like high school chemistry. Um, all right. So the big letters mean that they're in high

concentration. The the small letters mean that they're low in concentration. And what this box is supposed to be is a

cell. Okay. So what this is trying to say and this is this is how um cell transmission, electrical potentials,

neurons, cardiac muscle, skeletal muscle, this is how they all work. All right? And having this concentration

gradient is really important. So what's happening is that the cell is very high in potassium concentration.

And if that's all you remember, then you'll get everything else right because chloride and sodium are low in

concentration. Now, I have I have a bunch of stupid ways of remembering things. And the way I do this is I just

remember potassium is in like so confused and think P is phosphate.

Um, so you can remember pin or you can remember like kin, like kinship, like friends or cousins. All right. But I

that is it's a dumb way to do it, but it works for me and I never get it wrong when I do it that way. Um, so if you

remember PIN or KIN or whatever, that's a quick easy way to get this question right. This tends to be a multiple

choice question on on a midterm. Um, but I don't know, maybe I'll turn it into a short answer drawing or something this

year. But if you remember potassium is in, you'll remember that chloride and sodium are outside the cell in higher

concentrations. uh don't worry about organic ions. We're going to cover that in a separate area. All right. So, the

reason this is important and is because this is how these ions flow out and cause a change in the electrical current

in the cell in the electrical potential of a cell. If potassium is flowing out, then it's going to make the

concentration of chloride a little bit higher. Especially if chloride is happening to move in at the same time.

So, as potassium flows out, the cell becomes less positive. As chloride continues to move in, the cell becomes

from less positive to more negative. If you have vice versa, if you have sodium flowing in, then the cell becomes more

and more positive, especially while potassium is flowing out at the same time.

You need a way to balance some of the charge. The other thing that happens is that say that you have a cell um that

has just been fully discharged and you have a bunch of potassium and sodium and chloride outside. How how do you get

this back into balance? Well, what you have are ion channels and sometimes there's a bunch of different ion

channels, but basically what happens is that some of them are selective specifically for sodium and and

potassium. And what'll happen is that the potassium will will selectively flow into the cell against its concentration

gradient, right? Because what's happening is that potassium is really low outside. So you actually need a pump

to pump it back into the cell. And sodium is really low inside the cell and really high outside the cell. So you

need a pump that pumps the sodium out. So what happens is that you will have a pump in the cell that uses energy. It

uses ATP to make that concentration come back and it'll pump the potassium back in and it'll pump the sodium back out.

And what'll happen is that you'll get back to this default state allowing the cell ready to get uh its next firing

ready. Like if it's a neuron, it'll be ready to fire again. If it's a heart muscle, it be ready to beat again. So

that gives you a sense about how fast this works, right? This is measured at the millisecond level.

All right? If this is how you learn, then just make a bar graph. And it's it's exactly the same stuff. I there's a

bunch of extra ions here. Don't worry about them. The ones I really care about for this class right now are sodium,

potassium, and chloride. Um, and so basically intracellular fluid, that's the fluid that's inside the cell. Plasma

uh is what is bathing uh the surrounding tissues along with interstatial fluid. And you'll notice there's a difference

between these two. We'll learn about them when we talk about blood. Um but for our purposes right now you can treat

plasma and interstitial fluid as being similar to each other. Um and then just com just contrast that to intracellular

fluid. And one more time sodium is really low in concentration. Potassium really high in concentration. And then

where's your friend chloride? Here it is. Uh chloride is really low in concentration inside the cell. Don't

worry about the mill equivalents. Okay. So you're going to look at this and be like, "Oh my god, this is a lot.

I hate tables." And I I hear you. And the reason why tables are painful is cuz they have a ton of information in them.

And it's a great way to communicate that information efficiently. So I'll tell you right now, this is something that's

extremely important. Um this is important not just for patient care. Uh so you you got to know this if you're

going to any of the clinical sciences, even if you're doing like exercise therapy or you're uh going to like uh

physical education or something. This is super important for everybody that's got a healthcare bent. Um, it's also

important for life. So, it applies to everyone in class. Um, basically, these are some of the ions that make a

gigantic difference in how the body's chemistry works. And if these ions are out of balance, like sodium, potassium,

calcium, magnesium, phosphate, or chloride. If they're out of balance, it leads to all sorts of badness. Like you

start feeling sick very quickly. And if they're still not fixed, it leads to death. really fast. Uh some of these

like calcium can kill you within like minutes if it's really screwed up. Uh others like potassium, where is it? If

potassium gets uh screwed up really fast, it can lead to a fatal rhythmia. And trying to save someone from that is

like next to impossible. So some of these can kill you super fast. Others really important in pregnancy. If you

want to slow down or speed up how fast you're contracting during childirth, magnesium plays a big difference in

that. Um, others like phosphate play a really big difference in bone chemistry. If your phosphate levels and calcium

levels are off, you get osteoporosis and your bones can break really easily. Sodium plays a role in how thirsty we

are along with chloride. Like sodium chloride is t is literally table salt. So let's go through them because I

actually want you to know a large parts of this table. I'll be very specific about what I want you to know. So, if

you're if you're writing your notes out, write out all of these going across as the first column in your table.

And then we're going to go through what happens if you have too much, which means hyper, or if you have too little,

which is hypo. And we're going to do that for most of these. Okay. So, hyperatriia. Natriia means

salt mean specifically means sodium. So if you have hyperatriia, you have too much sodium. Now it wear is

really important. Okay, it's not too much sodium in your skin or your like your right foot. Okay, this hyponetriia

is specifically having too much sodium in your blood. So you've got hyperatriia which is too

much sodium and hyponetriia which is too little sodium. And let's define all the others while we're at it. Okay. So for

potassium it's hyperclimia or hypocalemia. Too much or too little potassium. Calcium's easy. Hypercalcemia

or hypocalcemia. Magnesium hyper or hypom magnesmia. Phosphate is hyper hypo phosphatemia

and chloride is also easy hyper hypo chlormia. It's a lot in one table but you will see

this every day you practice. All right. And if you don't know this you will kill someone. Like if you fail to recognize

abnormalities in this or fail to treat it properly or fail to alert someone about it or you yourself don't know that

this is happening to you, bad things will happen. Okay. So let's go through let's go

through them and I'll like I said I will keep it simple so that I'm you're really only learning like the key essentials

for each of these. There's a lot of detail that comes in this table which you don't really have to know. Like for

example we are uh we are not going to cover treatments. Okay, like this is not a clinical medicine class, so we're not

going to really go over treatments. Um, Kaye, hyper means too much. And Haley, uh, this is too much or too little in

the blood for each of these conditions. So, if you're talking about hyperclamia, that's too much potassium in the blood.

Okay. So, let's go into like some generic signs or symptoms of each of these. So, if you have too much salt in

your blood, what does that mean? That means in terms of ratios, you don't have enough water in your plasma. Plasma is

part of blood. So if you have too much salt, you don't have by proportion you don't have enough water. So if you don't

have enough water in your blood, what are you going to feel? You're going to feel thirsty, right? Because you're

going to feel really dry because you because there's too much salt, not enough water. So all that is all the

major sign of that is thirst. That's the only thing I want you to know. And that's easy if you think about it. If

you have too if you eat too much salt, what are you going to drink afterwards? A lot of water because you're going to

be really thirsty. That's why drinking ocean water doesn't work. It's got too much salt. You can't

keep up with getting enough water in it uh to balance it out. So, a cause of being thirsty is simply being

dehydrated. And that's the only thing I want you to know. So, if you have too much salt in your

body, that means you don't have enough water to balance it out. If you don't have enough water, that makes you

thirsty. And if you don't have enough water, you're dehydrated. Okay, so this one's not so bad. You can

think about think this through and and figure it out. So, hyperetriia, not bad. Okay, hyponetriia is the opposite. You

have way too much water and not enough salt in your body. And remember the cell, right? Remember what was inside

the cell? A lot of potassium and very, very little sodium. So if you have even less sodium outside the cell, then what

little sodium there is in the cell won't want to stay in it anymore and it'll want to leave. And that's really bad

because you need a basic amount of sodium in the cell to maintain some like pressure. It's called hydrostatic

pressure and and maintain tension on the cell walls. What happens if you have too little sodium

because your water levels are too high is that it makes cells start to explode. And we see that as the brain because the

brain's really sensitive to this. So we see it as the brain not functioning the way it should. So you can call this

anything you want. You can call it disturbed CNS function, central nervous system function. You can call it

confusion, hallucinations, convulsions which is like seizures or coma or just call it like abnormal brain chemistry.

Whatever you want to write for that related to the brain, I will accept as an answer. Okay. The key is that the

brain is dysfunction. Write it any way you want. Seizures is simple. Okay. Okay. So, hyponetriia, low sodium in the

blood can lead to seizures. This is I've seen this. This is this is horrible and it's really really hard to

fix because you can't just pump them full of sodium because what'll happen is that it'll go into the cells really fast

and they're all like shrunk and not shrunken and like not able to expand quickly and that will make the cells

explode. So you actually have to do this really slowly, but you're balancing it against their brain literally dying. So

this is a hard place to be. All right, potassium it gets more serious. As if that wasn't as if your brain exploding

wasn't bad enough, potassium gets more serious. Uh so uh if you have hyperlamia, that means you have way too

much potassium going into the cells. And think about like I said earlier that these ion balances are really important

for like the heart. This is how heart function works. So if you have too much potassium going into the cell, what's

that going to do to how your heart conducts electricity? It's going to start causing problems with it. So it

leads to arrhythmias like aphib, VTAC, VIB. We talked about that last week.

Don't worry too much about the causes. We're going to cover this next semester, but kidney failure is a big is a big

reason why most of the rest of these happen. Problems with the kidney lead to issues with almost all of these other

ion concentrations. And we'll keep it simple. If you have hypoclamia, you also still get

arythmias. It's a different kind. It's the heart not working as well. And that leads to its own different types of

arhythmias. So if you write down arithmia for both hyper and hypocclamia I'll accept it. It's a just remember in

the back of your head it's a simplification and when you're learning this again later in a professional

school just learn that additional detail hypercalcemia. So calcium is really important because it leads to squeezing

of the heart and it's an important ion that helps the heart contract. You can remember that as calcium

contracts. So cal and not just the heart but all muscle. So if you have too much calcium,

there's a whole bunch of different symptoms that happen and they're all kind of related to each other. And here

I'll put this in chat cuz it's a lot. Stones, bones, groans, and psychiatric overtones.

And if you remember just that for both hyper and hypocalcemia, that's good enough. So what do I mean by

this? Stones means kidney stones. If you have too much calcium, you tend to get kidney stones.

In fact, most kidney stones are made of calcium. Bones literally refers to the bones in

your body. And if you have too much calcium, it leads to the bones having high density, which is not a good thing.

And if you have too little calcium, well, this is the part that you've heard about before. That's osteoporosis

or literally holy bone syndrome. It makes the bones weak. Happens as you get older, especially in

women after menopause. And then so that's stones. That's bones. Grohones means pain. Everything hurts.

You get cramps. You get seizures. Your intestines hurt. And I know it says that specifically for

hypocalcemia, but it actually happens in both sides. Hypercalcemia and hypocalcemia.

That's why I'm grouping them together. And then psychiatric overtones, you literally start to have like

hallucinations and feel like you're going crazy. Your brain doesn't work the way it's supposed to on both ends, both

sides of this. Too much and too little. So you can see I've tried to make this a little bit easier. Sodium is the only

one where we broke it apart. potassium on both sides. It was arhythmias. Calcium on both sides, stones, bones,

groans, and psychiatric overtones. So remember remember what I just put in chat. That's kind of what I'm looking

for. That is what I'm looking for. If you see this on a midterm, magnesium, we'll keep this simple as

well. We'll refer we'll keep uh we'll think of magnesium as only uh only as uh balancing muscle function. That's what I

would write next to magnesium. Next to phosphate, I would write down phosphate works with calcium balance.

We're going to cover both of those in a later lecture. Some of it's actually next semester.

And chloride works with sodium. That's all you got to know for chloride. All right. All right. So, we've gone

from this really intimidating looking table to a simplification, which is actually pretty good for a clinical

setting. If you're going into like intensive care medicine, if you're going to be like an ICU nurse or an ICU

physician, you will learn this in even more detail. And those details will be really important. But for general

day-to-day stuff, this is good enough for us. Okay? And remember, the cause of most of

these is basically kidney damage or kidney failure. So if you happen to see a blank table on

the midterm and it's labeled as uh yeah, Jackson, that's correct. And it's labeled with sodium, potassium, calcium,

magnesium, phosphate, and chloride. I'll ask you to identify the disorders. I'll I'll ask you for maybe a symptom or

finding or condition that's related to it. and I'll ask you for a cause and that's it. And so it should be pretty

straightforward based off we just covered hyper and hypo for each of them. The signs thirst or CNS dysfunction for

sodium. Potassium is cardiac arhythmias. Calcium with stones bones grow psychiatric overtones. Magnesium is

related to muscle function. Phosphate is related to calcium concentration. And chloride is related to sodium

concentration. That's good enough for the signs and symptoms. And for causes, dehydration is or too much fluid is good

enough for hyper hyponetriia. And for the rest of them, kidney failure works. Okay,

so I've got 15 minutes left. Let's cover how action potentials work and how they're built. So we've talked about

sodium, we've talked about calcium, and we've talked about potassium. Don't confuse calcium with chloride. All

right. So what happens is that when the heart is resting that it has a if you measure its electrical potential it'll

turn out to be pretty negative at -90 molts. Volts are like the pressure to move current along.

So - 90 molts means that there's not much pressure at all on the heart to like to generate a current and to

contract. So that's when it's resting. Now what happens is that in that very first step you get a bunch of sodium

entering into the cell. What is the charge of sodium? It's positive. So what will happen to the negative 90 molts?

It'll become much more positive and it has this big spike that goes all the way up to 30. In fact, hey, doesn't that

kind of look like a QRS complex, right? It's like the beginning of the It's like the Q or the R part, right? The part

that spikes up. um that's not literally what it is, but it's a good way to remember that um there's like a big

spike as positive charge enters the heart. So in number one, sodium enters the heart and it becomes really

positive. And then in the second part, calcium starts to enter the heart. And so that's this part over here. Calcium

is entering the heart. And we'll cover this in um Monday's lecture next week. Calcium is entering the heart because

it's helping the muscle to actually contract. it works with ATP to cause that muscle to ratchet along and do the

actual contraction. So that's why calcium is entering into the heart. And during this part, this is something

called the absolute refractory period. The absolute refractory period means that when this is going on, you cannot

excite the heart anymore. You can't have it beat again because it's in the middle of a beat and it can't be stopped or

started. It's just going to continue what it started. All right. So, this is also

this is another way to think of it is that this is an all or nothing phase and it's committed to being allin right now.

And then the concentrations start to get reversed. Calcium starts to flow out of the cell. Sodium starts to flow out of

the cell. um and potassium starts to flow out of the cell to get the uh charges balanced back out and you enter

something called the relative refractory period. And notice the time, it's about 200 milliseconds that that's happened.

I'm not going to test you on the time. Um but it's really fast. And so during this relative period, the orange part,

if you had a really powerful signal, like if you were like running away from a lion and you had to like get as much

energy as you can to your heart, your heart could technically beat again if it had a strong enough signal. This is a

really fast heartbeat if that's really happening. Like this is not really compatible with life. Um, but that's the

fastest you could get around 200 milliseconds. No one no one's heart is going to beat uh 300 times a minute,

right? 5* 60 is 300, but that I mean no one's going to beat that fast. But it tells you that like

that's the absolute upper limit in terms of how fast your heart can beat. All right? Um or like how a muscle can

can contract because this is not just heart muscle. This is also skeletal muscle and smooth muscle as well. All

right. So this is this is what that what an actual potential looks like. And you have thousands, hundreds of thousands,

maybe millions of these inside the Pwave, the QRS complex, and the T-wave. Like those waves are literally built up

of these action potentials. They're all like summed together to make that curve. Okay? So that's really what's building

that larger wave that we see. It's all of these hard cells working together with all their little action

potentials summing up, adding up to build that larger wave that we see. So this is the representation of millions

of heart muscle fibers beating when they do in different parts of the heart. Each of them having their own little action

potential. So uh Zane, this this whole thing is called an action potential. That's what you're looking at here. And

this is for all muscle Jackson, heart muscle, skeletal muscle, smooth muscle, all of it. All muscle does this.

So let's do a quick review about how the action potential how the uh EKG waves are actually made. So we talked about

the SA node. This should be reviewed, right? So the SA node is what starts it. That's the pacemaker node. And that's

when you see the beginning of that Pwave and then the actual Pwave is when that action potential spreads out to the

different atria, the right and left atria. And that's when you see the heart muscle contracting with all its little

action potentials being summed into the Pwave. And that's when you see the Pwave bump. Okay? So, so far this should be

straightforward. You should know this and you already know what's coming next. You have that little bit of a delay. So,

here's a number again. You have the 100 millisecond delay and that's because of the AV bundle and that's called the PR

interval. Here it is right here. PR interval. Okay. So, that's the brief delay. And

what's happening? Well, it's showing you here, right? you've just finished contracting the right and left atria and

that uh you have that brief delay to allow blood to be pumped into the right and left ventricle and then the impulse

travels along they're calling this the interventricular septum remember I taught you septum that's the muscle

interventricular means just between the ventricles and remember what it's actually traveling in the name of those

fibers was called what first person in chat what was that bundle of fibers called

right there. Nope. No, not not not forking. It's the bundle. Right, Jackson. Good, Jackson. You nailed it,

Jackson. Email me bundle. Fine. I kind of gave that away. So, it goes down the bundle in the

septum and you see that as the beginning of the Qwave here. And then you get to this part of the heart. Who's ready with

that answer? Yes, Anukica, good job. Email me, please. Um,

all right. I I'll give it to everyone here. Okay. Uh, here, I'll just take a screenshot. Good job. Okay. Um, it so it

goes down to the apex of the heart and then obviously it travels up the perkingi fibers. Um and and that's where

you see the rest of the QRS complex uh shooting up the ventricles and and and this this diagram does a really nice job

showing that and then you know the rest of this you get you've had atrial contraction and then relaxation in the

curos complex and now we got to get to ventricular relaxation um which I I just I just took it out because you already

know that ventricular relaxation will be the T-wave. Okay. Um I thought this was pretty good. This shows you the

breakdown of the EKG. Uh you already know this. So uh again you know the Pwave, you know the QRS

complex, you know the T-wave. Remember we talked about the ST interval and specifically talked about like an ST

elevation. Remember that was STEMI. That was ST elevated myocardial infarction. And what blood vessel was that again?

That was the L also known as the widowmaker that was affected. Right? So STEMIS immediate emergency. drop what

you're doing and get that patient to a Kath lab, right? If you call 911 and like you if you know what's going on,

you're like, I've got a STEMI, that ambulance is flying to your house and flying to the hospital as fast as I can.

Uh remember the PR interval that was 100 milliseconds and that's because of the AV node. So if I happen to ask this

question as an essay based question and I say tell me everything you know about the EKG, which is literally what the

question would be, like tell me everything you know. These are some of the details I'm looking for. Tell me

what the Pwave is. Tell me about the QRS complex. Tell me about the T-wave. Tell me about the PR interval and how long it

is and what makes it. Tell me about the ST interval and give me an example like ST elevation or ST depression and how

that correlates to a heart attack. Tell me what makes the EKG. So tell me about the SA node, AV node, the bundle, and

the perkini fibers. Right? That's what I'm looking for. Fill the page. If it's if you got two sentences, then write two

sentences. But if you have like a half a page for this one question and you write down a sentence, you're not getting full

credit for it, right? I'm looking for more. So this is where details count. This is where it this is what makes the

test hard, right? And intimidating. It's very much show me what you know. And if you've been coming to class and you're

like, "Yeah, this is like the third time I'm seeing it. I kind of get it." And then you review your notes, you're going

to kill it on the exam. You're going to be just fine. Okay. Um and then there's literally one

or two things left. Um, and then we're actually done with this lecture. Uh, so two things I want you to know. There's

something called the parasympathetic nervous system and something called the sympathetic nervous system. You'll learn

a lot more about this next semester, but just basics. Both of these are how the brain controls the heart. Okay? So parah

and sympathetic, parasympathetic and sympathetic come from the brain. And this is how the brain is regulating the

heartbeat. So if you like see a lion then your brain is going to analyze that and it's going to activate the

sympathetic nervous system which will speed things up. So sympathetic is a general rule speeds things up. That's

how I remember it. Parasympathetic does the opposite. It slows things down. We'll get into the

details next semester. Okay. Who knows what this is? This is not

worth any points. You You've seen this. Who knows what this is? What do you have here?

And what do you have here? And what do you have here? What was that called? Because you still have a QRS and you

still have a T-wave. So, you have a full EKG pattern, but you have Good job, Anukica. You have a bunch of extra

P waves. Okay. All right. This one is worth a few points. What's this? You see

a wave you recognize. You see a wave you recognize. And you see a wave you recognize. So, you have a full EKG

pattern with no duplicates. It's not VTEC. It's not a heart attack either because

you don't actually see an ST elevation. It's not VIB either. I'll show you that. One person got it right.

Ryan, good job. That is tacicardia. It's tachicardia. And you know that because you have way too many of these

patterns in a single EKG tracing. There's more here than there should be and you have the full pattern. You're

not missing anything and you don't have any extras here. So it's not a it's not VIB and you since you'd have a Pwave and

a T-wave, it's not VTAC. So this is simply tacicardia meaning fast heartbeat. And the correct spelling is

this. It's simply tac cardia. This

you don't recognize anything here. These are not P waves or T- waves and there's no QRS complex and it's a really fast

rhythm. This is VIB. Mason, good job. Yep. I didn't show VTAC uh but remember VTAC would simply be uh this

only QS complexes like that. And remember, VIB and VTAC not compatible with life. Without CPR, you're toast.

All right. And very last slide and you guys are out of here. Um, this is this shows what happens if you have aphib. It

forms clot in the left atrium usually. And that clot can go into the ventricle, up the aorta, up through what vessel was

that? Oh, this could be worth a few points. What is this blood vessel?

Nailed it. That is the left common corateed artery on its way to Yep. Joseph and Ryan, good job. That's on its

way to the brain. And where is that clot going? It's going to the brain to cause a stroke. All right, I'm going to stop

here. Uh we'll continue more with the heart. uh next Monday. Remember this Friday you have a lab that's due. We are

not meeting uh Friday. There's no class on Friday. And if anyone needs any help about anything or wants to ask

questions, I'll stick around right now. Feel free to ask me anything you want. Otherwise, I'll post this recording

online uh probably later today. All right. See you guys soon. Thanks for having your cameras on.

Feel free to unmute or just put in chat if you guys have a question about anything.