If you're taking anatomy [music] and physiology 1 this semester 2026, you are in luck because I organized biology am going to teach [music] through the entire course in this fall semester. So this is lecture one and as you progress through this course to the different lectures, we'll have the topics on [music] the top left. What I would do if I were you is compare these topics to the learning objectives your [music] Instructors have given you. Hopefully we'll teach them a little more fun and interactive. Hey everybody, Organized Biology [music] here where we make difficult biology
concepts simple. And today in lecture one, our first one, it's going to be the best one because it's number one, pun not intended. We're going to talk about four main topics. We're going to talk about what the heck is this course in general. Then we're going to go through 10 core concepts of A&P that I have developed that will help you understand the entire course. From there, we're going to talk about two specific topics within A&P, which is the levels of organization, kind of the hierarchy of structures we'll be talking about, and then homeostasis and
the positive and negative feedback loop. So, stick around for the entire time and you will learn a lot about the intro to P. So, let's get started. First, what is anatomy and physiology? Simply put, I Want you to replace these words with structure for anatomy and then function for physiology because all&p is is looking at the structures and functions of the human body. So if you look at say the organ of the heart, we're going to be looking at the structures of the heart, the epicardium, the mioardium, and then we're going to be talking about
basically what do those things do? How do they function? So structure is typically asking the question like what Is the structure? what does it look like? Defining features of it. But then this is going to be more the how or the why. Why does the heart function like that? How does the heart contract so many times every minute? So when we're thinking about these structures and functions, we need to understand that the structure will always fit or basically inform you about the function itself. So, as an example, the skin, the top layer of your skin
is called the Epidmis, and it is going to be made of a lot of cells. The basic unit of the body, and they're going to be stacked. So, basically, all these cells are stacked, stacked, stacked, stacked, stacked, all on top of each other. They're called stratified, so layered squamus flat cells. And then all the other tissues of your body, like your muscles and your the rest of your skin really, as well as your bones are all underneath it. So, Why do you think we have these structures of flat cells basically padded on top of each
other covering the rest of your body? Well, you could guess that the structure of the skin, the layered nature, the tough nature of it is going to be for protection, right? We're trying to protect all these underlying tissues. So, the structure of the body fits the function of the body. Does that make sense? Drop in the comments below what other structures of The human body can kind of tell you about the function of them. So think of like the eye, the hair, the the muscles. All right. Okay. So we're going to start with that. A&P
is just structure and function. And fun fact, that is my first uh core concept of&p is structure fits function. Structure fits function. What I like to tell my students is to think of themselves as like kindergarteners. Like you know how kindergarters they look at something and they're just like, "Oh, it's a gold lamp or it's it does this, right?" They're very descriptive about whatever they see. I know my young son is very much like that already, too. Um, but I want you to think like a kindergartener. Look at the structures that you're learning about first
and then try to infer maybe some of the functions based on how it looks because the structure will always tell you about the function. Now the second one I want you to know about A&P probably the most Important concept is going to be homeostasis. That's the second core concept of A&P. Now homeostasis is a cool term that literally translates to similar standing. So basically think of your body. You have a lot of conditions of your body that have to stay relatively constant over time to keep you alive. One such thing we could say would be
uh blood pressure. So your blood pressure has to stay pretty constant over time. If it drops too low, You would actually die pretty quickly. If it gets too high, you could also have some complications. So blood pressure needs to be in this happy homeostatic set point range where your body can optimally uh uh function. Right? Now other things could be like body temperature, right? So you need to keep your body temperature in optimal condition around 97 to 99 degrees Fahrenheit at any given point because your body operates best at that. So what Your body will
do is adjust its functions to try to keep these things steady. Okay. So let me give you a great example of that with my third core concept of A&P. This is going to be called the squeaky wheel gets the grease. squeaky wheel gets the grease. This may sound weird, so let me tell you a story quick. Let's say you're riding your bike and you hear that back wheel starting to squeak and squeak and squeak and it's really annoying you. So, you Decide to go down to your local hardware store on your own time and pay
some money, buy that WD40, that grease, and then obviously spray it on that wheel. Well, what you just did was sacrifice some of your resources, right? your money to try and get this WD40 to fix the biggest problem at hand, which was that squeaky wheel. So, you sacrificed your resources to fix something that's more important at that moment in time, right? Same thing with your body. Have You ever gotten really warm before? Have you gone outside on a summer's day, if you don't live in Alaska, uh, and you just started like sweating like crazy and
you're just drenched and your shirt's sticking to you? It's really uncomfortable. Well, why is your body doing that? Well, when you are sweating, right? What is your body squeaking out of you, right? What what is it leaking out of you? Sweat water, right? Well, is there a problem with That? Yes. Because fun fact, blood volume or basically fluid volume of your body is also a homeostatic set point. You need to keep the fluid of your body inside your body pretty constant over time. But what are you doing to that fluid volume when you're sweating? Well,
obviously you are decreasing the fluid in your body. Why? Well, because when you put fluid on the top of your skin, that water evaporates and takes some of your heat with it. So, by taking away Your heat, what do you get? Well, you cool off. So by sweating you're sacrificing fluid for the sake of maintaining your body temperature. Maintaining body temperature. Does that make sense? So your body in a way has a hierarchy of homeostatic set points where it says, "Hey, if this one's off, we're going to fix that one like nine times out of
10 at potentially the expense of another one." A great example is also blood Pressure. If you like say give blood, you lose blood volume. You lose blood pressure. Well, what may happen? You may actually go unconscious. I did that at one point when I gave blood. Don't let that scare you. I think you should give blood. It's a really good thing to do for society. But by losing my fluid volume, I lost blood pressure. What did my brain decide to do? It decided, hey, there's not enough blood getting to my brain. So therefore, I am
going to cut Off your consciousness. So I fell fell over, right? Well, when I if you can see this, right? When I fell over, I was horizontal. Yes. And my heart is now pumping to my head like this rather than like this. So, my body sacrificed my consciousness to get blood to my brain a little easier because now we're not fighting against what? We're not fighting against gravity. So your body considered blood pressure a more important homeostatic Set point variable than your consciousness essentially right so it sacrificed your consciousness so you could get blood to
your brain isn't that fascinating that I think that's just so cool how your body can kind of tweak things uh to keep yourself in homeostasis so these two obviously kind of go hand in hand awesome so let's move on if you have any questions please drop them in the comments below and if you haven't already just subscribe to the Channel like the video really appreciate you guys' support. It's a joy to be able to do this, guys. Okay, number four. Let's keep rolling. Got to get through these. Number four is going to be location, location,
location. So, I just write location times three. That's something that real estate agents say, right? Oh, the value of the property is based upon specifically where the property is located. So, location really, really, really matters in Anatomy and physiology. you need to know what specific location in the body we're talking about in order to understand how the function is going to happen. So, a great example I like to give my students is let's say um you eat some food. Where is the food now? So, you just ate some food. Let's let me see if I
can do a magic trick. Right, that was pathetic. Uh so, where is that marker? Where is the food now? Is it inside or outside of my body? Technically, it's still outside of my body, right? still outside of your body. What you say? But you eat it. It's now inside your body, right? No, no, no. Let's think about this. What if you took an indigestible string, something that will always be there, a string so long, 30 ft long, and you decide to swallow it, right? Swallow. And the string goes down, moves down in your stomach, through
your well, esophagus to stomach, right? And then it goes to the small Intestine, large intest, and then it comes out your butt. Did the string ever go inside your body? No. It stayed outside because the hollow tube of your intestines, I'll just show it as this. This hollow tube where that food just went is technically outside of your body the whole way because it's continuous with the outside environment. So the question is when does the food get inside your body? Well, that happens when the bloodstream right next to this Lining receives that food or the
nutrients from the food. So, let's say you digest the food and you have it outside your body, but then the cells lining your intestines decide to throw it to a different location, location, location. So, now we've got nutrients in the bloodstream that is considered inside your body. And from there my fifth core concept which is blood is a river of life comes into play. Blood is a river Of life. I want you to write that blood is a river of life. And I want you to also write and it goes everywhere. And it goes everywhere.
Basically everywhere. Okay? There's always a caveat, right? So when I mean everywhere, it means it goes to every single cell of your body besides your cornea and the epidermis of your skin. Don't worry about it. It goes to every cell of your body, the functional unit of your body, which are the cells. Fun Fact, you have 30 trillion of those cells. And if you are doing something, it is because your cells, the very livable units of your body are doing it for you. So here's the thing. If we just got nutrients to the blood and
the blood reaches all of those cells, right? So here are the cells and they need to have some glucose and some nutrients in order to survive. Are the nutrients inside your cells yet? No. But the blood is carrying it around To these cells. And so are the cells receiving these nutrients? Yes. But it has to come out of the blood and go into your cells. Now, so when we're talking about locations in the body, especially with physiology, the function of your body, you need to know, hey, is it technically outside of your body? Is it
in the bloodstream? Is it in the interstitial space, which is this interstatial fluid right here? Or is it intracellular? Is it inside the cells Themselves? Now, depending on where that is at, it's going to have a very big implication as to how we can use it. Because notice, if we didn't use this, right, where would it end up? Those nutrients would end up out of your body as poop essentially. Yes. So my sixth core concept is very simply use it or lose it. Use it or lose it. Great example of this obviously is nutrients in
the intestines. If we don't absorb them, bring them into the blood, they Are going to get excreted out of the body. But another example would be muscle atrophy, right? And you guys have probably experienced this before at some point in your life, but muscle atrophy is basically when you don't use a muscle very much. you don't put pressure and force on it, it'll actually get weaker. It will lose its size and lose its strength. The body is very much like that. The more you use a tissue, like your brain, your muscles, etc., the more It
will get stronger, but the less you use it, the weaker and weaker it will get. Awesome. So, those are six core concepts that are really important, but I still have four more. All right. Now, number seven. I want you to always, always, always remember that words matter in anatomy and physiology. Why is that? Well, because you're going to get these crazy words in this class. One of them, my favorite, is endocchondrial ocification. Endocchondrial oification, Right? And when you look at that word, you get scared and it makes you sound smart if you know what it
is to your family. So, you're welcome for this. But it, if you break the word down, the words will tell you what it means. Endo as an example means into, right? So something into a structure. Condraal refers to a structure called cartilage. Okay? It's found kind of padding your bones also in your rib cage. And then oification translates to bone growth or Bone development. So what is endocchondification? Well, it's bone growth into cartilage. That is how your bones grow. they actually develop into a cartilagynous model in order to get longer. So that process is just
called endocchondrial oification. But you wouldn't have known that had you not known the prefixes, suffixes, otherwise known as those roots, right? So if I were you, I would highly recommend getting like a medical Terminology book just to learn the main roots of men terms, okay? because it's going to give you those inferences about what words mean and therefore what it means in terms of structure and function. So always remember that words matter. Okay, few more real quick. Number eight is going to be no receptor. No change. No receptor. No change. Let me tell you a
quick story. Uh at one point in my life, my wife and I were working and I was actually getting Prepped for classes. She was cooking dinner. She's an amazing wife. And what was happening was I had my earbuds in. I was listening to some hardcore Mozart music, uh, classical music to study and work. Wonderful thing. But the problem was I had my headphones in and my wife, all of 5t and 1 in tall, uh, couldn't get something on the top cabinet. So, she was calling for my help. She's calling, "Hey, hey, uh, Mr. J, can
you come help me?" She doesn't call me Mr. J, but anyway, she's basically calling me, right? And I'm like, what am I doing? I'm working, listening to Boach, you know, just jamming. I had no receptor. My ears were kind of filled, right? So, I couldn't hear her and I therefore couldn't change my actions. So, I want you to know in A&P, if you don't have a receptor, a receptor is kind of blocked or plugged or not available, body's not going to change. As an example, let's take a great Clinical application to this of diabetes. So,
what is diabetes? Diabetes is when if you look inside of your blood, we have a lot a lot of lot of glucose, which is basically sugar. So let's say we have a lot of glucose inside of the blood. Well, the way the body kind of fixes that is it will release a hormone called insulin. Okay? It'll release a hormone called insulin in response to the high blood sugar. Now, insulin is something called a Hormone. It's basically a chemical signal, a chemical messenger travels in the blood and can talk to who. Who can insulin talk to
if it's in the blood? Hypothetically, any cell of the body, right? Because it's going in the blood. It's going to basically every cell. Yes. So, how does that triangle of insulin act? Well, we have cells like your liver cells, your fat cells, and what these cells will have is a receptor for that insulin, usually a protein on the Outside of the cell membrane, and it will receive that signal, that insulin, bind to it, and in response to it, we'll draw this glucose into the cell. We'll talk about that process a little later, but I wanted
you to see that there's a receptor on the cell receives the message insulin and tells that blood sugar, hey, instead of being in the blood, go to a different location, location, location, go inside the cells. And therefore, what happens to your Blood sugar? It drops, right? It goes back to normal homeostatic set point. Yes. So, homeostasis, uh, location, location, location, blood sugar life. You're seeing how these things are coming into play in a very basic example. But here's the problem. What if you say you have type 2 diabetes where we're considered insulin resistant? Insulin resistant
basically means these receptors are potentially either misshapen or they just don't respond to Insulin as well for some reason or another. So I'm going to draw the receptor shape like this. Now the receptor shape is a different what structure. We lost a structure. What will happen to the function? We'll lose the function as well. Right? So insulin now cannot bind to the receptor. If insulin can't bind to the receptor, what happens? Well, this cell can't draw in the glucose. That cell can't draw in the glucose, where will the glucose remain? In the blood. And type
2 diabetics because of their lack of a working receptor will have high blood sugar. Does that make sense? So no receptor, no change. This is very common in endocrine disorders, basically dealing with hormones and their interactions. Uh, but it's also just common in like say when you're moving your muscles. If you don't move your muscles enough, there are less receptors to receive the information about contracting the muscles. So, You're not as active, right? Your muscles don't work as well. So, there's a lot of examples of that. Really remember, no receptor, no change. Awesome. Couple more.
Number nine. This is going to be probably the one I reference the most in my class is high to low. And we've seen this a couple times already. Things in nature like to flow from high concentration area where there's a lot of it to areas of low concentration, less of it. This is Basically called diffusion. If you've ever been um say in a middle school locker room for guys, anytime you heard that ch sound, that axe body spray was eventually going to meet your nose and it was going to smell like really bad. I thought
axe smelled bad. But anyway, what happened was that axe can had a lot a lot a lot of axe chemicals inside and they were very highly concentrated. And as soon as you opened that hole to the axe through the nozzle, where did it Want to go? High to low, which is where? Everywhere else in the room, right? And in your body, molecules like to flow from their high concentration to their low concentration. as an example here with glucose. Typically, glucose is going to be a little lower inside cells. So, there's this innate uh desire for
glucose to flow from high concentration in one location to low concentration in another. Now, the kicker here is sometimes we're going to have some Barriers like these cell membranes that will prevent things from moving. So, that's why uh we need some different channel proteins and other types of things we'll talk about a little later. But, I want you to just know in nature things flow from high to low. Another great example is your lungs, right? There's a lot of oxygen out in the air and comparatively little in your blood. And so therefore, when you breathe
into your lungs and it gets to these little Air sacks called alvoli. So let's imagine these are alvoli. We got some really thin flat cells in the base of them and you're bringing in oxygen from the outside environment. Therefore, you have a lot of oxygen inside your lungs at any given point in time. But at the bloodstream at this point, you've actually used up a lot of the oxygen. It's in the pulmonary system. Talk about that in AMP2. We're going to have relatively low amounts of oxygen in the Blood at this location. So, where will
the oxygen want to go? Simply high concentration to low concentration into the blood. Whole respiratory system, basically your breathing system, can be explained by high to low. Awesome. Last one. Number 10. This is my new one. I've actually added a new one and it's kind of funny. Uh, that damn beaver. [laughter] That damn beaver. This is a play on words. I did not swear. It's fine. Now, This one takes some explaining. Uh, what does a beaver do? Well, a beaver sees a wonderful river, right? So, here's like a river. It's going to flow this way.
Okay, to the left for this reason. Okay, we're reading right to left like Hebrew, right? So, the river is flowing down this way. And as it flows, there will be different products, things like fish, right? Uh, we'll just say here's a fish. I can't draw a fish. Yeah, that works. There we go. There's a fish. That's an Eight. It's fine. There's fish flowing down the river. Maybe some nutrients, maybe some plant matter, etc. Right. And as it flows downstream, it's going to continue getting there. But if a beaver comes in, this is going to be
my beaver. Okay. Uh, little smile on it. Do they have ears? I don't know that. No. No, that's going to be a squirrel. But I know they have that little weird little tail thing, right? Yeah. There we go. Okay. So, here's here's our beaver. That Is the [laughter] Please make fun of me for that beaver. Uh, what a beaver does is it'll break down twigs and it'll put them in the middle of that river, right? And build that dam, right? So, that's where the dam comes from. This is a dam that the bu the beaver
is building. Now, what will happen? Well, there's several things that will happen. Well, we know that there's probably some even bigger fish down here, right? Why am I keep Drawing eights? There's some bigger fish down here that need to eat some of these things, right? So they want these products to flow downstream, but they're no longer going to get it, right? So the things downstream are going to disappear. But what will happen to all these things? Well, they will keep building up and building up and building up right in front of this dam. So basically,
this is like an assembly line. As the assembly line's coming down River, if there is a break in the system, everything downstream is basically going to disappear. Whereas everything upstream is going to build up. This is really important in what's called metabolism. I'm going to write that up here. What is metabolism? Fancy word for just saying, hey, all the chemical reactions of your body. That's what metabolism is. Your body is doing about 360 times a trillion I I think it's 360 trillion times a trillion Chemical reactions like every second. It's something outrageously high. But a
lot of these things are in a chain. So A maybe converts to something like B which converts to something like C which converts to something like D. So there's this like assembly line like we'll see in the citric acid cycle or glycolysis or the electron transport chain that go in these sequences. And usually these sequences are catalyzed. So basically ignited. These chemical reactions are Ignited by little proteins called enzymes. Very important. And if the enzyme is working properly, it will do this reaction. It'll help A turn into B and it'll help B turn into C,
a specific enzyme from B to C and C to D and etc. But what if we lacked an enzyme? What if we lacked say the enzyme that converts B to C? So now we no longer have this bridge. So this bridge is now broken. Well, will C and D even exist now downstream? No, that will disappear. Well, what will happen to A and B? Well, A will probably convert to B a lot and B will get really, really, really big. And a lot of the times when something builds up in the body, the body's like,
"What the heck? We have a lot of this. We need to convert it to something else." We will see that in specifically glycolysis. When we build up way too much pyuvate, we're actually going to make some lactic acid instead because we broke the chain specifically because we Didn't have oxygen. But that's going to be a later story. So, if you memorize these 10 core concepts, you'll see them popping up over and over and over again because what these things are are schemas. They're big picture ideas. Think of them as like a big picture box that
you can fit a lot of different things in. So, for example, you have a box that says high to low. What you can now do is talk, hey, well, the respiratory system, right, where we're Bringing in oxygen, getting out CO2 of the body, that is just high to low, right? Bringing glucose from your blood into your cells, that's just high to low. So, you're adding these new bits of information into the schema so you can understand it better. Have you ever been in a class where the teachers just taught you these random things and you
had no idea where to put them? They're all like just so scattered. Well, what we're doing here is different. We're Giving you the boxes ahead of time and then we're going to put the information in, whereas your other instructors just try to give you a bunch of information without the boxes. It's not their fault. It's just a good way of learning, right? So, that's what we're going to do here in this class. So, we got through the core concepts and what AMP is. Now, we've got to move to levels levels of organization if I can
still talk and talk about kind of small picture to big Picture in A&P. and then we'll talk about homeostasis a bit more which is a core concept. So as a quick little break I want to let you guys know that on organizedbiology.com there's a lot of great resources that may be helpful to you in your&p nursing journey. So feel free to click the link in the pin comment in [music] the description or just type in organizedbiology.com and you can check them out. Thanks. All Right, so levels of organization. This can trip up some students. So,
we're going to first use an analogy to help you understand how it connects to something that you do know about. So, let's just take any business for example like Amazon or Apple. And what you'll have with these things is think of the big picture overview. What is the business? Well, in this case, we're going to say the business is Apple. Okay? So, Apple is going to be our Business. I wish I got commission just for mentioning them, but I don't. Uh, somebody fix that. So, this is the business big picture idea. Everybody knows what Apple
is, right? But if you break apart Apple into the next level of organization, like how is it organized right underneath the business? Well, typically you're going to have a lot of different departments, right? So, Apple will likely have departments for say it, uh, a department for say maintaining Products, a department for marketing, a lot of different departments, right? So this is basically big groups or think of just them as separate buildings that are going to be operating as a separate function but the whole goal is to support the business right and then from there the
departments usually have individual offices within them right so maybe you have a boss and they've got a team of maybe 10 to 15 people all working towards a common function right So there's similar workers I'm going to say similar workers common function, right? Common function. Whereas, when we're talking about the departments, they're going to have a lot of different offices underneath them coming together for a common function as well, right? Like marketing. Okay? So, let's just write that as an example like the marketing department. Okay? But there's other departments. But then from there, not Only
do we have offices, BUT WHO ACTUALLY DOES THE WORK? WELL, it's the people, right? It's the people within the offices, right? So these are the workers that are actually doing the work to support the offic's function, to support the department's function, to support the business's function. So Apple is basically run by a bunch of different organizational levels. Yes. But ultimately, who's doing the work? Like if anything failed and it would Basically screw the business over, who would it be? It'd be the people. If the people didn't do the work, nothing would happen. Yes. Use this
as an example in A&P. How? Well, what does everybody know? Well, everybody knows that there's a thing called a human body, [laughter] right? Everybody knows Apple, right? This is the biggest level of organization that's going to be considered the organism, right? It's the living, breathing human being. Everybody Knows. But how is the next level supporting the human? Well, we know that there are 11 organ systems of the body, right? things like the cardiovascular system or the respiratory system or the urinary system. These are like departments where they've got basically their separate function, but there's a
lot of different people working to fix that up, right? So, what are the organ systems made up of that? But you probably guess, well, an organ System is two or more organs for a common purpose, right? So therefore the next level of organization down would be simply organs. Things like the heart, things like the lungs, the trachea, the blood vessels. These are all organs and multiple organs fit together with the system to support the human, right? To keep homeostasis. But then what are organs made of? This is a tougher one. Well, organs are two Or
more tissues that are coming together for a common function. Now, this is a new one. A lot of the people who come into&p, they they've heard of organs, organ systems, and the human, but they haven't heard of tissues. What are tissues? Well, let's get into that. That's the next level of organization. So, tissues, this is where things kind of break apart with my analogy. Tissues are kind of like the offices, right? And the department is Kind of a blend of these two. So, offices, remember, we have similar workers with a common function. Well, tissues are
going to be two or more cells with a common function. Now, I'm going to stop here for a second because I want to explain some of the levels below here. So, tissues are clusters of cells with a common function. The four main tissue types we'll learn about are going to be epithelial tissue, basically the Lining of the body. So, anything that's lining a a cavity. So, basically your skin is going to be an epithelial tissue. That epidermis of your skin, you're going to have the lining of the intestines, that internal lining is going to be
epithelial tissue. Then we've got muscular tissue. Anything that contracts to move something. Then we've got connective tissue. Anything that wraps, binds, or transport something. And then we've got nervous tissue, Basically the signaling tissue of the body. So these are the four kind of offices you could think of of the human body. And if we have two or more of these, once again, it's going to be an organ. So, as an example real quick, the heart, if I'm just going to draw the heart here, that's again an organ. Now, the heart has a lining to it
on the outside and the inside. That's going to be epithelial tissue. But then you're also going to have a very thick red Middle section, and that's going to be the muscular tissue that actually contracts to pump blood out of it. But then from there, you're not only going to have that, but you're going to have other tissues around the heart and inside the heart that will kind of keep the heart together. Like in the septum, there's going to be some muscular tissue, some connective tissue that's going to hold it together. So, we got connective tissue.
And then, not only That, we also have some nervous tissue that will signal when the heart should contract. So, you see how multiple tissues, all four in this case, come together to form an organ, the heart, to do a common purpose, pump blood, right, to the whole body. So that is kind of how tissues and organs are organized. We're going to go through the details of these a little later on in this class, but let's keep moving on. What are tissues made of? Well, they're clusters Of cells, right, with a common function. And I real
quick before I forget this, the prefix for tissues is always going to be histoylogy. Histo refers to tissue. And yeah, we'll just stick with that for now. Now, tissues. What are the tissues made of? Tissues are made of cells. And I want you to really star and circle this because cells are the stars of the show. At this point, I want to remind you that workers are the ones that make the Business run in your body. Cells are the ones that make your body run. You got 30 trillion of them. They are doing everything for
you right now. If you're speaking, it's because the muscles in your diaphragm and a variety of places are contracting to help push sound out. It's going out my nasal cavity which is lined with epithelial tissue etc. There's a lot of cells doing the work for you. So couple things on cells. This is the living Level of organization. If something is alive, it's because it's made of cells. So the living unit of your body are the cells. And so anytime we're talking about some issue with the body like say oh the heart is failing or there's
edema in the body usually it's because a cell has screwed up. So in terms of structure function cells are the main one. Now cell is always going to have a prefix cyto like cytology and you'll also see it ending in site a lot of the times Because words matter. So as an example a myioite when you look at the word me myioite myio if I can spell myioite that translates to muscle cell or maybe you heard of keratinocy keratin is a sk basically protein in your skin cells a keratinocy is a skin cell protein in
the epidermis so again any time it ends in sight it's going to usually be a cell that we're talking about so with cells real quick I want you to remember that a Cell has a main outer membrane and we're going to learn about that a little later and that's mainly going to be made of lipids. It's a phospholipid billayer but it's made of a lipid. That's kind of a defining structure that separates the intracellular environment from the extracellular environment which typically is made of a lot of water and we know that lipids don't mix well
with water. So, we kind of have this separation of the two locations. Okay. The second thing I want you to know about a cell is that it's got a nucleus. Okay. The nucleus is going to have a lot of the DNA in the nucleus nucleus. And that DNA is basically a recipe book for how to build the cell, specifically how to build the cell's protein. So when we read that DNA, we'll transcribe it onto mRNA and it's going to be built into proteins. Now, these proteins come in a variety of different shapes and sizes, and
they may be in different Places. So I'm drawing the proteins in pink here. P for protein. So, I'll just write proteins here. And the proteins, I want you to remember, are a level of organization down from cells. And proteins are also the structure and function of your cells. So, remember when I said like if you're doing something, it's because your cells are doing it, right? Well, the cells are able to do it usually because the proteins are doing it for You. As a great example, your muscles are contracting because your muscle cells are contracting, right?
But the muscle cells are contracting because the actin and meosin proteins are interacting in such a way to pull the cell tighter to contract it. So really if you're doing something it's because the cells are but if the cells are doing something it's usually because the proteins are doing it for them. And proteins typically end in that n. You'll See a lot of that. So I mentioned actin and meosin. They always end in that in so you can know it's a protein. Earlier we talked about insulin. That was also a protein. Fun fact. Okay, so
that's just a brief overview of the cell, the nucleus, the membrane, the proteins that it's producing. But it'll also usually have mitochondria, the powerhouse of the cell, the only thing you remember from biology class. And that is a very Important organel that will produce that helpful, helpful, helpful molecule of ATP. ATP, cellular currency of energy. We'll talk more about that in chemistry. So when you think of the cell, the cell needs to know how it builds itself. How does it know that? DNA reads it to make proteins to help the cell do the stuff it
needs to do. It's also got the membrane to separate extra and intracellular environments and it's also Got some organels to help with ATP production and a lot of other organels to help with uh keeping the membrane steady uh helping the cell divide when it needs to regenerate or fix something. Um a variety of different organels we'll talk about later on in the cell biology unit, but those are some main ones. Now you'll notice then can we just stop at this level of organization? Can we just say like, oh, we got cells and cells do these
things. No, because you're Realizing the cells are made of other multiple components, right? Cells, if you divide them up, have organels. Those are tiny organs inside the cell like the mitochondria, like the nucleus, like the endopplasmic reticulum that are tiny organs helping the cell do its function. And not only that, but the organels also have lipids and like carbohydrates and proteins associated with them to build the organel itself. Those are all macromolecules. All macroolelecules translating to big molecule that builds the organels that build the cells. You've probably heard of these before. Big molecules. They're in
your diet. They are your proteins that you eat. They're the lipids that you eat. They are the carbohydrates that you eat. And rearrange them in such a way to build yourself or to use as energy. And you'll also have nucleic acids like the DNA itself to help build your DNA, your your genetic code. So We'll go into the details of these as well in chemistry because these are types of chemicals, molecules, right? And macroolelecules are big molecules, but we also talked about like oxygen earlier, right? Oxygen is just a normal small molecule like oxygen, O2,
basically two or more atoms put together to form a molecule. But then we finally have what? Atoms. Atoms make up everything. So you can't trust them. Just kidding. Uh but atoms Are the base unit of all matter. These are things like carbon, things like hydrogen, things like nitrogen, right? And then oxygen is also, this is a weird one, oxygen is also an atom. And then we also have a phosphorus is a common one in your body. Okay? So if we put say two oxygen atoms together, what do we form? Well, we form O2. That's a
molecule. Yes. What if we put hydrogen, two hydrogen's and oxygen together? Well, we form water. That's a molecule. But then What if we put a ton of them together and make something called C6 H1206? That's glucose. That's a macroolelecule. Bigger molecule because it's got six carbons, 12 hydrogens's, six oxygens. So do you want the good news or the bad news? Well, I'm going to tell you the bad news first. In order to understand how the body works, what do you need to know? You need to know how atoms work and how molecules work and how
macroolelecules Or are organized in organels and cells and tissues and organs and organ systems. You need to know all of this in order to understand how the body works. And in order to take care of your patients in the future, you need to understand these things because depending on say what drug you give them or what type of intervention they need, you might be affecting them on a different level of organization. So you need to know what are we acting upon, Right? But the good news is you have the map. You have basically the organizational
structure in your mind to know where we're talking about. So when your instructor says, "Hey, we're talking about phospholipids today." You're going to be like, "Oh, lipids, right? What level?" "Oh, or macroolelecule." So that's probably going to build an organel. I'm probably going to build a cell, right? Or if they say, "Hey, we're going to study Hisystologology today." You're going to be like, "Oh, well that's just talking about clusters of cells with a common function, tissues, right? So hopefully this is a good map for you to then use when you're studying so that when you
see these diagrams, you know what level you're on. So you therefore know what level we're talking about. Awesome. So levels of organization. Huge topic. You really, really, really need to get in your mind. Now, the last thing we're Going to talk about today, most important probably, is homeostasis. How do we keep our body in that set range to help optimize our life, essentially our survival? So let's check it out next. So, you've probably noticed throughout this lecture, I'm not really big on definitions because I remember in middle school and high school, you just have to
memorize a definition, you get points for it. Uh, but I like to air away from that because if you understand the Concept, typically you can define it pretty well. But in this case, I do want to define that term of homeostasis because it's going to come into play a couple different times. So again, with homeostasis, I like to break the word down, but it's not very helpful. Basically, homeostasis means similar standing. Similar standing. What that translates to is again this idea that we need to set a set point of a variety of different variables like
Blood pressure, body temperature, etc. and keep them in this fixed range in order to optimally operate. But with homeostasis, we know that it is the ability. Okay? So not only like we have these set ranges but we have the ability of our body our shoot of our bodies to what maintain big word there a stable set or a set range of internal conditions. Okay let's break that down a little bit. Okay, it's the ability of our bodies to maintain a stable set range of internal conditions. One ability, if our body has the ability to maintain
homeostasis, we are functioning well. But if we lose this ability, if we are not capable of doing this, we typically call it a disease. A disease is basically just the inability of your body to maintain homeostasis in some sense of the word. Okay? So I want you to remember that Absence of homeostasis typically translates to a disease. Great example, let's say uh you're sick with malaria or something, you spike a fever, your blood oxygen drops, you have a disease because these homeostatic variables are out of range, right? And therefore you could die. The disease is
malaria. It's caused by a parasite in that case. Okay? Uh same thing with type two diabetes, type 1 diabetes, these are diseases where you can't regulate your blood sugar levels. So anytime you're in unable to maintain homeostasis in some sense, you have a disease. Awesome. Now of our bodies to maintain a stable set. Here's the thing with homeostasis. Let's say you have a body temperature of 98 degrees and that's true north. That's like homeostatic set point. Will you stay at 98 degrees all day every day for the rest of your life? No, I mean a
lot of the times you start exercising, so maybe maybe your body temperature goes up Pretty high, but then you're able to cool yourself off, right? Maybe you go outside and you're a little cold for a little time, but then you shiver and you get back to warm normal, right? So, you can kind of fluctuate in homeostasis, get a little too warm, a little too cold. But the key word is be able to maintain it. Like, are we capable of bringing it back down if and when we need to? But it's possible to get out of
homeostasis here and there. In fact, It's a good thing. When you start exercising, your blood pressure probably skyroats about 190 over 100 or like 180 over 90, something like that. That's elevated blood pressure, but is that bad? No. You're just meeting the demands of your body. So, you're basically saying, "Hey, we need a higher blood pressure to feed ourselves better so that we can optimally exercise." So, we can get out of homeostasis here and there. It's totally fine, but we need to Be able to bring it back down. If we're not able to bring it
back down or up, I guess, to that set point, we have a disease. Good. Okay. So then stable set range. Typically we're going to have a range for a variety of different homeostatic variables. I mentioned body temperature, right? The range of 99 degrees Fahrenheit to 97. If you're between this, you're normal. You're you're in homeostasis. You're fine, right? There's typically a middle, but You're pretty pretty good in that range, right? Same thing with say blood pH or blood acidity. It's going to be 7.35 to 7.45. Typically blood glucose levels you need about 60 to 100ish
depending on the person. Uh I think it's milligrams per deciliter. I haven't looked that up in a while. Um but you see that it's a range, right? Uh you'll learn a lot more about electrolytes later on. Like the range of potassium is 3.5 to 5. Sodium's 135 to 145. There's a range. So if you're in between it, you're typically normal, right? So just keep that in mind. And then it's all internal conditions. Have you noticed a lot that I'm saying blood pH, blood glucose, body temperature, which really is your blood temperature? Essentially, a lot of
these things deal with your blood. What did I say about your blood? Where was your blood in your body? Your blood is technically inside your body. That is considered the Internal part of your body is your blood because it goes everywhere. So, if you keep your blood good, typically you're keeping your body good. Okay? So, that's the breakdown of the definition. That's why I like to break it down for you guys. Now, let's say though we get off of homeostasis. We need to be able to respond and adapt to it. So, let's see how we
do that. So, what we're going to draw is kind of a feedback loop. And this is going to be a negative feedback Loop. Negative feedback loop. That is going to basically be whenever our body gets out of homeostasis, how do we bring it back to normal? Now, anybody can understand this if you have hands. Okay. So what I want you to do is take your hands and say this is the set point. This is 98 degrees. This is 7.4 pH, right? This is the actual condition of your body. The other hand, what if it got
too high? What if your body temperature went too High? Uhoh. What do we need to do? We need to have the capacity to bring it back down towards the set point, right? What if it got too cold? Well, you need to have the ability to bring it back up to the set point. Yes. Negative feedback loops are just the ability of how we do that. So if we get too high, a negative feedback loop will result in bringing it back down. If we go too low, the negative feedback loop will result in getting back up.
That's all it works. Okay? But there's several steps in that. So what I want to show you is kind of the steps of that. So let's say as an example, your body is at 98 degrees Fahrenheit. Okay. What we're gonna say is that this is called I'll draw it in pink, the set point. Okay? So, you always have a set point, but then inevitably you have some sort of stimulus that's going to occur. So, let's say uh you go outside on a really hot summer day and now your body is at 101 degrees Fahrenheit. Uh-oh,
your body temperature raised. Are you in homeostasis? No. You're out of it. Right? So, this is going to be called the stimulus. something that happens that gets your body potentially out of homeostasis. Well, we just had a stimulus. What has to come next, my wonderful AMP students? Anytime you have a stimulus, what do you have to have? When my wife was calling my name, she was the stimulus. What was I lacking? The receptor. So, anytime there's a stimulus, I want you to burn into your brain. A stimulus has to have a receptor. Got it? So
the next thing that will happen is that the skin detects high temperature. Okay? Typically you've got these thermo receptors in your skin. You also have them in your hypothalamus in your brain, but they're going to detect that temperature because the skin has Receptors for it. Okay? So you have receptors for the temperature. Now what? Well, you would think that the skin would just immediately start sweating, right? But the skin is smart and it's got these nervous tissue, these basically sensors, receptors that need to communicate to somebody about it to make sure we know what response
we need. So, what happens is once the skin detects the high body temperature, what it will do, it'll it'll send Specifically action potentials, but we're just going to call them signals. It'll send signals to the brain, specifically a region called the hypothalamus. That's like the homeostatic regulation center of the body. It starts with an H, hypothalamus. It's right below the phalamus in your brain. It's going to be the main regulator of homeostasis. I want you to memorize that. Homeostasis, hypothalamus. So, send signals to the brain, the hypothalamus about that temperature. So what the brain, the
hypothalamus is acting at as is something called a control center. Okay, the control center. Think of that as basically central command. He's going to be the one or she's going to be the one uh to decide what happens next. So all of the information needs to get to them first and that's going to be the brain most of the time, but a lot of the times it's Going to be an endocrine gland or some other structure. So from there, the control center, hey, we notice, whoa, the stimulus is high because we were talked to by
the skin's receptor sent signals back to the brain. Now the brain is like, oh shoot, we need to cool the body down. So is the brain by itself capable of cooling your body down a little bit? Like we can talk to blood vessels, dilate them, and help the the heat get off, but again, those are blood Vessels. It's not the brain itself. The brain has to talk to somebody else to help us with this. Who do we need to talk to? Who do we need to talk to in order to cool our body off? Well,
we need to talk to specifically the sweat glands, don't we? Sweat glands because the sweat glands if they are if they sweat it'll cool our body off. Well, what we call the sweat glands here are the aectors. These are b this is basically the tissue the cluster of Cells glands or cluster of cells that can make sweat that will actually be able to help fix the issue at hand. That's the aector. So what the aectors will obviously start doing is sweating. They will release sweat, right? That sweating is just considered the response. So the sweating
is just the response. And from there what will happen? Well, the body returns to the set point. That's a negative feedback loop. Are we Done? No, we're not done. Think about it. Did we fix the issue by sweating? Yeah, because we just returned it back to the set point. But what's the problem? What if this kept going? What if this kept going and going and going? We would just keep sweating and sweating and sweating and sweating. We don't want that. So what happens is when we respond and we get back to the set point like
the second Time around. So like we've already done this, we've cooled our bodies off. What do we need to do? Well, we need to tell the receptors who are able to detect the temperature that we're at normal body temperature now, right? We're at normal body temperature, right? So what will the receptors do? Well, they will stop detecting it. they'll stop sending the signal which will stop this which will stop this that damn beaver right Whenever we stop something upstream everything downstream stops so therefore we stop sweating so you see how once again core concepts come
into play a lot no receptor no change you need that receptor if you didn't have the receptor you wouldn't be able to detect it once we fix it we got to cut that signal off make the dam so that we don't have anything downstream happening so that is a classic negative negative feedback loop and you could also imprint it or Impose it onto say what if the body went too low. Well, the body temperature is now too low. Who would detect it? The skin. The skin would tell the brain. The brain would not tell the
sweat glands. They would tell the skeletal muscles. Interestingly, it would start shivering, right? Because when you shiver, you produce heat. And when you produce heat, so the aectors would be the muscles. The response would be shivering. Body would come back up to homeostasis once again. And the response brings it back down or the response brings it back up towards that set point. That's a negative feedback loop. Classic examples. Now, that being said, that was a negative feedback loop. We have special instances where we there will be positive feedback loops and I want you to do
it uh with your hands real quick with a positive feedback loop because it'll help you understand how it works. So, here's your set point of some sort. Here's your Actual condition. What a positive feedback loop does is when we get here, the response will further push it away from homeostasis and further push it away and further push it away and further push it away until something crazy happens or something good happens and then it'll immediately come back down. So, a positive feedback loop amplifies the initial stimulus. So, a positive feedback loop amplifies The initial stimulus.
amplifies initial stimulus. They are less common. Usually negative feedback loops are used like 99% of the time, but positive feedback loops are used occasionally. Okay. So again, compare and contrast. Positive feedback amplifies it, makes you go out of it further. Negative feedback loop resists it or brings it back down. So it opposes the initial stimulus. Right? Now, couple examples of this. I'll just give you I'll give you a couple. Uh Pregnancy and child birth. So child birth as well as blood clotting and then so these are both in a way good things right [laughter] uh
pushing baby out child birth is positive feedback loop blood clotting great thing that you need to do anytime your blood vessels are burst great positive feedback loop but it can also be uh bad okay so as an example atherosclerosis the hardening of your arteries Due to plaque buildups inside of them that's also a positive feedback loop so Actually, sometimes positive feedback loops are a disease state that are not a good thing, but sometimes they are a good thing um for the body. Okay, so let's just take one example. This one's a fun one to teach.
Child birth. Okay, so this is going to be a terrible diagram. I apologize in advance, but this is the last thing we're teaching. And then lecture two coming up, we're Going to talk about chemistry. Vitally important for you guys to know. So, what I'm going to have here is going to have a baby. Okay, so here's a baby. He's going to do a nose dive. Okay, where's he going to do a nose dive out of? Well, he's got to come out of mother's body. So, here's going to be mother. I apologize to mothers everywhere. Okay.
So, here's mother. Uh, this is what she's going to look like because I can't draw anything. Well, there's mother. Cool. Woohoo. There she is. Okay. So, baby's ready to come out, right? So, here's baby ready to come out. Well, problem is we got a cervix here. Cervix, basically a pretty thick tissue that is basically a circle. Think of it as almost like a sphincter that is open and close. It can open and close. Well, during the duration of the pregnancy, what do you want the cervix to do? This. You want it to be closed. You
want it to be closed so the baby stays inside and Develops properly. But when baby is ready to be born, what begins happening? Well, the big noggin of the baby begins pushing on the cervix. If you start pushing on a cervix that can open, what does it start doing? It starts stretching. So, the stimulus right here that happens first is the cervix stretches. Now I want you to think about that. Stretch your skin out like pull it. It's able to be pulled, right? What sensation Do you start feeling? A not good one. You start feeling
pain, right? It's not comfortable. So is the stretching of a tissue a good thing? Usually no. But this is a positive feedback loop because when the cervix stretches and opens up slightly, do we want it to be a negative feedback loop and just close right back up? fix the stretch. No, we want to get the baby out. So, we want the response of the cervix stretching to eventually be stretch more and stretch More and stretch more and stretch more and stretch more until hopefully baby's born. Does that make sense? So, we're going to amplify this
initial stimulus. This is the stimulus that started it, right? I draw that in pink. So, this is that stimulus. Okay. So, the cervix stretches. Ah, crazy. Well, who do we need to tell about that? Well, probably the brain because the brain is like kind of controlling everything in your body. So the cervix stretches and that sends a Signal to who you think? Hypothalamus again. Okay. So we signal to the hypothalamus who has the um basically the receptor to receive that information. Now I just broke my own rule. You should like make fun of me in
the comments. The cervix stretching, that's the stimulus. What do we need to have first? We have to have receptors. So inside the cervix itself, we also have stretch receptors, which is why I skipped it. Stretch receptors. And those stretch receptors will basically be the receptors that send the signal to the hypothalamus. My apologies. Well, in response, the hypothalamus is like, "Hey, a baby's coming. This is great. We better put this baby out." So, the hypothalamus via the pituitary gland, the posterior pituitary gland, will release a hormone called oxytocin. Oxytocin is like a little hormone travels
in the bloodstream, goes Everywhere, and that oxytocin will come in. Well, this is by the way the response essentially. So this is kind of theector or kind of the response signal whatever hypothalamus is still the control center. This is a little weirder example and this is the response of the control centers to send a signal of oxytocin through the blood. Now oxytocin will travel specifically to the organ of the uterus. Here's the uterus holding the baby. Very muscular Tissue. And that oxytocin is like a signal, right? What do we have to have? we have to
have a receptor. So the uterus will receive the receptor o uh the stimulus of oxytocin and in response to it the uterus will contract. Woohoo. When we contract the uterus contract the uterus baby will start pushing out further. If baby starts pushing out further what do you think happens? cervix stretches again, which will Trigger the stretch receptors, which will trigger the hypothalamus to release more oxytocin, which will trigger more contraction, which will you see the positive feedback loop. We're stretching, stretching, stretching, stretching. Eventually, baby will come out. Woohoo. And be crying very sadly. Um, but
a good thing actually. Baby's crying. It's a good thing. They're alive. They're breathing. Um, so baby's Born. What does the cervix do? Well, it's stretched like crazy. But as soon as baby's born, cervix starts to relax back and it'll stop that feedback loop. Now, what's interesting, this is a positive feedback loop, right? The goal of oxytocin was to contract that uterus to get baby out. But oxytocin, you've probably thought of that as like the love hormone, right? It's actually the binding hormone. That hormone influences Mother's imprinting onto baby. So oxytocin kind of has a dual
purpose here, right? To contract the uterus to get baby out, but also to help that mother and baby bond. And actually, if a father is present in there too, he actually releases some oxytocin too in response to all this. So it helps just basically the whole family bond, an amazing amazing function of the human body. Now before we sign off for the day, I recognize that I'm not going to Cover every single topic that an instructor could in [music] all these lectures. So, at the end of each video, I'm going to have a few other
videos to the side, as you see right now, of like organ systems overview as well as directional terminology that I'm going to cover more in the lab [music] section rather than the lecture. So, hopefully they are of benefit to you.
