Hello. In this video we're going to learn about the major requirements for human life. Then we're going to learn what homeostasis is, why it's important, and how it's regulated. So let's start with this image here. We see a variety of foods, our nutrients.
We have a note that food is converted into energy in metabolism. And then we have an extremely simplified diagram of the metabolic processes that occur in a cell, okay, where glucose, so sugar, goes in and building blocks come out as well as energy. So let's talk about the role of oxygen in this process.
just generally oxygen is needed in order for cells to extract energy from food. So in this process of cellular metabolism that we'll learn a bit more about later, oxygen is needed at the end of a long multi-step process in order to get significant amounts of energy from the food that our body takes in. and then breaks down. So the reason you have a respiratory system and a cardiovascular system to get oxygen into your body and then disperse it to all the cells of your body is because those cells need oxygen at the end of an important metabolic process happening in the cell.
Okay, so let's go on to the other. to the nutrients part. So I'm going to actually break down nutrients a little bit more into macronutrients and micronutrients. Macronutrients just means nutrients that your body needs in large amounts like water and protein. Okay, we're going to talk about water first.
Water is the most abundant chemical in your body. It is the basis of intracellular fluids, meaning the fluid inside of cells, as well as all extracellular fluids, which is the fluid outside of cells. So extracellular fluids would include things like the interstitial fluid or tissue fluid that bathes the tissues of your body, as well as the blood plasma. Okay?
So because water is the basis of all of these fluids, it is called the solvent of life. And because it's the basis of said fluids, basically water, the chemistry of water is going to determine the chemistry of life. So water is really important and we will learn more about the chemistry of water. in subsequent units. Just one note that I have here about water which relates to the type of bonding that it undergoes is that it takes a lot of energy to change the temperature of water, okay, to raise it or lower it.
So this is actually very important for life because it helps us to maintain a stable body temperature. So more about water later. Let's go on and talk about the other macronutrients.
The other macronutrients are carbohydrates, lipids, and proteins. And they are used mainly for energy, or I should say they're known as the energy-yielding macronutrients. Now within the body, so we take in These macronutrients in our foods, they're broken down in the digestive tract and absorbed.
Within our body, our cells use them as an energy source, as well as using them as building blocks to build the complex molecules that our body needs. So larger molecules come into the body, they're broken down into They're small little component parts and then those component parts can be used to build back up the structures of our bodies. In addition to the macronutrients, we have micronutrients, which are essential but only in very small amounts, hence the name micro. The micronutrients are basically our vitamins and minerals.
They have a lot of very important roles in the body. for example, maintaining body fluid balance. They are needed for electrical conduction in the nervous system. And they're also needed for enzymes to function.
So enzymes are a type of protein that we'll learn more about in subsequent chapters, but we'll see that enzymes have many, many important roles. And many of them use... vitamins or minerals as cofactors to help them function.
Okay, let's go on to talk about temperature and heat. Heat is actually given off as a byproduct of many metabolic reactions, which is a good thing because we know that a particular temperature range is needed to maintain life. This is because enzymes and metabolic reactions require an optimal temperature in order for them to occur at the correct rate. If it's too hot or too cold, enzymes don't function properly, and this can cause damage to the body if it occurs for long periods of time. The last factor we're going to talk about here is pressure.
Okay, so pressure is the amount of force inserted by one substance onto another. And it might not be something that you have thought much about in terms of an essential requirement for life. But hopefully, by the time this class is through, you will.
So. Pressure is required for many essential body processes. This image is just showing you a simplified diagram of the lungs and different pressures. So proper pressure is essential for breathing.
It's also needed for filtration in the kidneys and blood flow through the blood vessels, which we know of as blood pressure. we'll learn more about the various pressures as we move through the course. So let's go on and talk about homeostasis.
So what is homeostasis? Well, it is the maintenance of a stable internal environment. So all of the organ systems of the body are continuously working together to bring nutrients to cells, remove waste products from cells, and respond to changes in the surroundings.
When all the organ systems are working together as they should, we have an internal harmony or balance that is homeostasis. So there are innumerable factors. within your body, temperature, chemical levels, blood flow, they're all maintained within a specific range in order to maintain homeostasis.
These ranges are mainly set and monitored by the nervous system, although the endocrine system certainly helps. Now, of course, you know, there is variation between people. Right, so these homeostatic ranges can vary between individuals and with differences between people and things like different life stages.
So what happens if there's a loss of homeostasis in the body? Well, disease or death. So the body is always trying to maintain homeostasis.
When homeostasis gets thrown off is when we get ill. If the body cannot... cannot get that illness under control and bring things back to homeostasis, it can result in death.
So let's look at a general homeostatic mechanism that's going to apply to many different situations. So first you're going to have some sort of stimulus, some sort of change. the environment. This change is detected by sensors or receptors as they may also be known.
So there's many different types of receptors and they're specialized for detecting all sorts of different stimuli. For example, there are receptors that detect different chemicals like blood or calcium as well as things like pressure. Okay, so an activated receptor then sends a message to the control center. So the control center regulates the set point that the body is striving to maintain. So the set point is just referring to the normal value or range of values that as I said, that you are working, the body is working to maintain.
The control center is usually part of the nervous system, could be endocrine or sometimes even both, but mainly this is a structure within the nervous system. So in response to detection of a stimulus from the receptor, the detection of a stimulus by a receptor, which then notifies the control center. The control center then activates an effector, which carries out the response.
Okay, so the effectors that are activated is a muscle, skeletal, smooth, or cardiac muscle, or a gland that is stimulated to respond into such a way that the system is brought back to homeostasis. Now, there's two general feedback mechanisms that regulate homeostasis. They are negative and positive feedback. A negative feedback is by far the most common. Negative feedback, some common examples include temperature, which we'll look at in a minute, blood calcium and blood glucose.
But in general, you know, if you don't know otherwise, you should just assume that a factor is regulated by negative feedback because it pretty much always is. So what happens in negative feedback is that as a change occurs, negative feedback just moves the system back to that set point or back to what is normal. So let's talk about body temperature.
Now, if you're hot, let's think about what effector mechanisms are activated, okay? Or to put it another way, when we say effector mechanisms, we mean what are the signs and symptoms of being hot, okay? How do these responses help you to cool off, all right? Well, you know that you sweat. You're cutaneous, that means your skin, your superficial blood vessels dilate, right?
And that gives you more of a rosy color to your skin. Your breathing increases. All of these factors release heat, which helps to cool you off.
How about when you're cold? What effector mechanisms are activated? Meaning, what are the signs and symptoms of being cold? how are they helping you to warm up?
Well, your cutaneous blood vessels will now constrict, okay, in an attempt to retain the heat closer to your body core. Another thing that commonly happens is shivering, right, where you have an involuntary contraction of skeletal muscles that's helping to produce heat. So that's just one example, but we'll see many examples of negative feedback.
as we move throughout the course. Positive feedback is interesting and different. In positive feedback, you have a change in the system in which the system is actually temporarily pushed farther away from the set point rather than immediately being brought back to it.
All right, so positive feedback. situations are temporary and unstable but ultimately necessary okay so some examples of positive feedback are blood clotting and labor and during child and childbirth so blood clotting stimulates further clotting okay and this temporary situation of creating further clotting is important to stop bleeding. Now, blood clotting is, of course, complex, and there's all sorts of regulatory mechanisms to make sure clotting doesn't happen when it shouldn't, because that is in itself very dangerous. But blood clotting occurs through a positive feedback mechanism initially. And then there's the process of labor and delivery.
So... During labor, uterine contractions cause a hormone release, which stimulates ever-increasing contractions. And the process is cyclical and leads to amplification of a response, ultimately leading to childbirth. Okay. So this wraps up our coverage of the major requirements for human life and homeostasis.
In the next video, we will look at the general organization of the human body.