Hello. Welcome to Chapter 1. In this chapter we will be focusing primarily on 3 sections: sections 1.1, 1.5, and 1.6 and these are the sections of the chapter you should focus on when you are reading the textbook. As the name of the chapter suggests, in this lecture we will be discussing the major themes of Anatomy & Physiology. Themes which we will be exploring in a lot more detail throughout not only biology 131, but also in biology 132. For right now, however, it is essential to gain a general understanding of these important ideas so that we CAN explore them together in more detail in the future. Since this IS a biology course, Biology 131: Human Biology I, let’s start with that. Do you know what biology is? Can you provide a definition? Simply put, biology is the study of life. But what is the definition of life? Even as children we know that a tree is alive and a rock isn’t. But why? Why are we considered alive, but the chair we are sitting on is not? Can you provide a definition of life? Take a few seconds and give it a try. You’re probably realizing that it’s trickier than you might first think. Isn’t it? “Life” is too complex to be able to provide a simple, one-sentence definition. Rather, life is recognized by what living things do. Your text book names 8 properties that are used to distinguish living things from non-living things. One of the most important properties is that ALL living things are composed of cells. Which we will be coming back to discuss in more detail. The other 7 properties can be seen depicted here. Maybe you touched on some of these in your definition of life. Let’s go through them together. Reproduction- when I ask this question in a class- this is usually one of the first properties students correctly identify as a necessary feature of life. The ability to pass genetic information from 1 generation to the next, either by a single cell duplicating itself or by having genes from 2 parents mix to produce an entirely new individual. Reproduction is essential for all biological organisms. Development- involves 2 major processes: growth & differentiation. Keep in mind that we all originated as 1 single fertilized egg. How did we become the complex multicellular organism that we are? That 1 cell reproduced itself many times and we grew in cell number and in size. These cells also underwent differentiation…they began to specialize in a particular task. They became muscles cells, skin cells, nerve cells, and blood cells. We continue to grow and develop throughout our lives -through childhood, adolescence, adulthood, and old age…different at each stage of our life. Metabolism- another incredibly important feature of life and one we will definitely be coming back to repeatedly. I’m sure you have heard the term metabolism, but considering how it is used in everyday life, you may not know the proper definition. Metabolism refers to ALL of the chemical reactions that take place in the body: the build-up of smaller simpler molecules into larger complex ones, as well as, the break-down of these larger complex molecules into smaller simpler ones. These chemical reactions allow us to take in molecules from our environment: from the food that we eat and the water that we drink and the air that we breathe; and chemically change them to provide us with energy or use them to build the structures of our cells. Any of the wastes that are produced by these chemical reactions must be eliminated from the body. For example, carbon dioxide must be breathed out. It is easy to underestimate the number of these chemical reactions taking place in the body, but there is a constant turnover of molecules…nearly ALL of your body has been replaced within the past year. Homeostasis- Keep in mind that living things need order and stability. So although we may encounter changes in our environment, we must have the ability to always maintain stable internal conditions. Such as this rabbit using its long ears to help maintain its body temperature. As we will be discussing later in this lecture, the ability to maintain homeostasis is vital to our survival. Organization- The universe naturally moves toward disorder. Is it easier to throw a deck of cards in the air and have them scatter and make a mess and become random and disorganized? Or is it easier to arrange them so each of the suits are separated and in numerical order like when you first opened them? It takes energy to keep things organized. Just picture trying to keep your house or apartment organized- it takes effort. Living things, unlike non-living things in the universe, have order and structure. Our cells, our bodies, expend huge amounts of energy and effort trying to maintain order. A breakdown in this order usually leads to illness or even death. Evolution- this seahorse can blend into its environment, increasing its chances for survival. Although no single individual evolves over the course of its own lifespan, evolution is incredibly important for the survival of a species. We have all heard of Darwin’s theory of evolution; of his theory of the survival of the fittest. Mutations, changes in the DNA structure, allow variations among individuals of a species which can be passed onto their offspring & may give that species an increased likelihood of being able to survive. Lastly, Responsiveness/Movement- all living things respond to their environment. Whether it is by nerves & muscles like we do- allowing us to move away from something harmful or to move food through our digestive system, to move air in & out of our lungs, or pump blood throughout our body. But even a plant, which we don’t think of as having movement per se, will grow towards the sun and its roots will reach out in the direction of water. Without this ability, we would never survive. Hopefully throughout this semester (& in biology 132) you will gain a greater understanding and appreciation for the importance of these 8 properties and their role in living organisms, particularly humans. Although the title of this course is human biology, we will specifically be studying Anatomy & Physiology- in fact you may have noticed that that is the name of your textbook. So making sure that we have an understanding of what these terms mean is just as important as understanding the definition of biology. Can you define anatomy and physiology? Go ahead and give it a try… Anatomy is the study of structure (or form). Physiology is the study of function The name of your text book is called “Anatomy & Physiology- the unity of form and function” It is extremely important to understand that although anatomy & physiology are 2 different fields of study, they are very much interrelated. What something is capable of doing (its function) is very dependent on its structure (its form). A simple, non-biological example are tools we design to perform a certain task. The structure of screwdriver is very different from the structure of a hammer because they have been specifically shaped to best perform the task they are being used for. Now on occasion, I have been known to use a high heel shoe as a hammer, but lets face it…its not as efficient as a hammer. You will never see a construction worker using a high heel show to build a house. Similarly, structures in the body have certain features because these structures will best be able to carry out the necessary functions. Throughout this semester you should CONSTANTLY be asking yourself- “what is unique & important about this structure? How does its structure relate to its function? What does its structure tell you about its function?” As the semester goes on you will probably tire of hearing me say “structure is function and function is structure”…but take it for what it is… a reminder to always be asking yourself these questions & making these associations. Don’t memorize, but rather understand- why things in the body have the structure they have and how they work the that way they do. Make it make sense! As we study “Human Biology” throughout biology 131 and 132 it is important to recognize that there are different levels at which we can study Anatomy & Physiology; different levels at which we can study the structure and function of the body. This semester we will be starting at the very basic levels and working our way up. Starting at the atomic level and working our way up to the whole organism. I often find that when students enroll in an anatomy & physiology class that they are expecting the entire semester to involve the naming of bones and muscles and they are sometimes disappointed to learn that we will be spending a great deal of time studying what basically amounts to chemistry , as well as, looking as cells and tissues. But we start at the basic levels because it is easier to understand complex systems by studying its simpler components-a theory known as reductionism. And as you have already seen by how difficult it was to even define life; a living organism is an extremely complex system so it is by studying the structure and function of the body at these basic levels that we understand the way the body TRULY works. However, while it may make it easier to understand the whole by looking at the individual parts, bear in mind that whenever you reduce things down to its basic components, you are losing something. Every time we move up to a higher level of organization, look at a larger part- we will see that there are emergent properties. Unique features, properties, capabilities that arise or emerge when the individual parts come together and work together. Therefore, while we will definitely be using reductionism to study the human body, don’t forget about holism. Don’t forget to take a step back and look at how the individual parts work together to become more than they are individually. Because we human beings are definitely more than the sum of our parts! We will be spending a lot more time looking at all of these levels of organization in a lot of detail over the next 2 semesters, but right now I just want to VERY briefly discuss some of the unique features of each level and hopefully underscore the importance of studying biology at all of these different levels of organization. 1st we have the atomic level. Atoms are the smallest particles with unique chemical identities and they are the building blocks of all things- both living and non-living. I’m sure you’ve seen a periodic table at some point in your education, even if you don’t remember much about it. It is essentially a chart of all of the elements that make up matter, each with its own type of atoms. Throughout chapter 2 we will be exploring the atomic level and looking at this periodic table and the major elements needed for life in much more detail, but for right now, it is important to recognize, that even at this level we can see the relationship between structure and function. The number and position of protons, neutrons, and especially electrons, that make up an atom, ultimately lead to the unique properties of each element. Physical properties are those that we can detect with our senses. Such as- color, texture, boiling point, and freezing point. Chemical properties refer to the way atoms interact with other atoms. Bonding behavior- which we will also study in chapter 2. Bonding behavior of atoms is going to be especially important because the bonding of atoms is going to result in the next level of organization… the molecular level. Molecules are two or more atoms held together by chemical bonds. Once again, you can see evidence of how important structure is for function. For example, molecules of morphine are capable of reducing pain because they are capable of binding to receptors (which are also molecules) in our body. They can bind to these receptors, because they fit, like puzzle pieces. Why? Because a portion of the molecule is very similar in structure to the natural endorphins that our body produces. Its structure is the only reason why morphine can fit and thereby bring about its effect. Compounds are a special type of molecule- they are two or more DIFFERENT kinds of atoms chemically bonded together. All compounds are molecules, but not all molecules are compounds. Kind of a “all cocker spaniels are dogs, not all dogs are cocker spaniels” kind of thing. For example oxygen molecules are two atoms of oxygen bonded together. Therefore they are molecules, but not compounds. On the other hand something like sodium chloride- is composed of 2 different kinds of atoms. It is therefore both a compound and a molecule. Sodium Chloride is also a perfect of example of how even at this low level of organization we can see the existence of emergent properties. Sodium Chloride has different characteristics than sodium or chlorine. When the metal sodium combines with the toxic gas chlorine it becomes edible sodium chloride- table salt, which as long as we don’t have high blood pressure, is perfectly safe to be dumping all over our food and ingesting. Sodium Chloride is a small and simple molecule, but some molecules can become quite large- called macromolecules- we will be studying 4 macromolecules that are extremely important to the body in chapter 2 as well. Next, we will spend all of chapters 3 and 4, exploring the cellular level. Discussing the structure and functions of the cell. We will see how both small and large molecules interact with each other to form organelles- which you can think of as the tiny organs of the cell- each with its own structure which help the cell carry out its major functions. At this level of organization we will finally actually studying biology. Why? Because as this level we have an incredibly important emergent property - life!! We said 1 of the 8 major properties of living things is that they are composed of cells. Anything composed of at least 1 cell is alive. Anything alive must be composed of at least 1 cell. Single-celled organisms are alive and cells are also the “building blocks” for multicellular organisms. Although all cells have some common structures and functions, individual cells have quite a lot of variability. Each cell type has its own unique structures to help it best carry out its particular functions. Structure is function & function is structure! Just some examples of different cell types, each with their own unique structures & functions that we will be seeing in the future: Red blood cells- the only cells in the human body which do not have the organelle called a nucleus. The nucleus is the control center of a cell, but RBCs sacrifice it, dump it out of the cell, to make more room for hemoglobin in order to be able to best do its assigned task…transporting oxygen. Not having a nucleus also allows it to better squeeze through the tiny little blood vessels in the body. Muscle cells- have the ability to contract, to cause movement. There are different types of muscle cells- skeletal, smooth, cardiac- each with their own properties, which we will be discussing. Skeletal muscles, for instance, are very large, multi-nucleate cells. Why? Because early on during development many cells fused together, each donating their organelles- including their nucleus- to make one much larger cell Nerve cells- capable of sending electrical signals to, from, and within the brain and spinal cord. They have a lot of processes- axons and dendrites- which can send and receive information. Some of these processes can extend for several feet, reaching from the spinal cord all the way out to our finger or toes. Sperm cells- the only cell in the human body with a flagella – capable of propelling the cell. A feature much more common in single-celled organisms. Epithelial cells- packed close together found on the surfaces of the body- both external and internal. Helping to provide a barrier to protect us from harmful things found in the environment. When groups of similar cells work together to carry out a common function we are looking at …. the tissue level. There are 4 major tissue types, each with their own structure and function: Connective, Epithelium, Muscle, and Nervous Tissue. The first lab module will be focusing on these 4 major tissue types as well as the many different subtypes; which are found in Chapter 5 of the text book. When a structure is composed of at least 2 tissue types we have the … the organ level. The heart, the brain, the lungs, the liver, the kidneys…there are so many examples. Since these structures are composed of at least 2 different tissue types and usually all 4 different tissue types- they are capable of extremely complex functions. For example, let’s look at the stomach: The inside lining is epithelial tissue that produces digestive juices while the bulk of the stomach wall is muscle tissue which churns and mixes food. Connective tissue reinforces the soft muscular walls, and nerve fibers regulate digestive activity by controlling muscle contraction and the production of digestive juices by glands. When organs work together to accomplish a common purpose, they are part of … the organ system level. After we focus on chemistry (the atomic & molecular levels) in chapter 2, and cell structure and functions in chapters 3 and 4, and tissues in the lab portion of this course in chapter 5 we will be moving on to chapters about organ systems. Chapter 6 will cover the integumentary system, looking at the important roles of skin, hair, and nails. Chapters 7 & 8 will focus on the skeletal system, looking at the importance of not only bones, but cartilage and ligaments as well. Chapters 9 & 10 will explore the muscular system, focusing primarily on skeletal muscle, but also looking briefly at smooth muscle (which is found in a lot of our internal organs such as our digestive system) and cardiac muscle (which is found in the heart). And then we will spend 4 chapters (12, 13, 14, and 15) looking at the importance of the nervous system. In Biology 132 you will then focus on the remaining organ systems- the endocrine, cardiovascular, lymphatic, urinary, digestive, respiratory, and reproductive systems. (found in the second half of the textbook- yes, the good news is that you use the same expensive textbook for both biology 131 and 132- so don’t sell it immediately after completing 131…you WILL need it again!!) And this finally brings us to the highest level of organization… the organismal level. The organism represents the sum total of ALL structural levels working together to promote life. And remember the ideal of holism we discussed…we are more than the sum of our parts! It is important to keep in mind as we go through the semester and study the human body at all of these different levels of organization, that we will always be talking about the “typical” structures, the quote unquote “average human”. But no 2 humans are exactly alike. We are all unique. We all show variation. Differences can exist because of sex, age, diet, weight, and level of physical activity. Take a look at the descriptions for an average man or woman. You don’t need to memorize these values, but it is important to realize that descriptions of structure, values, & measurements listed throughout the book are referring to the average, but there is a great deal of variation from one person to the next. Now that we have defined biology and listed the 8 major properties necessary for life, as well as defined anatomy & physiology and discussed the different levels at which we can and will study the structure and function of the body… lets finish up this lecture by returning to one of those 8 major properties of life and discussing it in more detail: Homeostatsis The literal translation of the word homeostasis is “unchanging”. But that term is inaccurate and misleading. Remember that we said earlier in this lecture that homeostasis is the ability to maintain stable internal conditions, regardless of the outside environment. To do so actually requires constant changes, small fluctuations that maintain a balance. Therefore the body is said to be in a state of dynamic equilibrium. Virtually every organ system in the body plays a role in homeostasis. But for equilibrium to be maintained, communication within the body is essential and is accomplished by the nervous system (which uses electrical impulses) and the endocrine system (which used blood borne chemicals called hormones) which makes these 2 systems particularly important. A homeostatic control system consists of 3 interdependent components: The receptor- which monitors the environment and detects to changes/imbalances (which we call stimuli). It sends information through the afferent pathway (afferent with an “A”) to the Control center- the control center determines the “set point” the ideal value at which we want that variable to be maintained. The control center will compare the incoming information from the receptor to the ideal set point and determines if an action needs to be taken. It will then send information out through the efferent pathway (efferent with an “E”) to an Effector- an effector has the ability to bring about the desired effect, the desired change, returning the variable to the desired ideal, returning the body to equilibrium, maintaining balance, restoring homeostasis. Temperature stability is a perfect example of maintaining dynamic equilibrium. Let’s forget about the human body for a minute and look at temperature in a way we are more familiar with- room temperature….in your house, apartment, or office. The thermostat in this case is the control center- it determines the set point- the ideal. Maybe you want to set it for 68 degrees. Keep in mind that the temperature of a room fluctuates, it is never exactly what you set it for (68 degrees in this example) maybe it may be as high as 70 or as low as 66. It is NOT “unchanging” it is constantly changing, but trying to maintain the optimal temperature. If the temperature gets too low, this acts as a stimulus. A stimulus that is detected by the receptor- which in this case is the thermometer. The thermometer sends this information to the control center (the thermostat) via the afferent pathway-the thermostat compares the current temperature to the ideal & makes a “decision” that it is too far away from the set point, the temperature is too low. The thermostat sends information to the effector, the heater in this case, via the efferent pathway and signals it to kick on. The heater is the effector because it brings about the desired effect- in this case raising the temperature. Once it is on it will probably overshoot the desired temperature by a little bit. Maybe bring it all the way up to 70 degrees before kicking off. How does it know when to kick off? It kicks off when the temperature gets too high. In this example the receptor is once again the thermometer. It is responding to the increase in temperature; the stimulus. It sends information regarding the temperature to the control center (the thermostat) via the afferent pathway, which compares the current temperature to the ideal. Once again it makes a “decision” this time that the room temperature is too high compared to the set point. The thermostat sends information to the effector, the heater, via the efferent pathway and this time signals it to turn off. Hopefully by turning off the heater the room temperature will now decrease. In this way the heater cycles on and off and the temperature is always fluctuating, but the temperature is remaining close to the ideal temperature that you desired. The body is much the same. We all know the ideal body temperature is 98.6 degrees (at least for the average person), but in reality the body temperature is always fluctuating some- trying to maintain this ideal temperature. If the temperature gets too high, what does the body do to lower it? It will cause your blood vessels to dilate, bringing the blood closer to the surface of the body allowing more heat to escape and if we get too hot we will start to sweat. If the temperature gets too low, what does the body do to raise it? It causes blood vessels to constrict, reducing the loss of heat from the skin and if we get too cold we will start to shiver to produce more heat. Dynamic equilibrium. A relatively stable internal environment regardless of the outside environment, at least up to a certain point. Most homeostatic control mechanisms are negative feedback mechanism. By negative we don’t mean “bad”. We mean that it causes the variable to change in the opposite direction to that of the initial change; The output shuts off the original stimulus; it attempts to return the variable to the “ideal” value. If something gets too high- a negative feedback mechanism will lower it If something gets too low- a negative feedback mechanism will raise it Dynamic equilibrium- constantly fluctuating, but always trying to maintain a happy medium. The body is constantly trying to maintain homeostasis, trying to achieve a happy medium. So controlling body temperature is just 1 of many, many examples of negative feedback mechanisms. Let’s look at another example: Blood Pressure. I’m sure you have had the experience of getting up too fast and feeling a little light headed or dizzy. This is a result of a quick drop in blood pressure. It’s actually amazing that we only get this light headed feeling every once in a while. In fact it’s actually an impressive feat of the body that we don’t simply pass out every time we stand up. When you are horizontal the heart is not having to work against gravity to get blood to you head, but when you stand gravity is suddenly helping to quickly drain the blood from you head and the heart is now having to pump the blood against gravity to have it reach your head. This drop in blood pressure, this decrease in blood flow to the brain, could have disastrous consequences if not corrected for. So once again our body uses receptors, in this case pressure receptors called baroreceptors which are embedded in the walls of blood vessels above the heart, to detect this drop in blood pressure that occurs when we stand. These receptors send information via the afferent pathway to the control center (in this case the cardiac center in the brainstem) which compares the blood pressure to the set point, the ideal value, and determines that the blood pressure is too low. It then sends information to the effector, in this case the heart, via the efferent pathway and signals the heart to speed up, which raises the blood pressure, restoring homeostasis. If these feedback mechanism doesn’t respond quickly enough, doesn’t restore homeostasis fast enough, as occurs more commonly in the elderly, then a person WILL get light headed and dizzy and may even faint. In addition to blood pressure and body temperature, the body also uses negative feedback mechanisms to control the rate and depth of breathing, the levels of oxygen, carbon dioxide, & nutrients in the blood, and even the withdrawal reflex is an example, which occurs when we touch something painful- if it is sharp or hot- and we pull back our hand or our foot. Can you think of any other examples of things that are probably controlled by negative feedback mechanisms in the body? In addition to negative feedback mechanisms; the body also sometimes uses positive feedback mechanisms. Once again the word positive does not mean “good” but rather it refers to the fact the output enhances the original stimulus so the output is accelerated. It causes the variable to change in the same direction to that of initial change. If something gets too high- a positive feedback mechanism will continue to raise it even more If something gets too low- a positive feedback mechanism will continue to lower it even more In other words rather than restoring homeostasis, positive feedback mechanisms cause the body to move further away from equilibrium, further away from the happy medium. As a result they are often referred to as cascades because once initiated they are self-perpetuating and have an amplifying effect. Given what we have just described, it is not surprising that positive feedback mechanisms are not nearly as common as negative feedback mechanisms. They usually control infrequent events that do not require continuous adjustments. Even though positive feedback mechanisms are not used as frequently as negative feedback mechanisms, they still play an important role in the body. In some instances causing the body to move away from equilibrium, bringing about some kind of change, is ok for a time and can even be helpful. Blood clotting and labor contractions are both examples of the body using positive feedback mechanisms. When we are injured and bleeding we want to minimize blood loss, we want to stop the flow of blood. As we will discuss in more detail in biology 132 this is achieved partly by blood cells called platelets attaching to the damaged tissue and releasing chemicals which attract more platelets, which release more chemicals, which attract more platelets…and so on. When a woman goes into labor the head of the baby pushes against the cervix, which results in the release of a chemical called oxytocin, which stimulates the uterus to contract, which causes the baby to push against the cervix, which causes more oxytocin to be released, which increased contractions…and so on. The use of positive feedback mechanisms to create these amplification effects in blood clotting and labor contractions are useful and necessary functions for a period of time. But we certainly don’t want to have all of our blood clot and I think most women would agree that they would REALLY prefer to not be in labor for the rest of their lives… so we don’t want these actions to continue indefinitely. We want them to occur long enough to bring about the desired change and then stop! Because positive feedback mechanisms are self-perpetuating, have an amplifying effect, and bring the body away from equilibrium they can be harmful and even life-threatening. For example, when our body is fighting off an infection it can be beneficial for the body temperature to rise to a certain extent. But it the temperature gets too high it can be extremely dangerous. As the body temperature rises, it increases metabolism, higher metabolism (more chemical reactions) in turn raises the temperature, which raises metabolism, which raises temp…leading to a vicious cycle. A dangerous cycle, which if not corrected can lead to seizures, coma, and even death. Remember that ultimately, homeostasis is one of the 8 major properties of life. Physiology, the functioning of the body, is largely a group of mechanisms for maintaining homeostasis and the loss of homeostatic control is often the cause of illness and death. We can bring the body away from equilibrium for a time to bring about change, but if equilibrium is not restored and maintained, life cannot continue to exist. That brings us to the end of this lecture. On this last slide you will find a list of the chapter objectives. Before attempting the lecture exam at the end of this module, you should make sure that you have achieved these objectives. If you have any questions, comments, or concerns about these objectives or any anything we have gone over in this packet, please post your questions, comments, or concerns in the discussion forum where I and other students can respond and attempt to clear up any confusion. Or you can email me directly if you prefer. Don’t forget to be working on the Learn Smart Assignment for this chapter. Have a good day!