Body Systems Revised THIRD EDITION REDESIGNED FOR THE NGSS ISSUES AND LIFE SCIENCE
Body Systems Revised THE LAWRENCE HALL OF SCIENCE UNIVERSITY OF CALIFORNIA, BERKELEY THIRD EDITION REDESIGNED FOR THE NGSS ISSUES AND LIFE SCIENCE
This book is part of SEPUP’s Issues and Science 17-unit multi-year course. The units are designed to allow for custom sequencing to meet local needs. For more information about these units, see the SEPUP and Lab-Aids websites listed at the bottom of this page. • Land, Water, and Human Interactions • Geological Processes • Earth’s Resources • Weather and Climate • Solar System and Beyond • Ecology • Body Systems • From Cells to Organisms • Reproduction Additional SEPUP instructional materials include: • SEPUP Modules: Grades 6–12 • Science and Sustainability: Course for Grades 9–12 • Science and Global Issues: Biology: Course for High School Biology This material is based upon work supported by the National Science Foundation under Grants 9554163 and 0099265. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. For photo and illustration credits, see page 118, which constitutes an extension of this copyright page. The preferred citation format for this book is SEPUP. (2020). Issues and Life Science: Body Systems. Lawrence Hall of Science, University of California at Berkeley. Lab-Aids, Inc. Body Systems - Student Book, Revised Third Edition | Redesigned for the NGSS © 2020 The Regents of the University of California ISBN: 978-1-63093-616-7 v1 SMS-BOD-3RSB Print Number: 01 Print Year: 2020 Developed by Lawrence Hall of Science University of California at Berkeley Berkeley, CA 94720-5200 website: www.sepuplhs.org Published by 17 Colt Court Ronkonkoma, NY 11779 Website: www.lab-aids.com • Evolution • Biomedical Engineering • Energy • Chemistry of Materials • Chemical Reactions • Force and Motion • Fields and Interactions • Waves
v ISSUES & LIFE SCIENCE THIRD EDITION Director: Ben W. Koo Director Emerita: Barbara Nagle Coordinator: Janet Bellantoni AUTHORS Maia Binding, Barbara Nagle, Manisha Hariani OTHER CONTRIBUTORS Donna Markey, P. Terese Lang, Susan K. Boudreau CONTENT AND SCIENTIFIC REVIEW Dr. Giulia Gurun, Lecturer of Molecular, Cell, and Developmental Biology, University of California at Santa Cruz, Santa Cruz, CA PRODUCTION Coordination, Design, Photo Research, Composition: Seventeenth Street Studios Production Coordinator for Lab-Aids: Hethyr Tregerman Editing: Kerry Ouellet and Jennifer Davis-Kay
vi FIELD TEST CENTERS The classroom is SEPUP’s laboratory for development. We are extremely appreciative of the following center directors and teachers who taught the program during the 2003–04 and 2004–05 school years. These teachers and their students contributed significantly to improving the first edition of the course. Since then, Issues and Life Science has been used in thousands of classrooms across the United States. This third edition is based on what we have learned from teachers and students in those classrooms and in the Revision Centers listed on the next page. It also includes new data and information, so the issues included in the course remain fresh and up-to-date. REGIONAL CENTER, SOUTHERN CALIFORNIA Donna Markey, Center Director Kim Blumeyer, Helen Copeland, Pat McLoughlin, Donna Markey, Philip Poniktera, Samantha Swann, Miles Vandegrift REGIONAL CENTER, IOWA Dr. Robert Yager and Jeanne Bancroft, Center Directors Rebecca Andresen, Lore Baur, Dan Dvorak, Dan Hill, Mark Kluber, Amy Lauer, Lisa Martin, Stephanie Phillips REGIONAL CENTER, WESTERN NEW YORK Dr. Robert Horvat, Center Director Kathaleen Burke, Dick Duquin, Eleanor Falsone, Lillian Gondree, Jason Mayle, James Morgan, Valerie Tundo JEFFERSON COUNTY, KENTUCKY Pamela Boykin, Center Director Charlotte Brown, Tara Endris, Sharon Kremer, Karen Niemann, Susan Stinebruner, Joan Thieman LIVERMORE, CALIFORNIA Scott Vernoy, Center Director Rick Boster, Ann Ewing, Kathy Gabel, Sharon Schmidt, Denia Segrest, Bruce Wolfe QUEENS, NEW YORK Pam Wasserman, Center Director Gina Clemente, Cheryl Dodes, Karen Horowitz, Tricia Hutter, Jean Rogers, Mark Schmucker, Christine Wilk TUCSON, ARIZONA Jonathan Becker, Center Director Peggy Herron, Debbie Hobbs, Carol Newhouse, Nancy Webster INDEPENDENT Berkeley, California: Robyn McArdle Fresno, California: Al Brofman Orinda, California: Sue Boudreau, Janine Orr, Karen Snelson Tucson, Arizona: Patricia Cadigan, Kevin Finegan
vii REVISION CENTERS Chicago, Illinois: Bejaza Duskic, Robert Troher Elmhurst, Illinois: Kelly Biala
viii A Letter to Issues and Science Students As you look through this book, you may wonder, “Why does this book look different from other science textbooks I’ve seen?” The reason is simple: It is a complete science program, and only some of what you will learn can be seen by leafing through these pages! SEPUP is an active learning program. Through hands-on laboratories, investigations, readings, simulations, scientific debates, role plays, and design projects, you will develop your thinking about science and engineering and how they relate to many important issues facing our society today. In this program, you will think scientifically about natural phenomena or observable events. For example, you might investigate why most people look unique but also look more like their biological relatives than they look like most other people. Or perhaps you will model how a change in a river’s path due to natural processes, which can then change the landscape and impact human-made structures. The activities in this course provide many opportunities for you to figure out why or how something happens. Like a scientist, you’ll begin by asking questions and analyzing evidence to help you create explanations and models. Like an engineer, you will solve specific problems by designing a solution—for example, designing a model of an artificial heart valve for a person with advanced heart disease. This program will ask you to think about issues at the intersection of science and society. You may consider how to create a mechanical system to help drivers maintain a safe distance behind other cars, or debate the trade-offs of using different materials (aluminum, glass, or plastic) to make a water bottle. You’ll improve your decision-making skills by using evidence and analysis to make the best decision about what should be done for a community, such as deciding where to mine for valuable resources like copper while minimizing environmental impact. You’ll consider the influence of science, engineering, and technology on societal issues, and what role scientists, engineers, and citizens play in the decision-making process. How do we know that this is a good way for you to learn? Because most research on science education supports it. Many activities in this book were tested by hundreds of students and their teachers. Their feedback, and what we’ve learned about how people develop an understanding of science, has informed the SEPUP approach. We believe the SEPUP program will show you that learning about science and engineering is important, enjoyable, and relevant to your life. SEPUP Staff
ix 1 v i e w a n d r e f l e c t The Pellagra Story 3 2 m o d e l i n g Parts of a Whole 7 3 i n v e s t i g at i o n What’s Happening Inside? 11 4 r e a d i n g Digestion: An Absorbing Tale 15 5 m o d e l i n g Food Breakdown 21 6 l a b o r at o r y Observing Organisms 25 7 l a b o r at o r y Can You Feel the Difference? 29 8 r e a d i n g Finding the Nerve 35 9 l a b o r at o r y Heartily Fit 41 10 l a b o r at o r y Gas Exchange 47 11 r e a d i n g Interacting Systems 53 12 m o d e l i n g The Circulation Game 61 13 i n v e s t i g at i o n Testing Medicines: A Clinical Trial 67 14 ta l k i n g i t o v e r Evaluating Clinical Trials 71 Unit Summary 75 Appendices 79 Glossary 112 Index 115 Credits 118 Contents Body Systems Revised
Body Systems
Sa r a is always tired and hungry after basketball practice, but as soon as she has a snack, she’s got more energy. She asks her friend Adel, “Why do you think healthy food gives us energy? I mean, what actually happens in my body when I eat my peanut butter crackers?” Adel says, “I know that our stomachs break down the food. I wonder if that means it’s broken down into really small pieces that can move into the rest of our body. Do you think those pieces have energy our bodies can use?” “Maybe.” Sara thinks for a moment. “And I bet that different foods have different amounts of energy, because I get more energy from peanut butter crackers than from plain crackers!” • • • In this unit, you will: • Explore phenomena related to how body systems interact and function in a healthy person and when a person is sick. • Develop and use models to explore how your body turns food into energy that your body can use • Gather and make sense of information about how your body sends and receives messages to help it function • Develop explanations of how your body systems work together and what happens when a system is not working properly • Investigate the issue of how interactions between body systems can be affected by disease, medications, and other factors
BODY 3 1 The Pellagra Story v i e w a n d r e f l e c t Collecting evidence is an important aspect of science. One way to collect evidence is to conduct experiments. For example, if a neuroscientist (someone who studies nervous systems) wants to understand the nervous system of a worm, the neuroscientist would test many worms and repeat the same procedure multiple times. A doctor working to develop an artificial heart for people would use a different approach, and not test the artificial heart in people right away. What kinds of experiments are possible when you study human beings? How can you collect evidence in these situations? Begin to consider these issues as you watch the story of a disease called pellagra, which affected poor rural families of the United States South during the early 1900s. You will learn how scientists investigated this disease and its effects on the human body.1 2 3 4 GUIDING QUESTION How do scientists investigate and gather evidence about the human body?5 MATERIALS For each student 1 Student Sheet 1.1, “Observations and Inferences”6 7 8 1 Student Sheet 1.2, “Three-Level Reading Guide: Studying People Scientifically” 1 NGLS1A3 2 NGCCCE1 3 NGCCNS1 4 NGSPNS1 5 NGPEL13 6 NGSPOE1 7 ELRS687 8 ELRS689 Scientists didn’t know why pellagra was more likely to affect rural families of the South.
ACTIVITY 1 THE PELLAGRA STORY 4 BODY PROCEDURE Part A: Viewing the Pellagra Story 1. To prepare to watch the video, read Analysis items 1–3. 2. Watch the video about Dr. Goldberger and pellagra. 9 3. Discuss the following questions with your group:10 11 12 • What was the problem of pellagra?13 • What four things did people think caused pellagra? • What evidence did Dr. Goldberger observe or collect about pellagra? • What did Dr. Goldberger conclude about the cause of pellagra?14 4. Complete Student Sheet 1.1, “Observations and Inferences,” and discuss your responses with your class.15 Part B: Studying People Scientifically16 17 18 Refer to Student Sheet 1.2,“Three-Level Reading Guide: Studying People Scientifically,” to guide you as you read. You will complete this sheet after you’ve read the following passage.19 Studying people scientifically presents some interesting challenges. One challenge is that people react differently to identical events. How do scientists deal with this type of challenge? Scientists usually begin with an idea about what they want to investigate. This is also true for scientists who study people. This idea, or hypothesis, is the basis for their study. A hypothesis is an explanation based on observed facts or on an idea of how things work. For example, Dr. Goldberger hypothesized that there was a relationship between pellagra and diet. After coming up with a hypothesis, scientists make observations and collect data. An observation is something the scientist sees or notices. For example, Dr. Goldberger might have noticed that one of his patients looked tired. Data are facts. For example, the patient might state that they slept only two hours the previous night. Scientists hope that these data will provide evidence for testing their hypothesis. They may collect the data through experiments or other types of research. Scientists use these data to make inferences. An inference is a conclusion made based on what is known. 9 NGCCNS1 10 NGSPOE1 11 NGSPNS1 12 ELRS687 13 NGPEL13 14 NGCCCE1 15 ELRS689 16 NGCCNS1 17 NGSPNS1 18 ELRS689 19 SELTTL1 Dr. Joseph Goldberger
THE PELLAGRA STORY ACTIVITY 1 BODY 5 The results of research can provide evidence that supports or refutes a hypothesis. In some cases, an experiment provides new information. This new information can lead to another hypothesis and another experiment or investigation. In this way, a hypothesis can be a “work in progress” that is continually revised. In the United States, government agencies tightly control and review products planned for use on humans. One such agency is the Food and Drug Administration (FDA). To be approved for public use, a product must undergo and pass scientific tests. New medicines are usually first tested on animals to see whether the medicines cause any harmful side effects. Human volunteers take part in the next phase of testing, known as clinical trials. The results of clinical trials must show that the medicine or medical device is both safe and effective before it can be approved for use by the public. Today, modern clinical trials address the rights of the people who agree to participate. This was not always the case in Dr. Goldberger’s time. Volunteers are now chosen carefully. They must not be allergic to drugs similar to the one that will be tested. Also, they cannot be taking certain other medicines. These things might make it more likely for them to experience harmful side effects. The volunteers must be told about any risks, such as possible side effects. They sign an informed consent form, which states that they have been told (informed) about the risks and that they agree (consent) to participate in the trial. This helps ensure that the volunteers are freely choosing to take part and know what they may encounter during the clinical trial. Medical products, such as hearing aids, pacemakers, and contact lenses, are tested before being sold to the public.
ACTIVITY 1 THE PELLAGRA STORY 6 BODY ANALYSIS 1. What was the first step in Dr. Goldberger’s research into pellagra? Explain why this step was important in developing his hypothesis. 20 2. Revisit the issue: Think about the relationship between pellagra and nutrition. a. What did Dr. Goldberger do to provide evidence of the relationship between pellagra and nutrition? Be sure to explain how his research provided evidence that supported or refuted his hypothesis. 21 22 23 24 b. How could he have provided more convincing evidence of the relationship between pellagra and nutrition? 25 3. To investigate his hypothesis, Dr. Goldberger had prisoners volunteer to be fed a poor diet; as a result, 7 out of 11 prisoners developed pellagra. What do you think about Dr. Goldberger’s decision to experiment on people? Support your answer with evidence, and identify the trade-offs of your decision. 26 27 28 29 30 Hint: To write a complete answer, first state your opinion. Provide two or more pieces of evidence that support your opinion. Evidence is factual information or data that support or refute a claim. Consider all sides of the issue, and identify the trade-offs of your decision. A trade-off is a desirable outcome given up to gain another desirable outcome. 4. Reflection: Would you be willing to participate in a clinical trial? Explain your thinking. EXTENSION For links to more information about Dr. Joseph Goldberger and his war on pellagra, visit the SEPUP Third Edition Body Systems page of the SEPUP website at www.sepuplhs.org/middle/third-edition, and go to “The Pellagra Story.” 20 NGCCNS1 21 NGSPOE1 22 NGCCCE1 23 NGSPNS1 24 NGPEL13 25 NGSPOE1 26 NGSPOE1 27 NGSPEA2 28 ELRS687 29 ELRS689 30 SEASET1
BODY 7 2 Parts of a Whole m o d e l i n g How often do you think about what’s going on inside your body? Most healthy people don’t need to worry about what’s happening inside. But knowing more about the human body can help you make better decisions about your health. Recall a time when you had a stomachache. Knowing that the function of the stomach is to help digest food may have helped you figure out what to do. Perhaps you didn’t eat anything for a couple of hours, or you drank water. When studying the human body, scientists investigate the relationship between a structure (such as the stomach) and its function (helping to digest food). Structures are the parts the body is made of and how the parts are organized. The things a structure does are called its function. 31 32 GUIDING QUESTION What do you know about structures, such as organs, in the human body? MATERIALS For each group of four students 1 sheet of chart paper or butcher paper 4 markers of assorted colors 4 sticks of modeling clay (1 red, 1 blue, 1 green, 1 yellow) 1 human torso model plastic wrap For each student 1 Student Sheet 2.1, “Organs in the Human Body” 31 NGLS1A3 32 NGCCSF1 Doctors listen to organs, such as the heart, to determine what’s happening inside the human body.
ACTIVITY 2 PARTS OF A WHOLE 8 BODY PROCEDURE33 Part A: Laying It Out 34 1. With your group, draw an outline of a human body on a piece of chart paper or butcher paper. Leave room on the paper around your human body outline to write notes. 2. Each student in your group should choose a marker, one different color per student. Work together to do the following: a. Each student draws three different major organs of the body inside the outline. Organs are structures composed of one or more tissues that perform a function or group of functions in the human body. For example, the stomach is one organ that helps your body digest food. b. Each student labels the organs they drew and describes the organs’ functions, writing as close to each organ as possible. c. Around the outline, each student writes questions they have about the human body. 3. Go around the room to view the drawings of other groups. 4. In your science notebook, write down your questions from your drawing of the human body. Add any questions other students asked that you cannot answer. 35 Part B: Modeling the Human Body36 37 5. You are going to make a three-dimensional model of some of the organs and structures of the body. A model is a representation of a system, or its components, that is used to help understand and communicate how a system works. Here you are using a plastic model of a human torso. Place the human torso model on a flat surface. 6. Line the inside of the back half of the human torso model with a piece of plastic wrap. 7. With your group, use the modeling clay to create each organ listed in the table on the following page. Student Sheet 2.1, “Organs in the Human Body,” can help guide you in forming the organs correctly. 38 33 NGCCSM1 34 NGCCSF1 35 ELRS687 36 NGSPDM1 37 NGCCSF1 38 ELRS687
PARTS OF A WHOLE ACTIVITY 2 BODY 9 8. Place the organs into the back half of the human torso model. Place the first structure listed in the table (the muscles), and then add the others in the order listed. Remember to refer to Student Sheet 2.1 for help. Hint: You’ll need to put the end of the digestive system, the large intestine and rectum, behind the bladder to make it accurate. 9. When you are done modeling the organs, place the other half of the plastic model on top of the body. You have now created a model of your internal organs. 10. Compare the placement of the internal organs in the model to your own body. Try to figure out where these organs are in your body. 11. Take your model apart. Roll the modeling clay back into separate balls of each color. Organs and Structures to Model CLAY COLOR ORGANS AND STRUCTURES muscles of back and buttocks spinal cord kidneys (connected to bladder by thin tubes) esophagus stomach small intestine large intestine (and rectum) liver windpipe (trachea) lungs heart bladder rib cage (ribs and sternum)
ACTIVITY 2 PARTS OF A WHOLE 10 BODY ANALYSIS 1. Look at the drawing that you made in Part A. List some structures or organs that were not the right shape or size or were in the wrong place on your original drawing. Explain how you would change them if you redrew the diagram. 39 40 41 2. Look at the questions you recorded in your science notebook after Part A. Answer all the questions that you can. Discuss with your group any that you are still not sure about. What questions does your group still have?42 3. The liver is the largest internal organ of the human body. Was the liver the largest organ in your clay model? Do you think that the other organs you modeled in clay were accurate in size? Why or why not? 43 4. What are some limitations of the clay model you made of the human body in Part B?44 5. Consider the organs and structures listed in the table in the Procedure. Which of these do you think work together to perform a specific function in the human body? Identify the organs that you think work together, and describe what you think they do. For example, the kidneys and bladder work together to remove liquid waste from the human body.45 46 47 48 39 NGSPDM1 40 NGCCSF1 41 NGCCSM2 42 NGSPAQ3 43 NGCCSF1 44 NGSPDM1 45 NGPEL13 46 NGLS1A3 47 NGCCSF1 48 NGCCSM2
BODY 11 3 What’s Happening Inside? i n v e s t i g at i o n I n the “Parts of a Whole” activity, you modeled several different organs in the human body. Several organs working together to perform a function are called a system. These levels of structures— tissues forming organs and organs forming a system—are referred to as levels of organization in your body. One example of these levels of organization can be found in the excretory system. The function of the excretory system is to remove liquid waste from the body. Because the kidneys help perform this function, they are organs in the excretory system. The kidneys are made of different kinds of tissues. Each tissue is made of cells. A cell is the smallest structural unit that makes up all living things. You may be familiar with the levels of organization of other body systems, such as the digestive and cardiovascular systems. In this activity, you will use your knowledge of the human body to look more closely inside yourself. 49 50 GUIDING QUESTION How do structures in the human body interact to perform a specific function? 51 52 49 NGLS1A3 50 NGCCSF1 51 NGPEL13 52 NGPEL13 3842 T-7-1 (Body Systems) SB Figure: T-7-1 Fig15_01 Legacy Sans Std Med 10/11.5 kidneys bladder urethra ureters Excretory System
ACTIVITY 3 WHAT’S HAPPENING INSIDE? 12 BODY MATERIALS For each group of four students 1 set of Organ or Structure Cards 1 set of Body System Cards 1 set of Organ Function Cards For each student 1 Student Sheet 3.1, “Functions of Human Body Systems” PROCEDURE 1. Spread out the Organ or Structure Cards on a table. 2. With your group of four, classify the Organ or Structure Cards into systems. Work together to agree on the organs that make up each system. 53 54 • Listen to and consider the explanations and ideas of other members of your group. • If you disagree with your group members about how to classify an organ, explain why you disagree. 3. In your science notebook, write down the groups of organs that you organized into systems. Also write down the name of any organ whose function you are not sure of. 4. Talk over with your group what you think the function of each system is, and record it in your science notebook. 55 5. Discuss with the class your grouping of organs into systems. Observe the similarities and differences between your systems and those of other groups in the class. 56 6. Get a set of Body System Cards from your teacher. Compare the cards’ placement of organs in different body systems, based on their function, with your own grouping system. Rearrange your grouping of organs, if necessary, and record your changes in your science notebook.57 58 7. Get a set of Organ Function Cards from your teacher. Each card describes an organ and its function within a system. Match the Organ Function Card with the organ it describes.59 60 53 NGCCSF1 54 ELSL081 55 ELSL081 56 ELSL081 57 NGLS1A3 58 NGLS1A3 59 NGLS1A3 60 NGCCSF1
WHAT’S HAPPENING INSIDE? ACTIVITY 3 BODY 13 8. Use all three sets of cards to complete Student Sheet 3.1, “Functions of Human Body Systems.” 61 9. Check your answers with your teacher. 10. Look at the grouping of organs that you recorded in Procedure Step 3. Use Student Sheet 3.1 to write down the function of each organ system. ANALYSIS 1. Copy the table headings below. You will add more rows as you complete items 1a–c. 62 63 Organ or Structure System Function a. Fill in the first column with the organs or structures listed in the “Organs and Structures to Model” table in the “Parts of a Whole” activity. b. In the second column, identify the system that matches each organ or structure. For example, the stomach is a part of the digestive system. c. In the third column, identify the function of each organ or structure. 2. Imagine that a younger student did not understand the difference between the body’s organs and its systems. Explain this relationship in a way that a younger student could understand. 64 65 3. Just as all the organs in a system work together, the various body systems work together in a healthy person. Can you think of an example of how two systems work together? Explain your ideas.66 67 68 69 61 SELTDA1 62 NGLS1A3 63 NGCCSF1 64 NGLS1A3 65 NGSPCE1 66 NGPEL13 67 NGLS1A3 68 NGPEL13 69 NGCCSM1
ACTIVITY 3 WHAT’S HAPPENING INSIDE? 14 BODY EXTENSION To find out more about the human body and its systems, visit the SEPUP Third Edition Body Systems page of the SEPUP website at www.sepuplhs.org/middle/third-edition, and go to the suggested resources for this activity.
BODY 15 r e a d i n g I n the activity “The Pellagra Story,” you learned about a serious disease, pellagra, caused by not getting the right vitamins and nutrients in your diet. But how does your body access those nutrients? Your digestive system is responsible for the breakdown of food to get nutrients. Everything you eat and drink, including medicines, enters your body through this system. You can probably name a lot of the organs that food passes through, such as the esophagus, stomach, small intestine, and large intestine. Other organs, like the liver and pancreas, also help your digestive system function, even though food does not pass through them. What happens as food travels through your body? To understand this question, you will consider what happens at a range of scales, from cells to organs and systems. 70 71 GUIDING QUESTION How does your digestive system function and interact with other systems in your body? PROCEDURE 1. Read the text on the following page. 2. Follow your teacher’s instructions for how to use the Stop to Think questions. 7273 70 NGCCSM1 71 NGLS1AA3 72 ELRS684 73 SELTST1 4 Digestion: An Absorbing Tale
ACTIVITY 4 DIGESTION: AN ABSORBING TALE 16 BODY READING Food Breakdown74 Take a moment to look at the diagram of the digestive system below. You can think of your digestive system as a long tube that goes through your body. Food is broken down and nutrients are absorbed along this tube. If your body didn’t absorb what it needed from the food you eat, everything you swallowed would come out the other end! You know that doesn’t happen, but do you know why? What are the functions of each part of your digestive system? How does this system interact with other systems in the body? The digestive system breaks down food into forms that the body can absorb. This process of breaking down food is called digestion. This breakdown occurs two ways—mechanically and chemically—and it begins in your mouth. Your teeth begin the process of mechanical breakdown when you chew. Chewing uses your skeletal system (your jaws and skull) and your muscular system. Chemicals in your saliva begin the process of chemical breakdown. 74 NGLS1A3 salivary glands liver bile duct gallbladder stomach pancreas small intestine large intestine rectum anus esophagus Human Digestive System
DIGESTION: AN ABSORBING TALE ACTIVITY 4 BODY 17 As you swallow, food travels down through your esophagus, which is a tube surrounded by muscle. This muscle contracts to help food reach your stomach, a large bag-like organ. Muscles in your stomach wall help to mix the stomach contents. This continues the process of mechanical breakdown. In your stomach, hydrochloric acid and other chemicals continue the chemical breakdown of food. The hydrochloric acid in your stomach is so powerful that your stomach is lined with mucus to protect itself. When this lining is absent, ulcers (sores in the lining of the stomach) can form. A high level of hydrochloric acid causes the burning sensation you may feel when you vomit or have indigestion. STOP TO THINK 1 a. How does your mouth contribute to the process of digestion? b. How do organs work together to accomplish the function of the digestive system? By the time food reaches your small intestine, you wouldn’t recognize it anymore! It is a thick, pasty mixture. Your small intestine then completes the process of chemical breakdown with help from your pancreas and liver. As food comes into your small intestine from your stomach, it contains high levels of acid. Your pancreas produces a chemical that reduces this acid level. It also produces chemicals that help break down the proteins and fat found in food. Your liver produces bile, an important mixture that helps break down fat. All of these chemicals combine with the partly broken-down food as it travels down your small intestine. Absorption of Nutrients7576 Most of the substances produced by the digestion of food are absorbed into your blood in the small intestine. In the process of absorption, the digested food particles (or nutrients) leave your digestive system and move into your circulatory system through a network of tiny blood vessels (capillaries) just under the lining of your small intestine. The nutrients dissolve in your blood stream and are moved in the blood through your circulatory system, delivering nutrients to the rest of your body. Nutrients are required by every cell in all of the systems of the body. Without a proper balance 75 NGLS1A3 76 NGLS1A3
ACTIVITY 4 DIGESTION: AN ABSORBING TALE 18 BODY of nutrients, you can develop serious diseases, like pellagra, or other medical conditions. With pellagra, the skin and nervous systems are affected. Other conditions affect other systems. The blood acts as the transport vehicle for nutrients after food is digested and nutrients are absorbed. Individual cells and tissues in the various systems of your body can take in the nutrients they need from the blood as it passes by.77 7879 STOP TO THINK 2 a. Explain the relationship between food and nutrients. b. How do your digestive system and circulatory system work together to get nutrients to your body? The fact that most of the final chemical breakdown and nutrient absorption occurs in your small intestine may help explain its length. The average adult small intestine is 5–6 meters (about 15–18 feet) long! This length, plus the folds in the wall of the small intestine, shown in the following illustration, provides lots of surface area for nutrient absorption. Your blood transports these nutrients to different parts of your body, but first it makes an important stop. All the blood that leaves your stomach and intestines goes directly to your liver—through a specialized network of blood vessels—before traveling throughout the rest of your body. In addition to producing bile, the liver performs two other important functions related to digestion. First, it breaks down substances such as alcohol and some medicines. If you’ve taken certain medicines, such as a painkiller for a headache, your liver actually changes the medicine into a form your body can use. But too much medicine can damage your liver. Your liver helps to filter out substances from your blood that could be dangerous to your body, before the blood circulates in the rest of the body. The second important function of the liver is to process nutrients into forms that are easier for the rest of your body to use. For example, your liver stores carbohydrates. Carbohydrates are the sugars, starches, and fiber found in the food you eat. When you suddenly need energy, your liver converts these carbohydrates to sugars that your body can use. Once blood has gone through your liver, it carries the nutrients you 77 SELTST1 78 NGLS1A3 79 NGCCSM1 When doctors diagnose patients, they often ask questions about the patients’ diets. Many medical conditions are linked to how healthy our diets are.
DIGESTION: AN ABSORBING TALE ACTIVITY 4 BODY 19 need to the rest of your body through the circulatory system. After your blood moves through your body, it is filtered by your kidneys. The kidneys excrete liquid waste (urine), which contains unwanted substances, such as excess minerals or salts. STOP TO THINK 3 Why does blood travel to your liver before transporting nutrients to other parts of your body? Getting Rid of Solid Waste808182 Any material that has not been absorbed in your small intestine continues down into your large intestine, or colon. Your muscular system helps the large intestine move this material. In your large intestine, large quantities of water and some remaining vitamins are absorbed into your blood. The remaining unabsorbed material forms solid waste as it travels through the large intestine, a process that can take 18–24 hours. This solid waste is temporarily stored in the rectum before being pushed out through the anus. What is this solid waste 80 NGLS1A3 81 NGCCSM1 82 NGCCSM1 Seventeenth Street Studios Science and Life Issues Fig. SE1-15-04ab 6892-01 C M Y K network of blood vessels food in the process of digestion A. muscle tissue villi B. Cross-Section of the Small Intestine Nutrients are absorbed by the blood across the wall of the small intestine. Finger-like projections from the wall of the small intestine are specialized structures known as villi (singular, villus). Nutrients must pass through villi and the walls of tiny blood vessels to enter the circulatory system.
ACTIVITY 4 DIGESTION: AN ABSORBING TALE 20 BODY made of? It contains bacteria, substances that your body can’t digest, and some remaining water. Bacteria live and grow in your intestines, and they help you in several ways. They break down some plant material that your body can’t break down on its own, they make vitamin K, and they help prevent harmful bacteria from finding a home. The trade-off for providing a home for these helpful bacteria is the gas and odors they can produce. STOP TO THINK 4 Which body systems work together to remove waste from your body? ANALYSIS 1. What are some of the functions of the digestive system?83 2. Imagine taking a bite of a burrito. Follow the beans in the burrito through the organs in the digestive system. Draw a model of the digestive system. Label any parts of the digestive system that help digest the food or help the body get nutrients from the food. Explain what happens at each step of the way.84858687 88 89 90 3. Take a closer look at the villi of the small intestine (Part B in the diagram of the cross-section of the small intestine). How do the villi help nutrients move into the blood quickly?91 Hint: What would happen if there were no villi but only a smooth surface? 4. Body systems constantly interact with each other. Give examples of two other body systems that interact with the digestive system, and explain the function of these interactions.92 9394 95 96 EXTENSION To find out more about the human body and its systems, visit the SEPUP Third Edition Body Systems page of the SEPUP website at www.sepuplhs.org/middle/third-edition, and go to the suggested resources for this activity. 83 NGLS1A3 84 NGLS1A3 85 SELTWR1 86 NGCCSM1 87 SEASEX1 88 NGSPCE6 89 SEASMD1 90 NGSPEA2 91 NGLS1A3 92 NGLS1A3 93 NGCCSM1 94 NGSPCE6 95 SEASEX1 96 NGSPCE1
BODY 21 5 Food Breakdown m o d e l i n g All organisms need both matter and energy to grow and reproduce. They get both from food. Scientists use the word matter to describe physical substances, such as the sugars in food, as well as other molecules, like water, carbon dioxide, and oxygen. Matter cannot be created or destroyed; rather, it cycles through organisms and the environment in different forms. Energy is the ability to cause an object to change, move, or do work. Like matter, energy cannot be created or destroyed. Organisms need energy to move and to build and repair structures within their bodies using the matter they get from food.9798 To access the energy and matter in food, you must first break down your food (i.e., digest it) into smaller pieces that can be absorbed and then enter your cells. In this activity, you will model how your cells get both energy and matter from food. First, you will learn about the kinds of matter in food. You will then learn how your body breaks down the food to get the matter and energy it needs to function properly and keep you healthy.99 GUIDING QUESTION How does food provide energy and matter for organisms? 97 NGCCEM1 98 NGCCEM1, NGCCEM3 99 NGSPDM2
ACTIVITY 5 FOOD BREAKDOWN 22 BODY MATERIALS For each group of four students 1 set of 12 colored oval pop beads (red, blue, green, and white, 3 of each) 1 set of yellow round pop beads For each pair of students 1 set of colored pencils 1 Student Sheet 4.1, “Digestive System Outline” PROCEDURE Read each section of text below, and follow the steps for developing a model. Your model will show the substances in food and how they are used as a source of matter and energy for cells.100 Part A: Composition of Matter in Food The foods you eat are mostly made up of different types of matter called fats, proteins, and carbohydrates. Fats, proteins, and carbohydrates are all made of very large molecules that are chains of smaller molecules that contain carbon. For your body to access the energy stored in these large molecules, they must be broken down into smaller molecules. Once the large molecules are broken down, your body can use the energy that is stored in the food. The large molecules and the smaller molecules (known as subunits) are shown in the following table. Composition of Substances in Food LARGE MOLECULE SMALLER MOLECULE (SUBUNIT) carbohydrate sugar protein amino acid fat fatty acid As the table shows, carbohydrates are chains of subunits called sugars. Proteins are chains of subunits called amino acids. Fats are chains of subunits called fatty acids. In this activity, you will focus on what happens to the carbohydrates and proteins in a hamburger after you eat it. 100 NGLS1C2
FOOD BREAKDOWN ACTIVITY 5 BODY 23 1. Working in your group of four, one pair will make a protein model, and one pair will make a carbohydrate model. a. To make a protein, connect 12 oval pop beads. You can connect the amino acid subunits in any order you’d like. b. To make a carbohydrate, connect 10 yellow round pop beads. You can connect the sugar subunits in any order you’d like. 2. In your science notebook, draw a colored diagram of the protein and the carbohydrate your group made. These represent the proteins and carbohydrates in a hamburger. Part B: Modeling Food Breakdown101 102 All organisms get the matter and energy they need by breaking down substances in food. Your organs, tissues, and cells work together to provide your body with the energy and materials it needs to grow. In many organisms, the digestive system is responsible for the process of digestion—breaking down food for energy and matter. The first stage of digestion is to break large molecules like carbohydrates and proteins into their smaller subunits. In humans, this process begins in the mouth, where food is mechanically broken into smaller pieces. Chemical reactions that break down food also begin in the mouth and continue as food passes through the organs of the digestive system. The stomach and small intestine are the most important organs for the chemical breakdown of food. The carbohydrates in your food are broken down into sugars, and the proteins are broken down into amino acids. These subunits of matter can now enter your cells. In the cells, some of the subunits are broken down further to release energy for your cells to use. 101 NGPEL17, NGSPDM2, ELRS689 102 NGLS1A1
ACTIVITY 5 FOOD BREAKDOWN 24 BODY 3. Model what happens in the digestive system to the carbohydrate and protein chains you made in Step 1. 4. Use a clean copy of Student Sheet 4.1, “Digestive System Outline,” to draw a diagram of what happens to the bun (the carbohydrate) and hamburger (the protein) as it moves from the mouth to the stomach and small intestine.103 ANALYSIS 1. Why do living organisms need the following: a. Food? b. Energy? c. Matter? 2. Describe what happens to matter, such as a protein or a carbohydrate, after it is eaten. Be sure to include the structures where each step occurs and the function of each structure. 104105 106 3. Based on what you learned in “Digestion: An Absorbing Tale” and this activity, draw a diagram (or create another type of model) to show what happens to the food you eat. Your model should show the movement of matter and the release of energy stored in food. 107108 109 110 4. Revisit the issue: Many medications are taken orally: You swallow them, and they go into your digestive system. Why would it be important for a doctor to understand the digestive system and how it interacts with other body systems? 103 ELRS682 104 ELRS682 105 NGLS1C2 106 NGSPCE1 107 NGSPCE1, SEASMD1, NGLS1A1 108 NGPEL17, NGCCEM3, NGSPDM2 109 SEASMD1 110 NGCCEM2
BODY 25 6 Observing Organisms l a b o r at o r y Humans are not the only organisms with body systems. Many other animals have systems with the same functions as those in humans, though sometimes with different structures. For example, an octopus has three hearts in its circulatory system. Two of the hearts pump blood to its gills. Scientists will often study other organisms to learn more about human body systems. In this activity, you will investigate the response of an organism—in this case, a blackworm known as Lumbriculus variegatus—to stimuli. Stimuli (singular stimulus) are inputs from the environment, such as a sound or a touch. You will make observations of what you see. You can then make inferences—ideas based on your observations— about what is happening. 111 GUIDING QUESTION What can your observations tell you about how an organism’s nervous system will respond to stimuli? MATERIALS For each pair of students 1 Lumbriculus variegatus, or similar test organism 1 100-mm petri dish 1 piece of filter paper 1 pipet 1 small paintbrush spring water (or treated tap water) unbleached paper towels 111 NGLS1D1 An octopus has a circulatory system that pumps blood, just like a human’s. However, the octopus has three hearts instead of just one.
ACTIVITY 6 OBSERVING ORGANISMS 26 BODY PROCEDURE112 113 1. Discuss with your group some guidelines for studying animals in the classroom. Record your ideas in your science notebook. Be prepared to share these ideas with the class. 2. Draw a table in your science notebook like the one that follows, and record your observations and inferences about the blackworm. Not every observation will result in an inference. Blackworm Observations Inferences 3. Pour 1–2 centimeters (cm) of water into the bottom of the petri dish. 4. Use the pipet to add a single blackworm from the culture to your petri dish. (Do not pick a blackworm that is dark and has a lighter section at one or both ends; this worm has recently been broken and is regenerating itself.) 5. Carefully observe the blackworm. Then use the brush to gently investigate this organism. 6. How much can you find out about a blackworm? Without injuring the worm, explore its behavior. Use the following questions to help you explore, and record your observations: • How does it move? • Does it respond differently to different actions on various parts of its body, such as touching? • Can you identify which end is the head? • What else do you observe? 7. Place the filter paper in the lid of the petri dish. Use the pipet and a few drops of water to completely moisten the filter paper. 8. Use the pipet to move the blackworm onto the filter paper. 112 NGLS1D1 113 NGSPPI3
OBSERVING ORGANISMS ACTIVITY 6 BODY 27 9. Observe the blackworm’s movement on this surface. How does its movement here compare with its movement in water? Record your observations. 114 10. Return your blackworm to the class culture before cleaning up. EXTENSION Place a blackworm on a microscope slide. Add 1 drop of water. (If there is too much water on the slide, use a pipet to suction off the excess water.) Observe the worm under low and medium power. What internal structures can you see? What do you think is the function of these structures? ANALYSIS 1. Based on your observations, predict how a blackworm would respond if it were gently touched with a toothpick on the following spots on its body: • Right side • Left side • Front (“head”) of body • End (“tail”) of body 115 116 2. Many organisms, including blackworms and humans, respond to external stimuli. Describe how the blackworm’s behavior changed in response to the stimulus of the brush. 117 3. Imagine that you are sitting in a very quiet room when suddenly there’s a very loud bang behind you, like a firecracker exploding. a. Predict how you would behave in response to the stimulus of the loud noise. b. What body systems would be involved in your response? c. What would each of these body systems do? 4. Based on your blackworm observations, answer the following questions: a. What body systems of the blackworm did you investigate? b. How are these systems similar to or different from human systems? c. What do you think scientists might learn about the human nervous system by studying an organism like the blackworm? 114 NGSPP13 115 NGCCCE1 116 NGLS1D1 117 NGLS1D1
BODY 29 7 Can You Feel the Difference? l a b o r at o r y Scientists are interested in how people and other organisms respond to the environment. Many organisms have very similar body systems that interact when the organism responds to stimuli. For example, people, horses, cats, mice, fish, spiders, and even blackworms all have some kind of nervous system. In some organisms, such as people, horses, cats, and mice, the systems are more sophisticated and can take in more types of information. For example, a person can clearly see a car coming toward them on a street (the color, how fast it’s going, how big it is)—but a blackworm can only detect the shadow and movement of a fish approaching it in a stream; it cannot clearly see the fish. People are able to use their senses—touch, sight, hearing, smell, and taste—to get complex information about their surroundings. This information travels through nerves to the human brain. In this activity, you will investigate one of your own senses: your sense of touch. You will examine how your nervous system gathers and puts together information from stimuli in the environment around you. You will also look at how that information is interpreted by your brain. 118119 GUIDING QUESTION How does your brain gather and synthesize information from sensory receptors in your skin? MATERIALS For each pair of students 1 2-point sensor 6 plastic toothpicks For each student 1 Student Sheet 7.1, “Touch-Test Data” 1 Student Sheet 7.2, “Sensitivity to Two Points: Class Results” 118 NGLS1D1 119 NGPEL18
ACTIVITY 7 CAN YOU FEEL THE DIFFERENCE? 30 BODY SAFETY Be careful when doing the touch tests. Press gently when testing, making sure to only slightly depress the skin surface. PROCEDURE Part A: Comparing Sensitivity on Parts of Your Arm120 121 1. Slide two plastic toothpicks into the 2-point sensor on the side marked “1.5 cm.” 2. With your eyes open, investigate your sense of touch by touching the skin of your fingers, the palm of your hand, and your forearm with the point of just one toothpick. 3. With your eyes open, touch your fingers, palm, and forearm with the points of both toothpicks. Notice what the points look like as they touch your skin, and compare that to how it feels. 4. Record your observations in your science notebook while your partner investigates their own sense of touch. 5. Write your partner’s and your names in the first column of the table in Part A of Student Sheet 7.1, “Touch-Test Data.” Decide who will be Partner 1 and who will be Partner 2. Partner 1 closes their eyes while Partner 2 touches the skin on Partner 1’s fingers with either one or two toothpick points. Partner 2 should touch just hard enough to see that the points are barely pushing down on the skin. Randomly alternate between one and two points. Can Partner 1 tell the difference? 120 NGSPPI4 121 NGLSID1, NGSPPI2
CAN YOU FEEL THE DIFFERENCE? ACTIVITY 7 BODY 31 6. In the table, Partner 2 records their observations about Partner 1’s ability to tell the difference between one and two points on their fingers. 7. Partner 2 now repeats Steps 5 and 6 on Partner 1’s palm and forearm. 8. Switch places and repeat Steps 5–7. 9. Discuss with your partner what you observe when you are lightly touching your partner’s skin with one or two toothpick points. What does the skin look like when you lightly touch it with the sensor? How far is the skin depressed?
ACTIVITY 7 CAN YOU FEEL THE DIFFERENCE? 32 BODY 10. A variable is the part of an experiment that can change. For example, one variable in this experiment is the number of points on the sensor. Discuss with your partner the variables that were easy to control and the variables that were harder to control. List these in your science notebook. Discuss how you will control the more difficult variables in Part B of the activity. Part B: Investigating the Sensitivity of Your Palm 11. What is the smallest distance apart—0.7 cm, 1.5 cm, or 2.0 cm—at which you think you can still feel two points on the palm of your hand? In your science notebook, record your hypothesis. Explain why you made this prediction. 12. Identify your dominant hand. (This is usually the hand you write with.) Throughout the experiment, you will test your dominant hand. 13. Begin completing Part B of Student Sheet 7.1, “Touch-Test Data.” Write your name, and circle which of your hands is dominant. You will begin by testing the palm of your hand, so circle “palm” as the part tested. 14. Since you will test your partner (and vice versa), switch Student Sheets so you can record the data on their sheet. 15. Slide two toothpicks into each side of the 2-point sensor as shown at the right. You should end up with toothpicks on three sides, with the toothpick points 0.7 cm apart, 1.5 cm apart, and 2.0 cm apart. 16. Practice using the 2-point sensor so that you can safely and easily test your partner with one or two points, using any of the three sides. 17. Again, decide who will be Partner 1 and who will be Partner 2. Before starting the touch tests, Partner 1 should close their eyes. Remember, neither of you should try to guess the right answer. The goal is to report what you actually feel: one point or two. 18. Partner 2 can choose which test to do first: 0.7 cm, 1.5 cm, or 2.0 cm. You can start with any test you want, but be sure you complete all the tests in each row. Don’t tell your partner which test you are doing.
CAN YOU FEEL THE DIFFERENCE? ACTIVITY 7 BODY 33 19. For each test, remember to touch just hard enough to see that the points are barely pushing down on the skin. a. For the first 0.7-cm test, turn the 2-point sensor to the 0.7-cm side, and touch your partner’s palm with just one point. b. For the first 1.5-cm test, turn the sensor to the 1.5-cm side, and touch your partner’s palm with just one point. c. For the first 2.0-cm test, turn the sensor to the 2.0-cm side, and touch your partner’s palm with two points. 20. For each test, have your partner report whether they feel one or two points. Circle “Yes” on the Student Sheet if your partner’s response was accurate, and “No” if it was not. 21. After all the touch tests in the table are completed for Partner 1, switch roles and have Partner 1 do the testing on Partner 2 by repeating Steps 17–20. 22. Once all tests are completed each partner should take back their original Student Sheet. 23. Complete the rest of Student Sheet 7.1. 24. If you have time, repeat this experiment to test the sensitivity of your and your partner’s fingertips and forearms. 25. Follow your teacher’s instructions to report your data, and record the class data on Student Sheet 7.2, “Sensitivity to Two Points: Class Results.” ANALYSIS 1. Review the data you collected during this activity. 122 123 a. According to your data, what can you conclude about your sensitivity to two-point touches? How does this conclusion compare with your hypothesis? b. Compare your results with your partner’s. How similar or different are your results? c. Compare your results with those of another pair of students. How similar or different are your results? 2. Look at the class results on Student Sheet 7.2. Compare the smallest distance at which you could feel two points with the results of the rest of the class. What can you conclude about the sensitivity of different people to touch? Is it possible to make conclusions about people in general? 122 SEASAD1 123 NGSPAD3
ACTIVITY 7 CAN YOU FEEL THE DIFFERENCE? 34 BODY 3. You were able to determine the smallest distance at which you could still feel two points, using only the two-point touch data. The one-point touches acted as a control—the data collected were used to compare with your experimental data. Why would you need a control when experimenting on people? 4. How does your body normally gather information for your brain to process? How is that different from this experiment? 5. Revisit the issue: Imagine that you accidentally touched a hot stove. Explain how you would react in the short term and the long term, and describe what body systems would be involved in your behavioral response. 124125126 127 6. Do you have sufficient information from this activity about your response to the touch tests to conclude that the touch tests sent signals to your brain? Explain. EXTENSION 1 Ask your teacher to post your class data on the SEPUP Third Edition Body Systems page of the SEPUP website at www.sepuplhs.org/ middle/third-edition. Your teacher will show you the data posted by other students. What can you conclude about the sensitivity of different people to touch? Explain your ideas. EXTENSION 2 Design and conduct an experiment to test additional distances between the two points to determine to the nearest 0.1 cm people’s sensitivity to two-point touches. Ask your teacher to post your class data on the SEPUP Third Edition Body Systems page of the SEPUP website at www.sepuplhs.org/middle/third-edition. You can compare your class data to the data posted by other students. 124 SEASEX1 125 NGCCCE1 126 NGPEL17 127 NGSPOE2
BODY 35 8 Finding the Nerve r e a d i n g I n the “Can You Feel the Difference?” activity, you probably found that some parts of your arm were more sensitive than others. In this Reading, you will learn about some reasons for these differences and about how your body takes in and processes information in different ways. You will also learn more about how the nervous system interacts with other systems, such as the digestive system and muscular system. The interactions of these systems allow us to function but also mean that diseases like pellagra often affect more than one system in the body. GUIDING QUESTION How does your body gather and synthesize information to respond to stimuli? PROCEDURE 1. Read the text below. 2. Follow your teacher’s instructions for how to use the Stop to Think questions.128 READING Gathering Information129130 You use your senses to gather information about your environment. Your senses include sight, hearing, taste, smell, and touch. To understand how you feel the objects you touch, you need to know a little about your nervous system. Your nervous system includes your brain, spinal cord, and nerves. The diagram (right) shows how these parts of your nervous system are connected. Nerves are made up of bundles of nerve cells, or neurons, and are found throughout your body. 128 SELTST1 129 NGLS1D1 130 NGCCSM1 Human Nervous System
ACTIVITY 8 FINDING THE NERVE 36 BODY The human body contains over 100 billion neurons, which take in information from the world. The nerve cells that sense this information are called sensory neurons. Sense receptors are located at the end of your sensory neurons. On your tongue and in your nose, you have receptors that detect chemical inputs, which allow you to taste and smell. Sensory receptors in your eyes detect light waves, allowing you to see, and sensory receptors in your ears detect sound waves, allowing you to hear. In other parts of your body, you have sensory receptors that detect mechanical inputs. For example, these sensory receptors have helped you collect information about the weight of your backpack when you pick it up and think, “It’s heavy!”131 STOP TO THINK 1 a. Why are the nerves that take information from our world called sensory neurons? b. What kinds of information do sensory neurons detect? Transmitting Information Information travels from sensory neurons all over your body along nerves to your spinal cord before continuing to your brain. The sensory neurons that connect to the nerve cells in your spinal cord are called interneurons. Interneurons are also found in your brain. The interneurons in your brain connect to millions of interconnected sensory neurons. They analyze all the information from the interneurons and help you understand what your sensory neurons have detected. For example, the interneurons help you identify the object at your feet as a dog. As a result, your brain can then provide directions to other nerve cells called motor neurons. Motor neurons send signals to your muscles that cause you to move in response to a stimulus. For example, they might signal your muscles to reach down and pet the dog. Sometimes there is a need for a reflex action, such as when you touch a hot stove. In this case, you react before the message gets to your brain. The interneurons in your spinal cord directly signal the motor neurons 131 SELTST1 Signals travel from nerves in your body to your brain. These signals can travel up to several hundred miles per hour!
FINDING THE NERVE ACTIVITY 8 BODY 37 of your arm and hand to move your hand away fast. When the original message does get to your brain, it helps to form a memory of what has happened so that you know not to touch a hot stove next time.132 STOP TO THINK 2 a. Someone accidentally bumps into you in the hallway. What part of your body detects the feeling of being bumped? b. Where in your body is this feeling analyzed? c. “Inter” means between. Why are the neurons in the spinal cord and brain called interneurons? 133 Processing Information Sometimes your nervous system responds to messages that you provide, and sometimes your nervous system responds to messages from your brain that you are not aware of. For example, imagine that you decide to eat a sandwich. Your brain sends signals along nerves to direct your muscles to pick up the sandwich and take a bite. But what happens after you swallow? You do not have to think about directing your body to process the food. Your body automatically moves food through your digestive system and processes it. For this to happen, muscles inside your body must move—for example, the muscles in your stomach. These muscles are controlled by the automatic, or involuntary, part of your nervous system. You don’t even have to think about it! STOP TO THINK 3 a. Is breathing completely involuntary? Explain. b. Which body systems interact with the involuntary part of your nervous system? Can you think of two examples when these interactions might occur? 132 SELTST1 133 ELRS684 3030 LabAids SEPUP SALI SB Figure: SALI SB A 06.04 LegacySansMedium 10/11.5 interneuron sensory neuron motor neuron muscle Path of a Nerve Impulse
ACTIVITY 8 FINDING THE NERVE 38 BODY Even when you are not consciously thinking about what your body is doing, your brain is controlling your body’s movements. Your brain weighs only 3 pounds and is made up mainly of water and fat, and yet it: • Processes information from the world around you through your senses • Controls and coordinates all of your movements • Controls basic life processes, such as digestive processes, body temperature, blood pressure, heart rate, and breathing • Stores sensory inputs for a long time as memories • Allows you to think, reason, dream, and experience emotions The parts of your brain have various functions. The largest and wrinkled part of the brain that you see is called the cerebrum. The folds or wrinkles increase the surface area of the brain, allowing more room for neurons and making it more efficient. This is where all the thinking and reasoning you do takes place. Specific parts of the cerebrum control certain types of thought processes and actions. The two smaller parts of the brain are the cerebellum and the brain stem. The cerebellum controls the coordination of movement, posture, and balance. During complex voluntary movements (such as those involved in learning to ride a bike), many parts of your brain work together to perform 3030 LabAids SEPUP SALI SB Figure: SALI SB A 06.05 LegacySansMedium 10/11.5 motor control taste touch and pressure vision hearing smell speech Functions of the Cerebrum 3030 LabAids SEPUP SALI SB Figure: SALI SB A 06.06 LegacySansMedium 10/11.5 cerebrum cerebellum brain stem Structure of the Human Brain
FINDING THE NERVE ACTIVITY 8 BODY 39 the sequence of movements necessary to successfully complete the desired action. The more you practice a movement (like riding your bike), the more your brain remembers how to smoothly perform this sequence of movements. Memories are stored in different parts of the brain, depending on what they relate to. Deep within the brain is the brain stem. This is where the basic life functions, such as heartbeat, blood pressure, and breathing, are controlled.134 STOP TO THINK 4 a. When you decide what to wear in the morning, which of the three parts of your brain do you use? Explain. b. What is a benefit of the cerebrum having folds and wrinkles? c. What part of the brain enables you to breathe, even when you are asleep? Differences in Sensitivity Now you know how you sense information from the outside world and react to it. You may have noticed that some parts of your body are more sensitive than others. If you are touched with two closely spaced points, some parts of your body will be able to detect that there are two points, whereas other parts of your body will only be able to detect one point. When something touches your arm, you feel it only if it is detected by the nerve endings (or sensory receptors) in your skin. You have sensory nerves in your body that detect pressure, heat, sounds, smells, and light. The nerve endings that detect pressure on your skin are called touch receptors. They help carry a message from your skin to your brain. Some parts of your body have more touch receptors than others. When two points stimulate the same touch receptors, you feel the points as one touch. When they stimulate different touch receptors, you feel two different touches. The illustration shows the concentration of touch receptors on a hand. Notice that the tip of the finger has more touch receptors than the rest of the finger. When you reach out to touch something, you often use your fingertips. Some people with limited or no vision can read Braille. Braille is a written language that uses raised dots instead of letters. Braille is read with fingertips. 135 134 SELTST1 135 SELTST1 The illustration shows touch receptors on a human hand. The blue shading shows the concentration of the touch receptors. The darker the blue, the more touch receptors there are.
ACTIVITY 8 FINDING THE NERVE 40 BODY There are sensory receptors in your body that also respond to pain. For example, if you fall and bruise your knee, you have damaged the cells. Those cells release a chemical that activates the receptors that sense pain. The pain receptors send the message to your brain for a response. If you take a pain reliever, like ibuprofen, it prevents the damaged cells from releasing the chemical, so your brain either does not get the pain message or the pain message is not very clear. ANALYSIS 1. Look at and think about your hand. a. Where would you expect to have more touch receptors: on the palm of your hand or on the back of your hand? Explain your ideas. b. Explain how you could test your answer. 2. When your partner touched you with the toothpick points in the “Can You Feel the Difference?” activity, how did you sense it? Describe or draw the path through the nervous system that enabled you to identify if it was a one- or two-point touch. 3. Review your results from the activity “Can You Feel the Difference?” Based on what you now know, where on your arm—fingers, palm, or forearm—do you have the fewest touch receptors?136 137 4. Revisit the issue: Imagine that you just dipped your foot into a swimming pool. You expected the pool to be warm, but it was ice cold! Which of your body systems help you gather and synthesize information to react to this situation? Explain the cause-and-effect sequence that leads to your reaction. 138 139 140 141 142 136 NGSBOE2 137 NGSPOE2 138 SEASEX1 139 NGLS1D1 140 NGCCSM1 141 NGPEL18 142 NGCCCE1