Idea Transcript
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iScience Grade 7, Davis County Edition
Chapter Chapter12
Interactions of Human Body Systems How do human body systems interact and support life?
What is going on here? In this photo, the small vessels shown in red are part of the circulatory system. The vessels surround structures in the lungs called alveoli (al VEE uh li), shown in blue.
• Why do you think these vessels surround the alveoli? • What do you think would happen if the vessels were not there? • How do human body systems interact and support life?
Chapter 12/Interactions of Human Body Systems
Get Ready to Read What do you think? Before you read, decide if you agree or disagree with each of these statements. As you read this chapter, see if you change your mind about any of the statements. 1 Elements can be broken down into smaller parts. 2 Organic compounds are foods grown without pesticides. 3 Organ systems work together. 4 Nutrients are processed by the skeletal system. 5 The nervous system moves oxygen through the body. 6 You do not control reflexes.
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Concepts in Motion
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Multilingual eGlossary
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Lesson 1 Reading Guide Key Concepts ESSENTIAL QUESTIONS
• What are the functions of
inorganic substances in the human body?
The Human Body
• What are the functions of
organic substances in the human body?
• How does the body’s
organization enable it to function?
Vocabulary macromolecule monosaccharide amino acid nucleotide
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Multilingual eGlossary
Strange Clothing? Have you ever seen a multicolor scan of a human body? This is a thermal scan that shows the temperature in different areas of the body. Red, or “hot,” areas might indicate additional blood flow that could affect body function.
Chapter 12/Interactions of Human Body Systems
Launch Lab
10 minutes
Will it disappear? Over 60 percent of your body’s weight is due to water. Water in our cells and body fluids serves an important role in the movement of materials throughout our bodies. 1 Read and complete a lab safety form. 2 Half fill a beaker with water. 3 Add a spoonful of sugar, and stir for 15 seconds. 4 Observe what occurs in the beaker.
Record your observations in your Science Journal. 5 Empty the beaker’s contents and clean the beaker according to your teacher’s instructions. 6 Repeat steps 2–5 replacing the sugar with salt, corn syrup, baking soda, an antacid tablet, a multivitamin, and candy bits.
Think About This 1. What happened to each of the substances when they were stirred into the water? 2.
Key Concept Why do you think water makes up such a large portion of your body?
Life and Chemistry Have you ever modeled a volcanic eruption by mixing vinegar and baking soda? When baking soda—also called sodium bicarbonate ∙NaHCO3∙—combines with the acetic acid ∙CH3COOH∙ in vinegar, a chemical reaction occurs. You might recall that a chemical reaction is the process that occurs when compounds, called reactants, form one or more new substances, called products. During a chemical reaction, bonds are broken and new bonds are formed. When acetic acid and sodium bicarbonate react, water ∙H2O∙, carbon dioxide ∙CO2∙, and sodium acetate ∙NaCH3COO∙ form. Bubbles form when vinegar and baking soda mix, as shown in Figure 1. The bubbles are caused by the CO2 gas and the water that are released as products of this chemical reaction. Chemical reactions are everywhere. Moldy bread and green pennies are the result of chemical reactions. As you will read in this lesson, chemical reactions also occur in your body. These chemical reactions take place in your body’s cells. They are essential for human life.
Figure 1 When baking soda and acetic acid combine, water, CO2 gas, and sodium acetate form.
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Iron
Carbon
Sodium
Sulfur
Calcium
Phosphorus
Figure 2 Elements have different textures, colors, and properties.
Elements and Compounds Recall that elements are the basic units that make up chemicals. Elements are substances that cannot be broken down or transformed into another element during a chemical reaction. Elements have different physical properties, as shown in Figure 2. Although there are almost 100 elements found in nature, six elements—carbon, oxygen, hydrogen, nitrogen, calcium, and phosphorus—make up 99 percent of your body’s mass.
Reading Check Which elements make up most of the
body’s mass?
Use two sheets of paper to make a layered book. Label it as shown. Use it to record your notes on human body chemistry.
Essential to Life Water Ionic Compounds Organic Substances
Compounds are substances made of two or more elements. Unlike elements, compounds can be broken down into simpler substances. The acetic acid and sodium bicarbonate you read about at the beginning of this lesson are compounds. Acetic acid is formed when the elements carbon, hydrogen, and oxygen combine. Compounds can be made by binding elements together in two different ways—ionic or covalent bonds. Ionic bonds are formed when electrons travel from one element to another. One element has a positive charge, and the other has a negative charge. The opposite charges attract. Table salt, or sodium chloride (NaCl), is an example of a compound that has an ionic bond. Covalent bonds are formed when the electrons in each element are shared. Many gases in the atmosphere, such as oxygen ∙O2∙ and nitrogen ∙N2∙, form by covalent bonds.
Chapter 12/Interactions of Human Body Systems
Inorganic Substances Inorganic compounds are everywhere on Earth. Inorganic compounds are substances that do not contain carbon-hydrogen bonds. Substances such as ammonia ∙NH3∙ and NaCl are inorganic compounds. Many inorganic compounds are essential for human life. Water and oxygen gas are inorganic compounds that humans need to survive.
Ionic Compounds As you read earlier, NaCl is an inorganic compound that forms by ionic bonding. Recall that ionic bonds are formed when a positive ion is attracted to a negative ion. When a substance gives up or gains an electron, it is called an ion. In the compound NaCl, Na+ is a positively charged ion, and Cl− is a negatively charged ion. Many ions are important for survival. For example, calcium ∙Ca2+∙ helps nerve and muscle cells function and makes up bone. These compounds rely on water to move through the body. Reading Check Explain what an ion is. Water You might know that water is called the universal solvent. What does that mean? A solvent is a substance that dissolves other substances. Ionic compounds dissolve well in water and allow ions such as Na+, Cl−, and Ca2+ to travel through the body dissolved in water. Water is able to dissolve many substances because of its polarity. Water molecules are formed by covalent bonds that link the hydrogen (H) to the oxygen (O). As shown in Figure 3, water is able to easily dissolve ionic substances because the positive ions in the compound are attracted to the oxygen end of the molecules and the negative ions are attracted to the hydrogen end of the molecules.
Key Concept Check How does water
help the body obtain ionic substances?
The Structure of a Water Molecule Salt dissolved in water + + -
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Review
Personal Tutor
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- + + - + + + + - + + + + + + + + + + + + +
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+ + Water molecule
Figure 3 A water molecule has a bent shape with the large oxygen atom at one end of the molecule. This bent shape results in the oxygen end of the molecule having a negative charge and the hydrogen end having a positive charge. H+ ions are shown in blue, O– in red, Na+ in grey, and Cl– in green.
Visual Check Which ion is attracted to the oxygen end of the water molecule?
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Organic Substances
WORD ORIGIN macromolecule from Greek makro-, means “long”; and Latin molecula, means “mass”
Macromolecules Figure 4 Much like a train contains many boxcars linked together, macromolecules are many organic compounds joined together.
Visual Check Which macromolecule is made of nucleotide polymers?
You might have heard the word organic used to describe certain fruits and vegetables. However, when used in science, the term organic describes compounds that contain carbon and other elements, such as hydrogen, oxygen, phosphorus, nitrogen, or sulfur, held together by covalent bonds. Organic compounds carry out many different functions. Substances that form from joining many small molecules together are called macromolecules. The four macromolecules in the body are carbohydrates, lipids, proteins, and nucleic acids, shown in Figure 4.
Carbohydrates Sugars, starches, and cellulose are carbohydrates. Carbohydrates are formed when simple sugars, called monosaccharides (mah nuh SA kuh ridez), are joined together. Carbohydrates are the body’s major source of energy.
Carbohydrate During digestion, humans break down carbohydrates into glucose, a monosaccharide, and store it as glycogen.
Lipid Lipids, also called fats, contain fewer oxygen atoms than carbohydrates and do not dissolve in water.
Lipids Triglycerides and cholesterol are lipids (LIH pihdz), and, like carbohydrates, they are made from carbon, hydrogen, and oxygen. Lipids help insulate your body and are a major part of cell membranes. Proteins The adult human body is made up of 10–20 percent protein. Proteins form when amino (uh MEE noh) acids, the building blocks of protein, join together. Some proteins give cells structure, some help cells communicate, and some are enzymes.
Nucleic Acids Much as computer chips store
Protein All amino acids consist of carbon, oxygen, hydrogen, and nitrogen. Some also contain sulfur.
Nucleic acid DNA is made of two strands of nucleotide polymers. RNA is made of a single strand.
information, nucleic acids are macromolecules that store information used by the body to perform different functions. Nucleic acids are formed when nucleotides (NEW klee uh tidez), molecules made of a nitrogen base, a sugar, and a phosphate group, join together. The body contains two types of nucleic acids, DNA and RNA.
Key Concept Check What are the
functions of organic compounds in the human body?
Chapter 12/Interactions of Human Body Systems
The Body’s Organization In order to function and survive, macromolecules in the human body must be organized in different compartments. For example, most of the DNA is stored in the nuclei of cells. Cholesterol and other types of lipids are used to form cell membranes. Organizing macromolecules in specific locations helps cells carry out specific functions.
Bone cell
Bone tissue
Recall that cells are the building blocks of all living things. Cells have different shapes depending on their function. Neurons are long and slender so they can carry information over long distances. Red blood cells are flexible disks and can move easily through blood vessels.
Bone (organ)
Tissues are made of a group of cells that work together and perform a function. Cardiac muscle cells form a tissue that helps the heart pump blood throughout the body. An organ is a group of tissues that work together and perform a function. The liver, spleen, and lungs are all organs.
Skeletal system
An organ system, such as the one in Figure 5, is a group of organs that works together and performs a specific task. Organ systems work together and help the body communicate, defend itself, process energy, transport substances, and move.
The human Figure 5 body is made of cells, tissues, organs, and organ systems that work together.
Key Concept Check How does the body’s organization enable it to function?
MiniLab
20 minutes
Does teamwork stack up? For your body to function properly, your body systems must work together. How can your team work together to complete a task? By doing this lab, you will understand how important teamwork is for your body functions. 1 Read and complete a lab safety form. 2 Obtain a piece of string for each group
member, three plastic cups, and a rubber band.
3 Using only the materials provided, stack
the cups in a pyramid. Do not touch the cups with any part of your body.
Analyze and Conclude 1. Explain What method did you use to form the pyramid? 2. Evaluate How did your team work together to form the pyramid?
3.
Key Concept Compare how your team worked together to how systems work together in the body.
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Lesson 1 Review Visual Summary
Assessment
Online Quiz
Use Vocabulary Elements are substances that cannot be broken down or transformed into other elements during chemical reactions.
1 Distinguish between nucleotides and amino acids. 2 Use the term monosaccharides in a sentence. 3 Define macromolecule in your own words.
Understand Key Concepts 4 Which is a lipid?
+ + -
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- + + - + + + + - + + + + + + + + + + + + +
+
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Water dissolves ionic substances easily.
A. B. C. D.
cellulose cholesterol DNA starch
5 Distinguish between proteins and nucleic acids. Organ systems are groups of organs that work together and perform a specific task.
6 Draw a picture that illustrates how water dissolves NaCl.
Interpret Graphics 7 Summarize Copy and fill in the graphic organizer below to show how the human body is organized.
Cells Use your lesson Foldable to review the lesson. Save your Foldable for the project at the end of the chapter.
8 Describe the differences in the structures of the macromolecules shown below.
What do you think You first read the statements below at the beginning of the chapter.
1. Elements can be broken down into smaller parts.
Critical Thinking
2. Organic compounds are foods grown
9 Hypothesize how the body would function if cells were not organized into tissues.
3. Organ systems work together.
10 Relate the four macromolecules to their functions in a cell.
without pesticides.
Did you change your mind about whether you agree or disagree with the statements? Rewrite any false statements to make them true.
Chapter 12/Interactions of Human Body Systems
Your Remarkable, Renewable Skin Keeping You Safe from Head to Toe
L
ots of organs keep your body working, but only one covers you from head to toe— your skin. In many ways, your skin is like body armor. It protects you from bacteria and other germs, absorbs impacts, and blocks ultraviolet (UV) light from the Sun. Luckily, when there’s a crack in this armor, such as a cut or a burn, your skin can repair itself, or regenerate. To do this, it works closely with the circulatory system. When a wound bleeds, platelets in your blood rush to the injury. They clump together, forming a blood clot and stopping the bleeding. Then the clot dries into a hard scab that protects the area. Underneath the scab, red blood cells deliver nutrients and oxygen to help new skin cells form. As the skin regenerates, the wound closes. This process works well for most skin injuries. But sometimes a wound is too large, and the skin can’t heal on its own. When this happens, doctors can treat the area with a skin graft. In this process, the injured skin is replaced with healthy skin taken from another part of the injured person’s body. However, a skin graft depends on the circulatory system to succeed. For the new skin to stay healthy, it needs nutrients and oxygen that are carried by blood. What happens if an injured person doesn’t have enough healthy skin to use as a skin graft? Skin injuries can sometimes heal using artificial skin. To make artificial skin, scientists begin with a mesh of connective tissue called collagen. Skin cells are grown on the collagen to form sheets of skin tissue. Placing the artificial skin over large wounds encourages new skin to grow and protects the wounds from infection.
Healed skin graft
Skin graft site Skin graft
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artificial skin search how re to r ne rt a pa findings with H Work with ounds heal. Share your R E S E A RC w to help large can be used your class.
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Lesson 2 Reading Guide Key Concepts ESSENTIAL QUESTIONS
• How are nutrients
processed in the body?
• How does the body
transport and process oxygen and wastes?
• How does the body
How Body Systems Interact
coordinate movement and respond to stimuli?
• How do feedback
mechanisms help maintain homeostasis?
Vocabulary homeostasis negative feedback positive feedback
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Multilingual eGlossary Video
BrainPOP®
Working Together? Have you ever seen a circus aerial act? When people work together, many things can get done. Systems in the human body work together, too. In this lesson, you will learn how important teamwork is for the body.
Chapter 12/Interactions of Human Body Systems
Launch Lab
15 minutes
How can you model homeostasis? The environment around you is constantly changing; however, your body must know how to maintain a delicate balancing act to continue operating. A thermostat in a building helps maintain a constant inside temperature no matter what the outside air temperature is. Like that thermostat, our bodies maintain a constant temperature by sensing the environment and responding. 1 Read and complete a lab safety form. 2 Put one drop of blue food coloring into a beaker
of water. 3 Hold one end of clear, flexible tubing. Have your partner hold the other end of the tubing to form a U shape. Have a third student pour the water into the tubing until it is half full. 4 Place your thumb over one end of the tubing to prevent the water from spilling out. Your
partner should also place his or her thumb over the other end of the tubing. 5 Try several variations of tubing position and observe what happens. Record your
observations in your Science Journal.
Think About This 1. What happened to the level of the water in the tubing as the ends were raised and lowered? 2.
Key Concept What methods do you think your body might use to maintain body temperature on a hot or a cold day?
Homeostasis Did you know that your body has a system to keep its internal temperature constant, much as a thermostat helps keep temperature constant in a building? Most parts of the body function best at 37°C. When temperatures in the body fall below 37°C, you might have goose bumps, as shown in Figure 6. The endocrine system, which regulates body temperature, sends messages through the nervous system. The nervous system signals the muscular system to cause the body to shiver. When you shiver, muscles move. This movement generates thermal energy and helps raise body temperature. Keeping the body’s temperature constant requires that the endocrine system, the nervous system, and the muscular system work together. Your body’s organ systems work together and maintain temperature, nutrient levels, oxygen, fluid levels, pH, and many other types of homeostasis (hoh mee oh STAY sus). Homeostasis is the ability to maintain constant internal conditions when outside conditions change. In this lesson, you will read how organ systems work together and maintain homeostasis.
Figure 6 Goose bumps form when tiny muscles attached to hairs on the skin contract and pull the hairs up straight.
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Processing Nutrients SCIENCE USE V. COMMON USE organ
Science Use a group of tissues performing a specific function
Common Use a keyboard instrument in which pipes are sounded by compressed air
Maintaining homeostasis keeps the internal environment in the body functioning properly. Many organ systems work together and maintain energy homeostasis. Recall that the body gets most of its energy from carbohydrates. Lipids and proteins also provide energy. Food is broken down in the digestive system by chemical and mechanical digestion. Chemical digestion occurs when enzymes in saliva and acid in your stomach break down food. Mechanical digestion happens when you chew your food. The digestive system, the circulatory system, and the muscular system work together and process and obtain nutrients from food. The skeletal system, the endocrine system, and the lymphatic system also work with the digestive system and process those nutrients.
Muscles and Digestion Food enters the body through the digestive system and is broken down into nutrients that can be absorbed into the body. However, the muscular system is needed to get food through the digestive system. Muscles that surround the stomach contract and move food to the small intestine. These contractions, shown in Figure 7, are called peristalsis (per uh STAHL sus).
Figure 7 The muscular system and digestive system work together and process food.
Muscles help the jaw move when you chew. They work with the digestive system and help you swallow. Muscles also surround the esophagus, stomach, the small intestine, and the large intestine and help move food through the digestive system.
Reading Check Where are muscles found in the digestive
system?
Concepts in Motion
Salivary glands
Tongue
Esophagus Liver
Gallbladder Large intestine Rectum
Stomach Pancreas Small intestine
Animation
Chapter 12/Interactions of Human Body Systems
Absorbing Nutrients
Concepts in Motion
Animation
Figure 8 The digestive system and the circulatory system work together and absorb nutrients and move them throughout the body.
Visual Check What does each villus contain?
Folds in small intestine covered with villi
Liver
Gallbladder
Pancreas Small intestine
Blood vessels
Circulation and Digestion You might recall that the small intestine has two important jobs—breaking down food and absorbing nutrients. Two other systems—the muscular system and the circulatory system— work with the small intestine. The muscular system helps the small intestine break down food. The circulatory system works with the small intestine and gets nutrients to the rest of the body. Nutrients are absorbed by small fingerlike projections, called villi (VIH li; singular, villus), in the small intestine. The villi have blood vessels inside them, which are part of the circulatory system, as shown in Figure 8. Nutrients enter these blood vessels and are then transported to the rest of the body. The muscular system also surrounds the blood vessels and helps blood and nutrients move through the body.
Key Concept Check How are nutrients processed in the
body?
Lymph vessel
One villus
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Concepts in Motion
Transporting Oxygen
Blood flow
Blood flow Nose
Bronchiole
Animation
Capillary network on surface of alveolus
Blood flow
Mouth
Pharynx Alveoli
Larynx Trachea
Air in alveolus CO2
Bronchi Lungs
O2
Capillary
Diaphragm
Figure 9 When you inhale, oxygen taken in by the respiratory system enters the circulatory system and is transported to all cells in the body.
REVIEW VOCABULARY cellular respiration a series of chemical reactions that convert the energy in food molecules into a usable source of energy called ATP
Processing Oxygen and Wastes The body cannot function without its systems working together. For example, humans require oxygen to survive. Your lungs take in oxygen and release carbon dioxide. You might recall that all cells in your body use oxygen to help process the energy in nutrients into energy that cells can use. Oxygen helps the body obtain energy from nutrients by performing cellular respiration. Do you know what organ systems work together and help the body take in oxygen and move it through the body?
Reading Check How does oxygen help the body obtain energy?
Oxygen Transport Oxygen enters the body through the respiratory system, as shown in Figure 9. When you inhale, the respiratory system works with the circulatory system and transports oxygen to all cells in the body. The muscular system also helps the respiratory system by expanding your chest so that cells in the lungs fill up with oxygen. Recall that the circulatory system works with the small intestine and moves nutrients into the body. The circulatory system also works with the lungs and helps oxygen travel through the body. Oxygen that is taken in by capillaries, as shown in Figure 9, is transported to the rest of the body through larger blood vessels.
Chapter 12/Interactions of Human Body Systems
Eliminating Wastes The excretory system works with several other organ systems and eliminates wastes. Recall that the body processes food, oxygen, and liquids. Food and liquids are processed by the digestive system. After nutrients are absorbed during digestion, the excretory system removes solid waste products, called feces, through the rectum.
Math Skills
The excretory system also works with the respiratory and circulatory systems and removes carbon dioxide (CO2) from the body. Oxygen is used in all organs of the body. The CO2 produced by cells throughout the body enters capillaries and is transported to the lungs, where it is exhaled. These three systems work together and maintain oxygen homeostasis by making sure that CO2 is removed. The excretory system also maintains fluid homeostasis. Liquid waste travels through the circulatory system to the kidneys, as shown in Figure 10, which make urine. Liquid waste also travels to the skin where fluid is released during sweating.
Key Concept Check How does the body transport and process oxygen and wastes? Figure 10 The kidneys remove liquids, salts, and other wastes from the body by making urine.
Use Volume
Volume is a measure of the amount of matter that a hollow object, such as the stomach or the lungs, will hold. For example, the volume of an empty stomach is about 0.08 L. After eating, a person’s stomach is 1.5 L. What volume of food was consumed? Subtract the starting volume from the final volume. 1.5 L – 0.08 L = 1.42 L
Practice
A certain person’s bladder has a volume of 550 mL. The person has the urge to urinate when the bladder contains 200 mL of urine. What volume of the bladder remains empty? Review
• Math Practice • Personal Tutor
First, water, sugar, salt, and waste pass from the capillaries into small tubes.
Kidney
Cluster of capillaries
Ureter Bladder Urethra
Ureter Collecting duct Second, water and nutrients pass from the small tubes into the blood vessels that surround them.
Third, urine travels through the collecting duct to the ureter.
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Control and Coordination Have you ever wondered how your heart beats without you thinking about it? The heart contains a group of specialized cells called pacemaker cells. These cells control the rate at which the heart beats by responding to signals from the nervous system. When exercising, the nervous system speeds up the heartbeat. When sleeping, the nervous system slows the rate at which the heart beats. The nervous system also works with other organ systems and controls the body’s functions. The nervous system uses electrical signals and helps organ systems of the body respond quickly to changes in the internal and external environments. The body also uses the endocrine system to help it respond to changes and maintain homeostasis. The nervous system coordinates rapid changes, and the endocrine system coordinates slower responses.
Key Concept Check How does the body coordinate movement and respond to stimuli?
Sensory Input
Your pupils Figure 11 increase in size when you enter a darkened room.
Visual Check When
does the iris contract?
The nervous system coordinates the body’s response to external stimuli. For example, when you dim lights to watch a movie, your pupils change in size, as shown in Figure 11. The nervous system also coordinates your response to the sight, the smell, the touch, and the taste of popcorn. The nervous system works with the respiratory and muscular systems to detect the popcorn’s aroma. It coordinates muscles in the eyes to see the popcorn. The nervous system also works with the digestive system and prepares for eating the popcorn by producing saliva. It also coordinates the digestive and muscular systems so that the popcorn is broken down and moved through the body. Iris
Pupil
The iris contracts in dim light. Iris
Pupil
The iris expands in bright light.
Chapter 12/Interactions of Human Body Systems
Reflexes Recall that the nervous system uses electrical signals, coordinates responses to stimuli, and signals other organ systems. Neurons send electrical signals to the brain for processing so the nervous system can coordinate a response. However, when a person touches a hot stove, the nervous system coordinates the response so quickly that the brain does not first process information about the hot stove. In fact, the response to touching a hot stove is so fast that thought is not required before the person removes his or her hand. This is because the nervous system has a rapid response system, called a reflex, that reacts to stimuli without sending information to the brain for processing. Reflexes allow the nervous system to coordinate a rapid response and tell the muscular system and skeletal system to move without thought.
Hormones The nervous system coordinates the responses of other organ systems by using electrical signals. The endocrine system coordinates other organ systems by using chemical signals called hormones. Hormones are secreted from endocrine organs such as the thyroid gland, the adrenal gland, and the pancreas.
MiniLab
20 minutes
Is the hand quicker than the eye? Your body sometimes can play tricks on you. When you look at something, the optic nerve sends a message to your brain. This experiment will explore how the body responds to a stimulus with the optic nerve and sometimes misinterprets what is seen. 1 Read and complete a lab safety form. 2 Using an index card folded in half, draw a
bird on one side and a bird cage on the other side with a permanent marker. Both pictures should be drawn in the center of the card. Be sure to make the cage big enough so the bird can fit inside. 3 Slip the folded card over the pointed end
of a pencil. The point should break through the card slightly. Tape both sides of the card to the pencil.
4 Twirl the pencil back and forth rapidly. 5 In your Science Journal, record what you
see happening.
Reading Check What are hormones? These chemical signals travel through the circulatory system to organ systems such as the digestive and muscular systems. They also control processes that maintain homeostasis. In the beginning of this lesson, you read that temperature homeostasis is maintained by producing thermal energy. The endocrine system, the nervous system, and the muscular system work together and maintain temperature homeostasis. Insulin, a hormone released from the pancreas, works with the digestive system and maintains energy homeostasis.
Analyze and Conclude 1. Describe What happened to the bird as you twirled the pencil? 2. Draw Conclusions What body functions worked together to see the illusion? Discuss real-world applications. 3.
Key Concept How does the body respond to a stimulus?
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Feedback Mechanisms ACADEMIC VOCABULARY detect
(verb) to identify the presence of something
As you have read, homeostasis helps the body maintain a constant internal environment. The endocrine and nervous systems help detect changes in either the internal or the external environment and respond to those changes. Organ systems use feedback mechanisms to maintain homeostasis.
Negative Feedback
Make a two-tab horizontal matchbook. Label it as shown. Use it to compare types of feedback.
–
–
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–
Feedback
Negative feedback is a control system that helps the body maintain homeostasis by sending a signal to stop a response. Negative feedback is used when you are hungry because the digestive system receives signals that it is time to eat. When you eat, the digestive and circulatory systems then work together and increase the amount of nutrients in the body. As the nutrients are being processed, the stomach sends signals to the brain to tell the body that you are full and to stop eating.
Positive Feedback In contrast to negative feedback, positive feedback is a control system that sends a signal to increase a response. Blood clotting is an example of positive feedback. When you are bleeding, the circulatory system maintains homeostasis by controlling blood loss. Blood cells called platelets move to the site of the wound and help control bleeding by forming a clot with a protein called fibrin, as shown in Figure 12. As the clot forms, more platelets travel to the clot and help control the bleeding. Childbirth is also an example of positive feedback. The endocrine system signals the muscular system to contract. Signals from the muscular system tell the endocrine system to keep activating the muscular system until the baby is born.
Key Concept Check How do feedback systems help maintain homeostasis?
Figure 12
The body uses positive feedback to clot blood.
Step 1 Platelets rush to the tear and form a plug that stops the bleeding.
Step 2 A web of fibrin forms around the platelets and holds them in place.
Concepts in Motion
Animation
Step 3 The fibrin web catches more platelets and red blood cells, and these form a blood clot.
Chapter 12/Interactions of Human Body Systems
Lesson 2 Review Visual Summary
Online Quiz
Assessment
?
Inquiry
Virtual Lab
Use Vocabulary 1 Distinguish between negative feedback and positive feedback. Muscles that surround the stomach help move food to the small intestine.
2 The ability to maintain a constant environment in the body is
.
3 Use the term positive feedback in a sentence.
Understand Key Concepts Iris
4 Which system sends electrical signals?
Pupil
The nervous system coordinates the body’s response to external stimuli.
A. endocrine B. muscular
C. nervous D. respiratory
5 Explain the role of the muscular system in maintaining temperature homeostasis. 6 Describe how the muscular system helps substances such as nutrients and oxygen travel through the body.
When you are bleeding, the circulatory system maintains homeostasis by controlling blood loss.
Use your lesson Foldable to review the lesson. Save your Foldable for the project at the end of the chapter.
Interpret Graphics 7 Summarize Copy the graphic organizer below. Use it to show how organ systems work together and process nutrients and remove food waste from the body.
Process nutrients and wastes
Critical Thinking What do you think
8 Evaluate which body systems are working together in the figure shown below.
You first read the statements below at the beginning of the chapter.
4. Nutrients are processed by the skeletal system.
5. The nervous system moves oxygen through the body.
6. You do not control reflexes. Did you change your mind about whether you agree or disagree with the statements? Rewrite any false statements to make them true.
Math Skills
Review
Math Practice
9 During normal breathing, the average human inhales about 0.5 L of air per breath. If a person takes 15 breaths per minute, what volume of air does the person inhale in 1 min?
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Lab Materials
stopwatch
thermometer Also needed: other materials approved by your teacher
2 Class Periods
How can a stimulus affect homeostasis? Have you ever been on a roller coaster? Most people love the thrill and excitement of an amusement park ride. As the ride speeds up, slows down, and spins around, your heart races, you catch your breath, and goose bumps form on your arms. Because of outside stimuli, your body systems work overtime to keep homeostasis. This experiment will give you an opportunity to test the results of stimuli on yourself and your classmates.
Ask a Question How does a stimulus affect your body?
Make Observations 1 Read and complete a lab safety form.
Safety
2 With your lab team, brainstorm a list
of stimuli that affect the human body, such as a hearing a loud noise or viewing a roller coaster ride. From this list, select one stimulus that appeals to the group. 3 Create a plan to introduce the same
stimulus to each member of your group. Make sure to get your teacher’s approval before proceeding. 4 Copy the data table below in your Science Journal. 5 Sit quietly for 1 min. Measure your heart rate, your breathing rate, and your
temperature. Record the measurements in your table. Also be sure to note the status of body systems, such as skin color, saliva production, and sweating, that might be affected by the stimulus.
Measurement Heart rate Breathing rate Temperature
Before Stimulus
10 Min After After Stimulus Stimulus
Chapter 12/Interactions of Human Body Systems
Form a Hypothesis 6 Based on your knowledge of the stimulus you
selected, form a hypothesis about the effect of your stimulus on heart rate, breathing rate, and body temperature.
Test Your Hypothesis 7 Introduce the selected stimulus to each
member of your team. 8 Immediately after the stimulus has been
completed, measure your heart and breathing rates and your body temperature. Record the data. Note any changes in the other systems you were watching, and record their statuses. 9 Sit quietly for 10 min. Measure and record your
heart rate, your breathing rate, and your body temperature. 10 Graph the results of all three intervals for each
category—heart rate, breathing rate, and body temperature.
Lab 4HOR Heart and breathing rates are measured in occurrences per minute. Make sure all students are tested as uniformly as possible.
Analyze and Conclude 11 Examine the data from the procedure. How
did your body respond to the stimulus? Was your hypothesis correct? 12 Analyze what happened to your heart rate,
your breathing rate, and your body temperature during the experiment. 13
The Big Idea Explain how your results relate to homeostasis.
Communicate Your Results Design a 30-second news flash skit to announce your results in a creative way. Have each team member take part in the presentation.
Extension How do you think an athlete’s body would respond to your stimulus? Could diet play a role? Explore how environment and lifestyle could alter the body’s response to a stimulus and affect homeostasis.
Remember to use scientific methods. BV`ZDWhZgkVi^dch 6h`VFjZhi^dc ;dgbV=nedi]Zh^h IZhindjg=nedi]Zh^h ana 6cVanoZVcY8dcXajYZ 8dbbjc^XViZGZhjaih
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Chapter Guide Chapter12 Study Study Guide
WebQuest
Human body systems are organized into systems that work together and maintain homeostasis.
Key Concepts Summary
Vocabulary
Lesson 1: The Human Body
macromolecule
• Inorganic compounds are required + + for human body systems to function. + Water is a universal solvent and + - + + essential for life. + + + - + + + • Organic compounds contain + carbon and are essential to + - + + support life. Macromolecules are + + + + organic compounds that make up + + + all cells. + + + • The body’s organization plan helps + groups of organs that perform the same function work together.
monosaccharide
Lesson 2: How Body Systems Interact
homeostasis
• Nutrients are processed when the digestive, muscular, and circulatory systems work together. • The respiratory, circulatory, muscular, and digestive systems work together and process oxygen and remove wastes from the body. • The nervous system communicates with the muscular and skeletal systems and coordinates movement and responds to stimuli. • Feedback mechanisms help the body maintain homeostasis by turning off a response or activating more of the response.
negative feedback
amino acid nucleotide
positive feedback
Chapter 12/Interactions of Human Body Systems
Study Guide
• Personal Tutor • Vocabulary eGames • Vocabulary eFlashcards
Use Vocabulary
Chapter Project
1 Lipids, proteins, carbohydrates, and nucleic acids are all .
Assemble your lesson Foldables as shown to make a Chapter Project. Use the project to review what you have learned in this chapter.
2 DNA and RNA are made of
.
3 Write the definition of amino acids in your own words.
–
–
Feed back
l to Life Essentia
Review
4 Use the term negative feedback in a sentence. 5 Use the term homeostasis in a sentence.
Water
6 When a response causes more of a response, is occurring.
s of Human Body Syst n o i t c a ems Inter
Concepts in Motion
Link Vocabulary and Key Concepts
Interactive Concept Map
Copy this concept map, and then use vocabulary terms from the previous page and other terms from the chapter to complete the concept map. 10
ion
9
fO rga
11
Organ System
Le
s
8
ve ls o
ule
lec mo
niz
cro
7
Tissue
at
Ma
Carbohydrates
12
th at Pro ce ss Sys tem s
14
Respiratory Muscular
en yg Ox ort nsp Tra at th
13
s tem Sys
Digestive
Nu tri en ts
The Human Body
15
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Chapter 12 Review Chapter Review Understand Key Concepts 1 Which macromolecule does NOT dissolve in water? A. B. C. D.
carbohydrate lipid nucleic acid protein
2 Which CANNOT be broken down into smaller parts? A. B. C. D.
6 What is formed in the figure below?
compounds elements macromolecules water
3 What is the structure shown below?
A. B. C. D.
carbohydrate lipid nucleic acid protein
7 What is the smallest living unit of the human body? A. B. C. D.
cell organ system tissue
8 What are chemical signals produced by the endocrine system called? A. B. C. D. A. B. C. D.
amino acid DNA monosaccharide triglyceride
4 What is NaCl? A. B. C. D.
an element a lipid an inorganic compound an organic compound
5 Which organ system works with the excretory system to remove carbon dioxide? A. B. C. D.
circulatory digestive endocrine nervous
hormones reflexes ionic compounds nucleic acids
9 The muscular system and the nervous system work together and A. B. C. D.
coordinate movement. digest food. process oxygen. transport blood.
10 Which organ system is NOT used to obtain nutrients from food? A. B. C. D.
circulatory digestive muscular respiratory
11 Blood clotting is an example of A. B. C. D.
a hormonal response. negative feedback. positive feedback. a reflex response.
Chapter 12/Interactions of Human Body Systems
Chapter Review
Assessment
Online Test Practice
Critical Thinking 12 Summarize how the body’s organization helps it function. 13 Compare the compositions and functions of carbohydrates and lipids. 14 Relate the structure of the molecule shown below to its ability to dissolve ionic compounds.
REVIEW 21 Assess how the nervous system interacts with other organ systems and coordinates responses to the external environment. 22 How do human body systems in the lungs interact and support life?
+ + 15 Summarize the role of carbon in enabling the body to function. 16 Relate the two functions of the small intestine to obtaining nutrients from food. 17 Evaluate the effect of anhydrosis, the inability to sweat, on temperature homeostasis. 18 Compare the roles of the circulatory system in obtaining nutrients and wastes. 19 Relate homeostasis to negative feedback.
Math Skills
Review
Math Practice
Use Volume 23 The average human stomach ranges from a volume of 0.08 L empty to 4 L full. What is the total volume of food and gastric secretions required to fill the stomach? 24 A person consumes 2 L of fluid per day. If the person urinates a total of 1,400 mL in 24 h, what volume of liquid is lost in other ways or retained in the body? (Hint: 1 L = 1,000 mL)
20 Write a five-sentence paragraph that describes how organ systems interact to carry out functions in the body. Be sure your paragraph includes an example of how organ systems interact to carry out a specific function.
25 Normal feces are about 75% solid and 25% water. If the volume of a person’s feces is 0.6 L, what is the volume of water in the feces? (Hint: What is 25% of 0.6 L?)
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Standardized Test Practice Record your answers on the answer sheet provided by your teacher or on a sheet of paper.
Multiple Choice 1 Which ion is found in bone and plays a role in nerve and muscle cell function? A calcium (Ca2+) B chloride (Cl–) C fluoride (F–) D sodium (Na+) 2 Which is NOT a function of proteins?
5 The digestive system and the circulatory system work together and absorb nutrients in which structure? A alveolus B kidney C thyroid D villus Use the figure below to answer question 6.
A to dissolve ionic substances B to give cells structure C to help cells communicate D to serve as enzymes Use the figure below to answer question 3.
6 The figure above shows a step in moving food through the body. Which body systems are involved in this step? A digestive and respiratory B muscular and circulatory C muscular and digestive D skeletal and respiratory
3 The macromolecule shown in the figure belongs to which class of compounds? A carbohydrates
7 Which systems work together and transport oxygen and carbon dioxide through the body?
B lipids
A circulatory and respiratory
C nucleotides
B digestive and excretory
D proteins
C endocrine and nervous
4 Which organs help maintain fluid homeostasis? A heart and kidneys B kidneys and skin C lungs and heart D skin and lungs
D muscle and skeletal
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Chapter 12/Interactions of Human Body Systems
Standardized Test Practice
Assessment
Online Standardized Test Practice
Constructed Response
Use the figure below to answer question 8.
Use the figure below to answer questions 11 and 12.
Renal artery
Renal vein Ureter
11 Use the figure above to explain how the human body is organized into four levels. Identify and define each level in your response.
8 Which body systems are linked by the role of the organ shown in the figure? A circulatory and digestive B digestive and respiratory
12 Based on the figure, describe the four levels of organization in the circulatory system. Give an example of structures at each level.
C excretory and circulatory D skeletal and excretory 9 Which body systems help the body respond to stimuli?
13 Explain how the body responds to increases and decreases in temperature. Are these responses negative or positive feedback?
A circulatory and respiratory B digestive and excretory C endocrine and nervous D immune and skeletal
14 Polio is a disease of the nervous system that paralyzes muscles. In the midtwentieth century many children contracted polio. Some died because they could not breathe. Use your knowledge of the interactions between body systems to explain how polio could affect breathing.
10 Which is a major role of water in the body? A It forms cell membranes. B It joins together amino acids. C It stores information in the body. D It transports ions through the body.
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