Download Interactions of Human Body Systems

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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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Assessment
Review
Concepts in Motion
Inquiry
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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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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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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
Skin Graft
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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
g
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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iScience Grade 7, Davis County Edition
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.
–
–
414
–
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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iScience Grade 7, Davis County Edition
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.
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417
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iScience Grade 7, Davis County Edition
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
419
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iScience Grade 7, Davis County Edition
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?)
421
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iScience Grade 7, Davis County Edition
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
423
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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