LESSON 5

Body Systems

Control and Information Processing

Key Concept
• How do living things
What do you think? Read the two statements below and decide control body functions,
whether you agree or disagree with them. Place an A in the Before and how do they process
column if you agree with the statement or a D if you disagree. After information?
you’ve read this lesson, reread the statements to see if you have
changed your mind.
Before Statement After
The nervous system has only one part, which
works independently of other body systems.
The senses of smell and hearing work together.

Study Coach

What controls the body’s functions? K-W-L Fold a sheet of

paper into three columns.
Have you ever had goose bumps on your arms when you were
Label them (K) what you
cold? When you encounter cold temperatures, the muscle cells in know about the nervous
your skin contract. Then bumps form, and the hairs on your arms system, (W) what you want
rise up and trap air. The trapped air insulates your skin and helps to learn, and (L) the facts
you feel warmer. How do your muscle cells know to contract? that you learned. Fill in the
third column after you have
The Nervous System When you first feel the cold, a message read this lesson.
is sent to your brain, which is part of your nervous system. Your
brain then sends a message to your skin’s muscle cells, and the Scientific Vocabulary
insulate
Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use.

goose bumps form. The nervous system is the part of an

(verb) to cover or protect
organism that gathers, processes, and responds to information.
to keep heat from getting
The basic functioning units of the nervous system are called in or out
nerve cells, or neurons (NOO rahnz). A neuron is shown in the
figure on the next page. Neurons help different parts of your
body communicate with each other.
Your nervous system gets information from your five senses.
Sense receptors respond to changes in the environment. They
send signals to the brain. The brain is the control center of the
body. Your brain receives information and processes it. Then it
sends out a response. Your brain also stores some information as
memories.

Reading Essentials Body Systems  27

THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.
 Brain

Spinal
cord

Peripheral
nerves

Neuron

Central nervous system (CNS)

Peripheral nervous system (PNS)
RE_L240_501A_NGMSS-BANK
Academic Vocabulary The nervous system reacts quickly. It can receive information,
respond process it, and respond in less than one second. Signals received
(verb) to do something RE_L240_512A_NGMSS-BANK
by the nervous system can travel as fast as some airplanes. This
as a reaction to something is around 400 km/h (249 mi/h)!
else
Your nervous system has two parts: the central nervous
system and the peripheral (puh RIH frul) nervous system. These
systems are shown in the figure above. The central nervous
system (CNS) is made up of the brain and the spinal cord. The
Word Origin
CNS receives, processes, stores, and transfers information.
neuron The spinal cord is a tubelike structure of neurons. You read

Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use.

from Greek neuron, earlier that a neuron is a nerve cell that sends and receives
means “a nerve cell with information in your body. Because the neurons extend to other
appendages” areas of the body, the brain can send out and get information.
The spinal cord can be thought of as an information highway
between the brain and the rest of the body. Cars use a highway
to move quickly from one city to another. Similarly, neurons in
the spinal cord send information quickly back and forth
between the brain and other body parts.

28  Body Systems Reading Essentials

THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.
 The peripheral nervous system (PNS) has sensory neurons Word Origin
and motor neurons that transmit information between the CNS sensory
and the rest of the body. The PNS has two parts: the somatic from Latin sentire, means
system and the autonomic system. “to perceive, feel”

The somatic system controls skeletal muscles. Neurons of the

somatic system communicate between the CNS and skeletal
muscles. They cause voluntary movements, such as kicking a
ball and picking up a book. The autonomic system controls
smooth muscles and cardiac muscles. It regulates involuntary
actions, such as the beating of your heart.

How does your body receive

information?
Your nervous system constantly receives information from
your external environment and from inside your body. It can
receive information, process it, and respond in less than 1
second. However, your body has to receive a stimulus before it
can respond to one. How does your body do this?
The Senses The sensory system is the part of your nervous
system that detects or senses the environment. People use five Academic Vocabulary
senses to detect their environment. They are vision, hearing, detect
smell, touch, and taste. There are also other senses, such as your (verb) to identify the
sense of balance and sense of direction. Receptors are special presence of something
structures that detect stimuli. All parts of the sensory system
have receptors. Each of your five senses detects things about Scientific Vocabulary
your environment. They do this by using different receptors. stimuli
(noun) something that
causes a change or reaction
How does your body receive
information through taste and smell?
Suppose that you do not want to taste something that you
Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use.

are eating or drinking. What could you do to block the taste?

Some people hold their nose. Does this really work? Your senses Scientific Vocabulary
function because of nervous impulses that send information. impulse
(noun) small amount of
Are your senses of taste and smell connected? The answer is energy that moves from
yes. You can smell food even if you cannot taste it. You can taste one area to another
food, at least a little, even if you cannot smell it. However, you
get the most information about food if you can both smell and
taste it.

Reading Essentials Body Systems  29

THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.
 Taste and Smell With your eyes closed, you can tell the
difference between an orange and a rotten egg. You can do this
because of your sense of smell. Humans have hundreds of
different receptors that detect odors, or smells. Some dogs have
more than 1,000 different odor receptors.
Odors are molecules that chemical receptors in your nose can
detect. These chemical receptors are called chemoreceptors (kee
moh rih SEP turz). They send messages to your brain about
odors. Your brain processes the information about odors. A
smell might make you feel hungry. A smell might trigger a
memory or feeling.
Your sense of taste also uses chemoreceptors. Chemoreceptors
on your tongue are called taste buds. When taste buds detect
food or drink, they send messages to the brain to be processed.
Your senses of taste and smell work together to help you taste
your food. Chemoreceptors detect the stimuli for taste and smell.
They send messages to the brain, which processes them into
memories. For example, you will remember the smell of spoiled
milk. Your brain might also direct your body to perform an
action. For instance, you might immediately spit out rotten food.

How does your body receive

information through touch?
Scientific Vocabulary Your skin has millions of nerve endings. Some parts of the
sensitive skin are more sensitive to touch. The skin registers different
(adjective) able to feel very sensations.
small changes or light touch
Touch Like all the other senses, the sense of touch uses special
receptors to detect the environment. Touch receptors are in your
skin. They can detect temperature, pain, and pressure. Touch
receptors send signals to the brain for processing. Touch

Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use.

receptors are all over your body. Some areas have lots of
receptors. The palms of your hands and the soles of your feet are
in this category. Other areas, such as the middle of your back,
have fewer receptors.
Just like the other four senses, touch receptors send
messages to the brain. The brain processes information and
creates memories. For example, suppose you touch something
hot and burn your hand. Your brain will remember how this felt.

30  Body Systems Reading Essentials

THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.
 How does your body receive Scientific Vocabulary
vibration
information through sound? (noun) a series of fast
You already know that your ears allow you to hear, but how movements back and forth
exactly does hearing work? Like the other senses, hearing
requires sense receptors. Scientific Vocabulary
wave
Hearing To hear sound, you need auditory (AU duh tor ee)
(noun) a disturbance in a
receptors. The vibration of matter creates sound waves. These material that transfers
waves travel through air and other substances. Sound waves that energy without
enter your ears are detected by auditory receptors. transferring matter
As sound waves travel through your ears, they are amplified,
or increased. The sound waves move hair cells in the inner part Scientific Vocabulary
of the ears. Hair cells send information about the sound waves auditory
(adjective) related to
to your brain. The brain processes information about the
hearing or the ears
loudness and tone of the sound, and you hear. The inner ear
also helps you maintain balance.
Academic Vocabulary
maintain
How does your body receive (verb) to make something
information through sight? stay the same
Your sense of vision lets you see things that are close, such as
the words on this page. It also lets you see things that are far
away, such as the stars in the night sky. Your eyes contain
photoreceptors that sense light and create vision. As shown in
the figure below, the photoreceptors are located at the back of
the eye.

2 Light passes through

the pupil, an opening in
1 Light enters the eye the iris.
Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use.

through the cornea.

3 Light rays are focused
as they pass through the
lens.

Pupil

Cornea

4 The light is focused

Iris onto the retina at the
Lens Retina back of the eye, and an
image forms.

Reading Essentials Body Systems  31

THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.
RE_L240_516A_NGMSS-BANK
 Vision The eye has many specialized parts. Light enters the eye
through the cornea (KOR nee uh). This thin membrane protects
the eye. The cornea also changes the direction of light rays.
Light goes through the pupil, an opening in the iris (I rus).
The iris is the colored part of your eye. It controls how much
light enters your eye by changing the size of the pupil. In bright
light, your iris constricts. Your pupil gets smaller. Less light is let
into your eye. When there is little light, your iris relaxes. Your
pupil gets larger. More light is let into your eye.
Light then travels through the lens. The lens is a clear
structure. It works with the cornea to focus light. Light rays are
focused onto the retina (RET nuh), where an image forms. The
retina is an area at the back of the eye. The retina has two types
of cells—rod cells and cone cells—with photoreceptors.
Science Use v. Common Use In order to see, light that enters your eyes has to be detected
rod by the rods and cones in your retina. The rods and cones detect
Science Use one of the information about the colors and shapes of objects from the
photoreceptors in the eye light that enters your eyes. The retina then sends that
that picks up the shape of
information as electric signals through the optic nerve to the
objects
brain. In the brain, the information is processed. The brain uses
Common Use any long, the information. It creates a picture of what you are seeing.
cylinder-shaped object

How do plants respond to stimuli?

Humans and animals use their senses to receive information
from their environment. Their sense receptors detect changes in
the environment. Their nervous systems are triggered, and they
react. Plants, too, are able to respond to their environment.
Plant Responses to Stimuli Plants respond to many stimuli in
their environment. However, it might be hard for humans to see a
plant’s response. This is because the response might happen slowly.

Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use.

Light is a stimulus. A plant responds to light by growing
Word Origin toward it. This response occurs over several hours. Gravity is
stimulus also a stimulus. Plant roots respond to gravity by growing
from Latin stimulare, downward, toward the center of Earth. This response continues
means “goad, urge” over the life of the plant.
Some plants respond quickly to stimuli. An example is the
Venus flytrap. When an insect touches the plant, two of its leaves
snap together. The insect is trapped inside. The plant digests it.

Reread the statements at the beginning of the lesson. Fill in

the After column with an A if you agree with the statement or a
D if you disagree. Did you change your mind?

32  Body Systems Reading Essentials

THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.