Chapter 20: The Nervous and Endocrine Systems · 2019-11-07 · Nervous and Endocrine Systems...

544B

Chapter Review, pp. 39–40Assessment, pp. 77–80Performance Assessment in the Science

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National ContentStandards: UCP2,A1, C1

Activity Worksheets, pp. 109–110Enrichment, p. 55 Laboratory Manual, pp. 117–120 Multicultural Connections, pp. 39–40 Reinforcement, p. 55 Study Guide, pp. 77-78

Activity Worksheets, pp. 111–114 Enrichment, p. 56 Home Involvement, p. 28Laboratory Manual, pp. 121–124 Reinforcement, p. 56

Critical Thinking/Problem Solving, p. 20Enrichment, p. 57 Reinforcement, p. 57 Study Guide, pp. 79–80

Section Focus Transparency 55 Teaching Transparency 39Glencoe Science VoyagesInteractive CD-ROMInternet Connection, p. 551

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Assessment Resources

Level 1 activities should be appropriate for students with learning difficulties.

Level 2 activities should be within the ability range of all students.

Level 3 activities are designed for above-average students.

ELL activities should be within the ability range of English Language Learners.

Cooperative Learning activities are designed for small group work.

These strategies represent student products that can be placed into a best-work portfolio.

Multiple Learning Styles logos, as described on page 63T, are used throughoutto indicate strategies that address different learning styles.

P

COOP LEARN

ELL

L3

L2

L1

The following designations will help you decide which activities are appropriate for your students.

Key to Teaching Strategies

English and Spanish audiocassettes areavailable for use with each section.

Test Practice Workbooks are available foruse with each chapter.

California ScienceContent Standards:5a, 5b, 7a, 7b, 7c

California ScienceContent Standards:5a, 5b, 5g, 6c, 6d,6e, 7a, 7c, 7e

California ScienceContent Standards:5a, 5b, 7b, 7c

Chapter 20

544A CHAPTER 20 NERVOUS AND ENDOCRINE SYSTEMS

Section Objectives Activities/Features

Activity MaterialsExplore Activities MiniLabs

Chapter 20 Nervous and Endocrine Systems

Chapter Opener

20-1The Nervous System

3 Sessions11⁄2 Blocks

20-2The Senses

3 Sessions11⁄2 Blocks

20-3The Endocrine System

1 Session1⁄2 Block

1. Describe the basic structure of a neuronand how an impulse moves.

2. Compare the central and peripheral nervoussystems.

3. Explain how drugs affect the body.

4. List the sensory receptors in each senseorgan.

5. Explain what type of stimulus each senseorgan responds to and how.

6. Explain the need for healthy senses.

7. Explain the function of hormones.8. Name three endocrine glands and explain

the effects of their hormones.9. Explain how a feedback system works.

Explore Activity: Observe Objects, p. 545

Physics Integration, p. 549Using Math, p. 550Skill Builder: Concept Mapping, p. 552Using Computers, p. 552Activity 20-1: Reaction Time, p. 553

MiniLab: Observing Balance Control, p. 555Using Math, p. 556MiniLab: Comparing Sense of Smell, p. 558Skill Builder: Observing and Inferring, p. 559Science Journal, p. 559Activity 20-2: Investigating Skin Sensitivity,

pp. 560–561

Problem Solving: Interpreting Blood SugarLevels, p. 563

Skill Builder: Comparing and Contrasting, p. 564

Science Journal, p. 564How It Works: A Hearing Aid, p. 565

p. 545metric ruler

p. 553metric ruler

pp. 560–5613 � 5 index cards, toothpicks, glue or tape, metric ruler

p. 555paper, masking tape

p. 558different types of food, colognes,or household products, cottonballs

The number of recommended single-period sessions The number of recommended blocksOne session and one-half block are allowed for chapter review and assessment.

Need Materials? Contact Science Kit at 1-800-828-7777 or at www.sciencekit.com on the Internet. For alternate materials, see the activity on the listed page.

Study Guide, p. 78

http://www.sciencekit.com

Critical Thinking/Problem Solving

NAME DATE CLASS

Chapter 22

CRITICAL THINKINGThe Nervous and Endocrine Systems

Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.22

When working properly, your endocrineglands secrete hormones into your blood. Thehormones are then carried throughout yourbody. When the correct amount of a hormonereaches its target tissue, it causes certain reac-tions in that organ or tissue. But sometimes,too much or too little hormone is released.

Some congenital defects can cause low hor-mone levels. Congenital means “at birth.”When some babies are born, they have a prob-lem with enzymes that produce hormones.Unless this is noticed and treated early, suchbirth defects can cause severe brain damage.

Some of these defects can be detected beforethe newborn leaves the hospital. A screeningtest is usually done by drawing a smallamount of blood from the baby’s heel.Congenital hypothyroidism is one birth defectcommonly screened for. Congenital hypothy-roidism is a disease of the thyroid gland. Thethyroid gland does not secrete enough thyroidhormones. This condition affects growth andbrain development. An infant with this condi-

tion will have dry, wrinkled skin, an enlargedtongue, a broad face, and a slow heartbeatrate. Children are short for their age and arementally retarded. Adults with hypothy-roidism are dwarfs. If the condition is foundearly enough, these defects may be prevented.An infant known to have a thyroid deficiencyis treated with hormones.

Many diseases of endocrine glands arecaused by tumors. The tumors may cause thegland to either produce too much or notenough of a hormone. Gigantism, oracromegaly, is caused by a tumor on the pitu-itary gland. In this case, the tumor causes thegland to produce too much growth hormone(GH). GH controls the growth of bones. If aperson has a tumor on the pituitary glandduring childhood, he or she may growextremely tall (up to 7 to 9 feet). If treatedearly, gigantism can be controlled by slowingthe release of GH by the pituitary with radia-tion treatment. Sometimes, the tumor can beremoved surgically.

Applying Critical Thinking Skills1. Why is it important for pregnant women to know about congenital defects?

2. Why do excess amounts of growth hormone cause people to grow extremely tall?

3. Which endocrine gland of “André the Giant,” the professional wrestler, was probably not functioning properly?

Diseases of the Endocrine System

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Accessibility

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Spanish Resources

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Hands-on Activities

Lab ManualActivity Worksheets

Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 121

NAME DATE CLASS

Chapter 22

ACTIVITY 22-1 Reaction Time

What You’ll InvestigateHow can reaction time be improved?

Goals• Observe reflexes.• Identify stimuli and responses.

Materials• metric ruler

Procedure1. Review the data table below.

2. Have a partner hold the ruler at the topend.

3. Hold the thumb and finger of your righthand apart at the bottom of the ruler. Donot touch the ruler.

4. Your partner must let go of the ruler with-out warning you.

5. Try to catch the ruler by bringing yourthumb and finger together quickly.

6. Repeat this activity several times andrecord where the ruler was caught in a data table.

7. Repeat this activity with your left hand.Record your results.

Lab Preview1. What are two major divisions of the human nervous system? central (CNS) and

peripheral (PNS)

2. Which system is used when the body reacts to a stimulus? Both are used.

Your body responds quickly to some kinds of stimuli, and reflexesallow you to react quickly, without even thinking. Sometimes you canimprove how quickly you react. Complete this activity to see if youcan improve your reaction time.

Sample Data for left-handed person

Where the Ruler Was Caught

Trial Right Hand Left Hand

1 30 20

2 20 10

3 15 10

L2Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 123

NAME DATE CLASS

Chapter 22

LABORATORY MANUALWhich brain side isdominant? 43

The human brain is divided into a left and a right side. Many things that you do with the rightside of your body are controlled by your brain’s left side. Many things that you do with the leftside of your body are controlled by your brain’s right side. If much of what you do is done byyour body’s right side, your dominant brain side is the left side. If much of what you do is doneby your body’s left side, your dominant brain side is the right side.

StrategyYou will check to see how many activities you do using your left hand or your right hand.You will check how many activities you do using your left foot or your right foot.You will find out if you draw or see objects more to the right side or the left side.You will find out if the left side or the right side of your brain is dominant.

Materials paperred pencil

Procedure1. Place a check mark in the proper column in Table 1 to show which hand you usually use to do the

following tasks. Note: If you use either hand just as often, then check both columns.Tell which hand you use toa. write your name.b. wave “hello.”c. bat while playing baseball.d. place on top when folding your hands.e. hold your spoon or fork while eating.

2. Place a check mark in the proper column in Table 1 to show which foot you usually use to do thefollowing tasks. Note: If you use either foot just as often, check both columns.Tell which foot you use toa. start down a flight of stairs.b. start up a flight of stairs.c. catch yourself from falling as you lean forward.d. start skipping.e. place most weight on when you are standing.f. start to run.g. kick a ball.

3. Draw, in the space provided, a simple side view of a dog. Place a check mark in the column inTable 1 that shows the direction the nose faces.

4. Draw a circle in the space provided with your right hand. Note the direction in which you madethis circle. Now draw a circle with your left hand. Note the direction in which you made this circle.If both circles were drawn clockwise, mark the right column in Table 1. If both circles were drawncounterclockwise, mark the left column in Table 1. If you drew one circle in each direction, checkboth columns.

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Hands-on Activities

Chapter Review

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Part A. Vocabulary ReviewWrite the correct term in the space beside each definition.

1. connects brain to spinal cord ______________________________

2. conducts messages to neuron cell body ______________________________

3. neurons that move impulses from the brain ______________________________

4. functioning unit of nervous system ______________________________

5. brain part maintaining muscle tone ______________________________

6. eye tissue made up of rods and cones ______________________________

7. fluid-filled structure in inner ear ______________________________

8. brain part divided into hemispheres ______________________________

9. cells that aid in the sense of smell ______________________________

10. endocrine secretions ______________________________

11. move messages away from neuron cell body ______________________________

12. neurons that move impulses to the brain ______________________________

Complete the following sentences using the correct terms.

13. The space between one neuron and the next is a __________________________.

14. The system made up of the brain and spinal cord is the___________________________.

15. The ______________________________has two systems using cranial and spinal nerves.

16. ___________________________are nerve cells throughout the brain and spinal cord that relayimpulses from sensory neurons to motor neurons.

17. Hormones affect specific tissues called ______________________________.

Study the following diagram, and label the parts of the brain shown.

NAME DATE CLASS

Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

The Nervous and Endocrine Systems

Chapter 22

CHAPTER REVIEW

brain stem

motor

neuron

dendrites

cerebellum

retina

2/22:1

2/22:1

1/22:1

1/22:1

1/22:1

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cochlea

cerebrum

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sensory

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1/22:1

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2/22:1

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synapse

central nervous system

peripheral nervous system

Interneurons

target tissues

cortex

cerebrum

midbrain

brain stem

medulla

pons

cerebellum

spinal cord

1/22:2

20.

21.

18.

19.

24.

25.

22.

23.

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Performance Assessment

Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.36

Optical illusions are mistaken ideas based on the sense of vision. What you see and what you thinkyou see are not always the same. In an optical illusion, your brain “tells” you that you see somethingthat is not present.

1. Examine the figure below. What do you see? Is a triangle present?

2. Examine the figure below. Do you think thelines could meet? Do they?

3. Examine the figure below. Which horizontalline appears longer? Measure the lines with aruler.

4. Stare at the number 1 in the figure below for atleast one minute. What happens to corner 1when you gaze at it steadily?

5. Examine the figures below. What do you see? When you look asecond time, do you see anything different? Can you see both

things at the same time?

6. Name some jobs people have in which they must be aware ofoptical illusions.

NAME DATE CLASS

Chapter 22

SKILL ASSESSMENT Optical Illusions

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Assessment Extending ContentExtending Content

Accessibility

Multicultural ConnectionsTest Practice WorkbookAssessment


I. Testing ConceptsMatch the description in the first column with the item in the second column by writing the correct letter in the spaceprovided. Some items in the second column may not be used.

_____ 1. conducts messages to neuron cell body 1/22:1

_____ 2. conducts messages away from neuron cell body 1/22:1

_____ 3. consists of the brain and a spinal cord 2/22:1

_____ 4. made up of nerves that connect the brain and spinal cord to other parts of body 2/22:1

_____ 5. brain part coordinating involuntary muscles 2/22:1

_____ 6. involuntary, automatic response to a stimulus 2/22:1

_____ 7. eye tissue composed of rods and cones 5/22:2

_____ 8. fluid-filled structure in inner ear shaped like a snail’s shell 5/22:2

_____ 9. control activities in the body; move through the bloodstream 7/22:3

For each of the following, write the letter of the term or phrase that best completes each sentence.

_____ 10. ________ conduct impulses from the brain to muscles or glands throughout the body.a. Interneurons b. Motor neurons c. Sensory neurons d. Synapses 1/22:1

_____ 11. The large part of the brain divided into two sections is the ________. 2/22:1a. cerebellum b. cerebrum c. midbrain d. pons

_____ 12. The spinal cord is an extension of the ________. 2/22:1a. brain stem b. cerebellum c. cerebrum d. spinal disk

_____ 13. The releasing of saliva is an example of the ________ at work. 2/22:1a. autonomic nervous system c. cerebrumb. cerebellum d. somatic nervous system

_____ 14. Reflex responses are controlled in your ________. 2/22:1a. cerebellum b. cerebrum c. midbrain d. spinal cord

_____ 15. In vision, light rays first pass through the ________. 4/22:2a. cornea b. lens c. optic nerve d. retina

_____ 16. The ________ controls your sense of balance. 5/22:2a. anvil b. hammer c. middle ear d. inner ear

_____ 17. Olfactory cells aid in the sense of ________. 5/22:2a. hearing b. smell c. touch d. vision

NAME DATE CLASS

Chapter 22

CHAPTER TESTThe Nervous and Endocrine Systems

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b. brain stem

c. central nervous system

d. cerebrum

e. cochlea

f. dendrite

g. hormones

h. motor neurons

i. olfactory cells

j. peripheral nervous system

k. reflex

l. retina

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In medical school, Alexa Canady fell in lovewith the nervous system because “it’s so neatand logical and precise.” She set her sights onbecoming a neurosurgeon and was the firstAfrican American woman in the United States tobecome one. Canady is now the chief neurosur-geon at Children’s Hospital of Michigan inDetroit. She is also an associate professor atWayne State University. Canady specializes inneurosurgery for children—an extremely chal-lenging field.

Delicate TissueThe human brain and nervous system are very

complex, and their health problems are varied.Some patients treated by neurosurgeons havehad brain injuries. These can occur because ofsuch things as an injury during birth, falls, orbike or car accidents. Other patients have dis-eases of the nervous system, such as epilepsy orcancer. Any problem that affects the brain isserious, because the brain controls the functionsof the rest of the body.

HydrocephalusOne condition that Canady treats is called

hydrocephalus. This condition occurs in infants.

Fluid accumulates in the brain, causing the brainand head to become enlarged. As the amount offluid increases, pressure increases inside theskull, pressing down on the delicate brain tissue.If you have ever caught your finger in a drawer,you have seen the damage that pressure can doto tissues. Bruises are a sign of broken bloodvessels and cells. In the brain, pressure canbreak blood vessels and destroy nerves andbrain cells. If a nerve is damaged, it can nolonger function. That means either that a mes-sage from the body may never reach the brain orthat a message from the brain to the body maynever be sent. In severe cases, high pressure inthe brain can result in death.

Canady is involved in research about the causefor hydrocephalus, but so far the answer hasbeen difficult to find. Treatment is possible,however. During the procedure, Canady insertsa tube into a specific area of the brain. The otherend of the tube extends down the neck and intothe abdomen. There, the fluid drains and iseliminated from the body, relieving the pressureand preventing further injury.

Injuries and TumorsCanady also studies and treats brain injuries

and tumors in children. Both of these can alsodamage brain cells and neurons through pres-sure on the brain. Tumors are enlarged massesof tissue resulting from uncontrolled cell divi-sion. Some tumors are cancerous, or malignant.Others are benign. Benign tumors grow moreslowly, do not affect surrounding tissues, and donot spread to other parts of the body. They usu-ally do not grow back after removal. In thebrain, however, benign tumors can be very dan-gerous. Brain injuries are more localized thanthe damage from hydrocephalus. What makesthe conditions so serious is the fact that they cansever nerves. The body cannot grow new braincells or neurons, and broken neurons do notheal. The damage is permanent. However, inminor injuries, the brain can often “reprogram”itself so that other parts of the brain can takeover for the cells that are lost. Intensive physicaltherapy can teach new skills to uninjured partsof the brain.

Tools for HealingTechnology has provided Canady with many

marvelous tools. Special X rays and imaging

Chapter 22

MULTICULTURAL CONNECTIONS

NAME DATE CLASS

Alexa Canady,Neurosurgeon

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Meeting Different Ability Levels

Transparencies

Chapter 20 Chapter 20 Nervous and Endocrine Systems

Enrichment WorksheetsReinforcementStudy Guide

for Content Mastery

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CHAPTER 22 Study Guide for Content Mastery

Overview The Nervous and Endocrine SystemsDirections: Use the following terms to complete the concept map below:

brain brain stem cerebellum cerebrum

Central nervoussystem

is made up of

contains

brainspinal cord

coordinatesvoluntarymuscles

interprets sensesand storesmemory

coordinatesinvoluntary

muscles

which which which

cerebellumcerebrum brain stem

BASIC

neuron

dendrite

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axon


NAME DATE CLASS

Chapter 22

REINFORCEMENT The Nervous System

Use with Section 1

Define each term and then label the figure below.

neuron 1. ______________________________________________________________________

dendrite 2. ______________________________________________________________________

axon 3. ______________________________________________________________________

synapse 4. ______________________________________________________________________

Name the three kinds of neurons and describe the function of each.

9. ____________________________________________________________________________________

10. ____________________________________________________________________________________

11. ____________________________________________________________________________________

Make a simple drawing of the brain and label its three main parts.

the nerve cell or the working unit of the nervous system

the branch of the neuron cell body that receives messages and

sends them to the cell body

the branch of the neuron that sends messages from the cell body

to the next neuron

the small space between one neuron and the next

Sensory neurons pick up information from receptors and send messages to

the brain.

Motor neurons conduct messages from the brain to the muscles and glands.

Interneurons are nerve cells throughout the brain and spinal cord that transmit

impulses from the sensory neurons to the motor neurons.

5.

6. 7.

8.

AT LEVELCopyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 59

The Nervous System

Use with Section 1

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Chapter 22

ENRICHMENT

Materialswad of paperglass door or window

Procedure1. Wad up a piece of paper into a ball. Stand

in front of a friend or relative and gentlytoss the paper ball at his or her face.Observe their eyelids as you throw thepaper.

2. Have your partner stand behind a glassdoor or window and again throw thepaper ball at the person. Observe the per-son’s eyelids as you throw the paper at theglass.

Conclude and Apply1. What was the response of your partner in step 1?_________________________________________

2. Was there a reason for the response? ____________________________________________________

3. What was the response of your partner in step 2?_________________________________________

4. Was there a reason for the response? ____________________________________________________

from harm

5. Since there was no logical way that the paper could hurt the person, what explains the reaction?

Blinking is a reflex action.

6. From the information in the textbook, what do you suppose the nerve pathway was during

this reaction? ________________________________________________________________________

then to the motor neurons that control the muscles of the eyelids.

The Eyes Have It

The person blinked.

The person blinked.

yes, to protect the eyes from harm

no, because the glass is there to protect the eyes

A nerve impulse went directly to an interneuron in the spinal cord and

CHALLENGE

Meeting Different Ability Levels

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Teaching TransparenciesScience Integration

Transparencies

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55

MESSAGE CENTERHow often do you speak with your friends on the telephone? The tele-

phone provides people with a way to communicate with others over bothshort and long distances. Your body also has a communication system. Thissystem allows different parts of your body to interact with each other. It alsoallows you to respond to changes that take place outside your body.

1. What are some ways in which people communicate with each other?

2. Why is communication important?

3. Why is it important for different parts of your body to communicate witheach other? What body system is responsible for carrying out this task?

SECTION FOCUS TRANSPARENCYSection 20-1

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EXTENDING THE SENSESPeople use many tools and instruments that help to extend their senses. For

example, some people with hearing impairments wear hearing aids thatamplify sounds, or make them louder. Scientists also use many tools andinstruments to help extend their senses. Some of these tools are shownbelow. Perhaps you’ve used some of these tools in your study of science orin other activities.

1. Which of the tools or instruments shown have you used?

2. What sense do the tools and instruments extend?

3. How do the tools and instruments shown magnify objects? Why is thisuseful?


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LIVING WITH DIABETESDiabetes is a disease of the endocrine system. It results when the pancreas

does not produce insulin in proper amounts. Insulin is a hormone thatenables the cells of the body to take in sugar in the form of glucose. If notenough insulin is produced by the pancreas, sugar accumulates in thebloodstream or is excreted from the body in urine.

1. Why would a person with diabetes need to take insulin in pills or byinjection?

2. Why is maintaining a healthful diet important to a diabetic?

3. Why is it important for a diabetic to get exercise regularly?


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Transparencies

This is a representation of key blackline masters available in the Teacher Classroom Resources.See Resource Manager boxes within the chapter for additional information.

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544C CHAPTER 20 NERVOUS AND ENDOCRINE SYSTEMS

Disturbancesof EndocrineFunction(Section 20-3)

Disturbances in func-tion of endocrine pro-duction may be classedas either hyperfunction, which refers to excess ac-tivity, or hypofunction, which means insufficientactivity. Hyperfunction of the anterior pituitarygland with overproduction of the growth hor-mone may result in gigantism. When excessadrenal-stimulating hormone is produced by anoveractive anterior pituitary gland, a group ofsymptoms known as Cushing’s disease occurs.Symptoms of Cushing’s disease include hyper-tension, weakness, plethora, bruising, and anunusual type of obesity. Deficiency in anteriorpituitary activity that takes place early in lifeleads to dwarfism, sexual underdevelopment,weakness, and occasionally severe gauntness.

Hormone-Producing Bacteria (Section 20-3)

Researchers have developed techniques forusing genetically altered bacteria to produce in-sulin for diabetic patients. This procedure isoften referred to as recombinant DNA technol-ogy, gene splicing, or genetic engineering. Thisallows insulin to now be produced in quantity.

A complex arrangement of light-sensitivecells within the retina of the eye reacts to lightenergy with wavelengths between 380 and 760millimicrons. The brain interprets the impulsesfrom the optic nerve.

The body’s sense of motion and equilibriumstructures are located within the inner ear. Sen-sory hair cells respond to movements of liquidsand of the tiny bits of calcium carbonate calledotoliths in the labyrinth canals.

The Pituitary Gland (Section 20-3)

The secretions of the pituitary gland are a goodexample of endocrine function. Its hormonesproduce a variety of actions and reactions. Thepituitary gland has three parts; the anterior lobe;the intermediate lobe, which is generallythought to be nonfunctional; and the posteriorlobe. The anterior lobe is considered the mastergland of the endocrine system. It produces sixhormones that cause stimulation of the growth ofbody cells, production of milk after birth, regula-tion of thyroid gland secretions, regulation ofadrenal cortex secretions, stimulation of egg andsperm production, and regulations of egg release.

The posterior lobe of the pituitary gland has arole in regulation of water secretion by the kid-neys, the contraction of the muscles of the uterusin the birth process, and the contraction of milk-producing glands in female breasts.

544F

For current events or science in the news,access the Glencoe Science Web Site atwww.glencoe.com/sec/science/ca

ontent Background

ontentBackground

CC

Teacher to TeacherTeacher to Teacher“To illustrate impulse pathways, students take turns representing

various parts of a nerve impulse pathway. They stand next to

each other in the correct order and pass a message along the

pathway. The ‘interneuron’ student reads the message and de-

cides whether the response is muscular or glandular.”

Rebecca S. Buckingham, Teacher

Lisbon Central School

Lisbon, NY

Chapter 20

544E CHAPTER 20 THE NERVOUS AND ENDOCRINE SYSTEMS

Receptor Cells (Section 20-1)

Specialized receptor cells respond to specific stim-uli from various parts of the body. The stimulusproduces a self-propagating wave of negativecharges that are transmitted to the central nervoussystem via peripheral nerves. The nerve impulsetravels at a rate of approximately 120 m/s. Thebrain and spinal cord of the central nervous sys-tem interpret the stimuli information.

Appropriate responses are sent via nerves tovarious body parts, which react to the stimulus.The response is a coordinated, integrated actionthat maintains homeostasis within the body.

Sensory Receptors (Section 20-2)

Sensory receptors of the body respond to envi-ronmental changes. Voluntary movement ofhead, limbs, and body is caused by nerve im-pulses arising in the motor area of the brain andcarried by nerves to connect with skeletal mus-cles. The reaction involves both excitation ofnerve cells stimulating the muscles involvedand inhibition of the cells that stimulate oppos-ing muscles.

Movements also may occur in direct responseto outside stimuli and are called reflexes. Theseclasses of receptors constantly send impulsesinto the central nervous system. Some receptorsare sensitive to pain, temperature, touch, andpressure. Others react to changes in the internalenvironment, and a third type responds to

variations in movement, position, and tension.These impulses end in special areas of the brain,as do those of special receptors concerned withsight, hearing, smell, and taste.

Olfactory receptors, primarily in the nose, re-spond to gas molecules that become dissolvedin the watery fluids of the nasal passages.

Taste buds located on small projections calledpapillae of the tongue, the soft palate, and thewalls of the pharynx are sensitive to substancesdissolved in liquids. Specialized taste cellswithin the taste buds function as receptors.

Auditory sensory organs are present in theears. Vibrations in the air with frequencies be-tween about 16 000 and 20 000 cycles per sec-ond can be detected as a sound by the ear. Hair-like projections of the organ of Corti within theinner ear respond to the vibrations and transmitnerve impulses to the brain.

Products Available from GlencoeTo order the following products for use with this chap-ter, call Glencoe at 1-800-334-7344:

CD-ROMNGS PictureShow: Human Body 1Curriculum KitGeoKit: Human Body 2Transparency SetNGS PicturePack: Human Body 1VideodiscSTV: Human Body

Products Available from NationalGeographic SocietyTo order the following products for use with this chapter,call National Geographic Society at 1-800-368-2728:

VideosNervous System (The Human Body Series)Incredible Human Machine

Teacher’s Corner

Chapter 20 The Nervous and Endocrine Systems

CD-ROMGlencoe Science Voyages Interactive CD-ROM

Chapter SummariesUse the Chapter Summary to introduce, teach,or review chapter material.

Helping You Prepare

http://www.glencoe.com/sec/science/ca

1. Look at the figure at the right ofthe page.

2. Estimate the difference in heightsbetween pole A and pole C.

3. Use a metric ruler to measure theheights of poles A, B, and C.

Explore Activity

Who’s in front of you? What note do we start on? Where’sthe conductor? Am I marching in rhythm? There’s a lot

to be aware of when you’re part of a marching band. You mustbe sensitive to your surroundings and aware when changestake place. All organisms must be able to detect what is hap-pening around them. Sights or sounds can warn of danger.Odors can help find food. Sensations of hot and cold can protectfrom fire or extreme tempera-tures. In this chapter, you willlearn how your body’s nervoussystem interprets all of the sen-sations it receives to produce apicture of its surroundings. Inthe following activity, find outwhether your eyes can inter-pret objects correctly.

Observe Objects

In your Science Journal,record what you foundout about the height ofthe lines. Were yourestimates correct? Whatdid your eyes tell you?

545

AB

C

545

Explore ActivityPurpose

Visual-Spatial Use theExplore Activity to intro-

duce students to one aspect ofthe nervous system—vision.Inform students that they willbe learning more about thenervous and endocrine sys-tems as they read the chapter.

PreparationCollect some additional il-

lustrations of optical illu-sions, such as inkblot tests,to extend the learning of thisactivity.

Materialsmetric ruler

Teaching StrategiesHave students devise their

own optical illusions in theform of inkblots.

S t u d e n t ss h o u l d o b s e r v e

that the heights are the samebut appear to be different.They should also include areference as to whether theirestimates were correct.

Performance Have stu-dents collect other optical il-lusions and work in smallgroups to find how the eyescan be tricked. Have thempresent their findings on aposter. Use Performance As-sessment in the ScienceClassroom, p. 73.

ELLL2

Assessment

PortfolioRefer to p. 567 for suggested items that stu-dents might select for their portfolios.Performance AssessmentSee p. 567 for additional Performance As-sessment options.Skill Builder, pp. 552, 564MiniLab, pp. 555, 558Activity 20-1, p. 553; 20-2, pp. 560–561

Content AssessmentSection Assessment, pp. 552, 559, 564Chapter Assessment, pp. 568–569Proficiency Prep, pp. 552, 559, 564

Assessment Planner

CHAPTER 20The Nervous

and EndocrineSystems

The Nervous and Endocrine

Systems

Chapter Preview

Section 20-1The NervousSystem

Section 20-2The Senses

Section 20-3The EndocrineSystem

Skills Preview

Skill Builders• Map Concepts

• Make and Use a Table

Activities• Compare and Contrast

• Design an Experiment

MiniLabs • Interpret Data

The Nervousand EndocrineSystems

The Nervousand EndocrineSystems

✔Reading Check

20

Before beginning Section 20-1,

make a chart that will allow

you to compare and contrast

the central nervous system

and the peripheral nervous

system. Fill it in as you read.

C H A P T E R

544

544 CHAPTER 20 THE NERVOUS AND ENDOCRINE SYSTEMS

CHAPTER OVERVIEWSection 20-1 This sectioncenters on the functions of thenervous system, the move-ment of impulses along neu-rons, and the two major divi-sions of the system.Section 20-2 This section de-scribes the sense organs andhow they enable the body todistinguish changes in its inter-nal and external environments.Section 20-3 The endocrinesystem and its secretions arestudied in this section. The ef-fects of the hormones on tis-sues are described.

Chapter Vocabularyneuron cerebrumdendrite cerebellumaxon brain stemsynapse reflexcentral cochleanervous retinasystem olfactory cell

peripheral taste budnervous hormonesystem target tissue

Theme ConnectionStability and Change The in-tegrated efforts of the nervousand endocrine systems bringabout a stable environmentnecessary for the healthyfunctioning of the body.

If time does not permit

teaching the entire chap-

ter, use Reviewing Main

Ideas on pp. 566-567.

OUT OF

TIME? MultipleLearning

Styles

Look for the following logos for strategies that emphasize different learning modalities.

Linguistic Science Journal, pp. 547,558; Across the Curriculum, p. 548;

Assessment, pp. 559, 564; Preview, p. 566Logical-Mathematical Activity, p.553; Assessment, p. 553Visual-Spatial Explore Activity, p. 545;Activity, pp. 547, 563; Visual Learning,

p. 547; Reteach, pp. 551, 557, 563, 566Auditory-Musical Out of Time, p. 566

Kinesthetic Quick Demo, p. 548;Making a Model, p. 549; Multiple

Learning Styles, p. 549; MiniLab, pp. 555, 558Interpersonal Discussion, pp. 550,551; Enrichment, p. 550; Tying to Pre-

vious Knowledge, p. 554; Activity pp.560–561; Review, p. 566

Intrapersonal Enrichment, p. 548

20-1 THE NERVOUS SYSTEM 547

2 TeachActivity

Visual-Spatial In a school yard or athletic

field, position two students100 m apart. Use this visualrepresentation to illustratethe distance that some nerveimpulses travel in 1 s.

DiscussionWhat would happen if

all your sensory neuronsstopped working? Your brainwould stop receiving stimulifrom inside and outside yourbody, making it impossible tomaintain homeostasis.

Teacher FYIThe axons of neurons grow

and branch when used. Moreand better connections withother neurons result in learn-ing. Schoolwork helps neu-rons make connections.

Caption AnswerFigure 20-1 Each neuron canreceive impulses from severaldifferent sensory receptors be-cause of the increased number ofdendrites.

COOP LEARN

ELLL2

Figure 20-2 Have students follow thesequence of events that occurs as an im-pulse is initiated and moves through thebody, and a response is generated.

LearningVISUAL

Nerve Analogy Have students write aparagraph that explains how a nerve issimilar to a wire going from a controllingswitch (stimulus) to a lightbulb (re-sponse). PL2

20 1 THE NERVOUS SYSTEM 547

NeuronsThe working unit of the nervous system is the nerve

cell, or neuron (NOO rahn). The single neuron inFigure 20-1 is made up of a cell body and branchescalled dendrites and axons. Dendrites receive messagesand send them to the cell body. An axon (AK sahn) car-ries messages away from the cell body. Any messagecarried by a neuron is called an impulse. Notice that theend of the axon branches. This allows the impulses tomove to many other muscles, neurons, or glands.

Types of NeuronsYour skin and other sense organs are equipped with struc-

tures called receptors that respond to various stimuli. Threetypes of neurons—sensory neurons, motor neurons, andinterneurons—then become involved with transportingimpulses about the stimuli. As illustrated in Figure 20-2,sensory neurons (B) receive information and send impulsesto the brain or spinal cord. Once the impulses reach yourbrain or spinal cord, interneurons relay the impulses from thesensory to motor neurons. You have more interneurons inyour body than either of the other two types of neurons.Motor neurons (D) then conduct impulses from the brain orspinal cord to muscles or glands throughout your body.

D The response issent back alongmotor neuronsto your muscles.

C Your brain sortsthe informationand determinesa response.

E Your heart immediatelystarts to pound and yourbreathing rate increases.You throw the book.

Figure 20-2 In your nervoussystem, impulses travel a pathway.Together, the three types of neu-rons act like a relay team, movingimpulses through your body fromstimulus to response.

A When you hear the lampbreak, sensory receptors inyour ears are stimulated.

B A message is sent to yourbrain by way of sensoryneurons.

46: 5a, 5bPage 547: 5a, 5b

CA Science ContentStandards


546 CHAPTER 20 THE NERVOUS AN EN OCRINE SYSTEMS

The basic structure of a neuronand how an impulse movesInformation about the centraland peripheral nervous systemsHow drugs affect the body

Vocabularyneurondendriteaxonsynapsecentral nervous systemperipheral nervous systemcerebrumcerebellumbrain stemreflex

Your body can react to yourenvironment because of yournervous system.

Why What You'll Learn

It's Important

You'll Learn

It's Important It's Important


It's Important

You'll Learn

It's Important

You'll Learn

Figure 20-1 A neu-ron is made up of a cellbody, dendrites, and anaxon. How does thebranching of the dendritesallow for more impulses tobe picked up by the neu-ron?

Direction of impulse

Dendrites

Cell body

Axon

The NervousSystem

The Nervous System at WorkAfter doing the dishes and finishing your homework, you

settle down in your favorite chair and pick up that mysterynovel you’ve been trying to finish. Only three pages to go. . . Who did it? Why did she do it? Then, “CRASH!” Youscream and throw your book in the air. What made thatunearthly noise? You turn around to find that your dog’swagging tail just swept the lamp off the table beside you.Suddenly, you’re aware that your heart is racing and yourhands are shaking. But, then, after a few minutes, yourbreathing returns to normal and your heartbeat is back to itsregular rate. What’s going on?

Response to StimuliThe scene described above is an example of how your body

responds to changes in its environment and adjusts itself.Your body makes these adjustments with the help of yournervous system. Any change inside or outside your body thatbrings about a response is called a stimulus. Each day, you’rebombarded by thousands of stimuli. Noise, light, the smell offood, and the temperature of the air are all stimuli from out-side your body. A growling stomach is an example of aninternal stimulus.

How can your body handle all these stimuli? Your bodyhas internal control systems that maintain steady conditions,no matter what’s going on outside the body. This is calledhomeostasis. Breathing rate, heartbeat rate, and digestion arejust a few of the activities that are constantly checked and reg-ulated. Your nervous system and the endocrine system, achemical control system described later in this chapter, arethe main ways your body maintains homeostasis.

20 1Prepare

PreplanningRefer to the Chapter Orga-nizer on pp. 544A–B.

1 Motivate

Tying to PreviousKnowledge

Remind students that coor-dinated body movements areaccomplished by the nervoussystem and the skeletal mus-cles working together.

SECTION 20•1

Bellringer

Before presenting the lesson,display Section Focus Transparency 55 on the

overhead projector. Use the accompanying Focus Activityworksheet. ELLL2

Refer to Recep-tor Cells on p. 544E.

ontent Background

ontentBackground

CC

The following Teacher Classroom Resources can be used with Section 20-1:

Reproducible Masters

Activity Worksheets, pp. 109–110

Enrichment, p. 55

Laboratory Manual, pp. 117–120

Multicultural Connections, pp. 39–40

Reinforcement, p. 55

Study Guide, pp. 77-78

Transparencies

Teaching Transparency 39 L2

ELLL1

L2

L2

L2

L3

L2

Resource Manager

Copyright©Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

55

55

MESSAGE CENTER

How often do you speak with your friends on the telephone? The tele-

phone provides people with a way to communicate with others over both

short and long distances. Your body also has a communication system. This

system allows different parts of your body to interact with each other. It also

allows you to respond to changes that take place outside your body.

1. What are some ways in which people communicate with each other?

2. Why is communication important?

3. Why is it important for different parts of your body to communicate with

each other? What body system is responsible for carrying out this task?

SECTION FOCUS TRANSPARENCY

Section 20-1


Guided Reading Strategy

Quickwrites This strategy, sometimes called

freewrites, lets students use spontaneous

writing to discover what they already know.

Have students write a list of ideas about a

topic, then share these ideas with the class.

Next, have students write their ideas freely in

a paragraph without worrying about punctua-

tion, spelling, and grammar. Have students use

a Quickwrite to share ideas during or after a

learning experience in this chapter.

Making a ModelKinesthetic Have stu-dents make a model of

the vertebral column andspinal cord by stringing 31thread spools on a rope. Usecircular pieces of foam rubberfor the disks between the ver-tebrae. Have students notehow the cord (rope) is pro-tected.

Using Science WordsHave students compare the

use of the word cortex as usedby botanists and physiologists.L2

COOP LEARNELLL2

The adult humanbrain weighs about 1.4 kgand has a volume of ap-proximately 1500 cm3. Itcontains over 100 billionneurons.

ontent Background

ontentBackground

CC

Figure 20-5 Have stu-dents describe how thebrain is protected. Hair,skin, skull bones, andmembranes protect thebrain.

LearningVISUAL

The isotope fluorine-18 is used toprovide the radioactivity used inPET. In addition to detection ofsensory areas, PET has been usedto detect tumors in the brain.

Kinesthetic Have studentsmake a model of the brain from

papier-mâché or Styrofoam. Painteach part a different color and labelthe areas of activity. ELLL1

Multiple Learning Styles

INTEGRATIONPHYSICS

Watching the BrainScientists use positron emis-sion tomography (PET) tolearn more about the brain.Brain cells that are activetake up radioactive glucose,which causes an image toappear on a color monitor.Different colors indicatewhich areas of the brain arebeing stimulated. By com-paring different PET images,researchers have located theareas of the brain used forseeing, reading, hearing,speaking, and thinking.


The BrainThe brain is made up of approximately 100 billion neurons.

You can see in Figure 20-5 that the brain is divided into threemajor parts: cerebrum, cerebellum, and brain stem. Thelargest part of the brain, the cerebrum (suh REE brum), isdivided into two large sections called hemispheres. Here,impulses from the senses are interpreted, memory is stored,and the work of voluntary muscles is controlled. The outerlayer of the cerebrum, the cortex, is marked by many ridgesand grooves. The diagram also shows some of the tasks thatsections of the cortex control.

A second part of the brain, the cerebellum (ser uh BEL um),is behind and under the cerebrum. It coordinates voluntarymuscle movements and maintains balance and muscle tone.

The brain stem extends from the cerebrum and connects thebrain to the spinal cord. It is made up of the midbrain, thepons, and the medulla. The brain stem controls your heart-beat, breathing, and blood pressure by coordinating the in-voluntary muscle movements of these functions.

The Spinal CordYour spinal cord is an extension of the brain stem. It is made

up of bundles of neurons that carry impulses from all parts ofthe body to the brain and from the brain to all parts of yourbody. The spinal cord, illustrated in Figure 20-4, is about asbig around as an adult thumb and it is about 43 cm long.

Cerebrum

SensoryMotor Tongue

Chewing

Swallowing

Smell

Brain StemCerebellum

Hearing

Vision

Salivation

Figure 20-5 Differentareas of the brain controlspecific body activities.

Page 548: 5a, 5bPage 549: 5a, 5b


SynapseNeurons don’t touch each other. How does an impulse

move from one neuron to another? To get from one neuron tothe next, an impulse moves across a small space called asynapse (SIHN aps). In Figure 20-3, you can see that when animpulse reaches the end of an axon, a chemical is released bythe axon. This chemical diffuses across the synapse and startsan impulse in the dendrite or cell body of the next neuron. Inthis way, an impulse moves from one neuron to another.

The Central Nervous SystemFigure 20-4 shows how organs of the nervous system are

grouped into two major divisions: the central nervous system(CNS) and the peripheral nervous system (PNS). The centralnervous system is made up of the brain and spinal cord. Theperipheral (puh RIHF rul) nervous system is made up of allthe nerves outside the CNS, including cranial nerves andspinal nerves. These nerves connect the brain and spinal cord

to other body parts.The brain coordinates all

your body activities. If some-one pokes you in the ribs,your whole body reacts. Yourneurons are adapted in sucha way that impulses move inonly one direction. Sensoryneurons send impulses thatmove from a receptor to thebrain or spinal cord.

Axon

Synapse

Axon

ChemicalSurface of

next neuron

Direction of impulse

BrainSpinalcord

(CNS)

Spinalnerves(PNS)

Dendrite


Spinal nerve

Spinal cord

Spinal cord

Cerebellum

SkullBrain

Cerebrum

Vertebra

Figure 20-3 An impulsemoves in only one directionacross a synapse—from anaxon to the dendrites or cellbody of another neuron.

Figure 20-4 The brain andspinal cord (yellow) form thecentral nervous system, whichsorts and interprets informationfrom stimuli. All other nervesare part of the peripheral ner-vous system (green).


EnrichmentIntrapersonal Havestudents research and

report to the rest of the classon concussions. They shouldfind out how they occur, whathappens to the brain, symp-toms, and treatment. Preven-tive measures such as wear-ing seat belts should also bebrought out.

Use the Flex Your Brain activity to have students explore SYNAPSES.

Flex Your BrainFlex Your Brain

Language Arts Have students look upsynapse in the dictionary. Students will findthat it comes from the Greek roots syn (to-gether) and haptein (unite). Ask students tothink about how the roots of the word reflectits meaning. L2

Across the CurriculumAcross the Curriculum

VideodiscThe Infinite Voyage: Unseen WorldsChapter 7 Brain TumorSurgery: Made Possible by MRI2:30Refer to the Teacher Guide forbar codes and teaching strategies.

Quick DemoKinesthetic Have threestudents stand side by

side. Their arms and fingersshould be outstretched attheir sides. Starting at oneend of the line, have the stu-dents pass a metric ruler fromperson to person. Students’fingers should not touch. Usethis to show students how animpulse travels from a sen-sory neuron through an interneuron to a motor neu-ron. Have students identifythe axon and dendrites ofeach “nerve cell.” COOP LEARN

ELLL2


3 AssessCheck for UnderstandingDiscussion

Interpersonal Havestudents discuss the

purpose of the extensive fold-ing of the surface of the cere-brum. The folding provides agreater surface area to be con-tained within the enclosure ofthe skull. Why might a hardblow to the back of the headcause a vision disorder? Theprimary visual area of the brainis located at the lower rear side ofthe cerebrum.

ReteachVisual-Spatial Havestudents make flash

cards with the names of themajor parts of the nervoussystem. Use the back of thecard to write a brief descrip-tion of the function. Studentscan use the cards to quiz eachother to review section con-tent.

ExtensionFor students who have

mastered this section, use theReinforcement and Enrich-ment masters.

COOP LEARNL1

History In the latter part of the eigh-teenth century, scientists had an interest inanimals that were able to produce an electricshock, such as the electric eel. These investi-gations led to research on the effects of elec-tricity on nerves and the muscular contrac-tions that could be produced.


Alzheimer’s disease is the resultof the failure of nerve cells in the brain tocommunicate. Alzheimer’s patients haveinsufficient amounts of acetylcholine, achemical that carries impulses from onenerve to the next.

ontent Background

ontent Background

CC


ReflexesHave you ever moved quickly from something hot or

sharp? Then you’ve experienced a reflex. A reflex is an in-voluntary and automatic response to a stimulus. Usually, youcan’t control reflexes because they occur before you knowwhat has happened. A reflex involves a simple nerve path-way called a reflex arc. Figure 20-7 shows a reflex arc. As youreach for the pizza, some hot cheese falls on your finger.Sensory receptors in your finger respond to the hot cheese,and an impulse is sent to the spinal cord. The impulse passesto an interneuron in the spinal cord that immediately relaysthe impulse to motor neurons. Motor neurons transmit theimpulse to muscles in your arm. Instantly, without thinking,you pull your arm back in response to the burning food. Thisis a withdrawal reflex. A reflex allows the body to respondwithout having to think about what action to take. Reflexresponses are controlled in your spinal cord, not in yourbrain. Your brain acts after the reflex to help you figure outwhat to do to make the pain stop.

Remember in Figure 20-2 how the girl was frightened afterthe lamp was broken? What would have happened if herbreathing and heartbeat rate didn’t calm down within a fewminutes? Your body system can’t be kept in a state of contin-ual excitement. The organs of your nervous system controland coordinate responses to maintain homeostasis withinyour body.

✔

Interneuron

Sensory neuron

Direction ofimpulse

Receptor in skin

Motor neuron

Spinal cord

Muscle contracts

Figure 20-7 Your response ina reflex is controlled in your spinalcord, not in your brain.

✔Reading Check

Why are reflexes

important?

Visit the GlencoeScience Web Site atwww.glencoe.com/sec/science/ca formore information aboutthe nervous system.

A Reflex Arc

ISUALIZINGV

ISUALIZING

G

V ISUALIZINGV

Answer to

Reading Check ✔

Reflexes allow quick reactions

to dangerous situations with-

out having to think about

what to do.

Visual LearningFigure 20-7 Have studentsdescribe the movement of im-pulses in the diagram.

Page 550: 5a, 5b, 7aPage 551: 5a, 5b, 7b


Answer to Text Question

What purpose might thisfluid serve? It cushions thevertebrae.

Caption AnswerFigure 20-6 the autonomicsystem

DiscussionInterpersonal Havestudents discuss other

reflex responses to stimulithat prevent injury to thebody. Examples include: eye-lid closing when there ismovement near the eye, rapidupward foot movement whenstepping on a sharp object.

Estimates will vary. Possibleanswers could be from 80 cmto 1 m. Length of time fortravel will vary from 0.0067 sto 0.0083 s.

Correcting Misconceptions

Alcohol is often perceivedas a stimulant because it ini-tially makes the person feelmore energetic. However, al-cohol actually slows downthe actions of the central ner-vous system.

EnrichmentInterpersonal Havestudents find out which

motor reflexes a child is bornwith. As part of their re-search, they could interview apediatrician.


The CNS is protected by a bony cap called the skull, by verte-brae, and by three layers of membranes. Between some ofthese membranes is a fluid called cerebrospinal (suh ree brohSPINE ul) fluid. What purpose might this fluid serve?

The Peripheral Nervous SystemYour brain and spinal cord are connected to the rest of your

body by the peripheral nervous system. The PNS is made upof 12 pairs of cranial nerves from your brain and 31 pairs ofspinal nerves from your spinal cord. These nerves link yourcentral nervous system with all parts of your body. Spinalnerves are made up of bundles of sensory and motor neu-rons. For this reason, a single spinal nerve may have impulsesgoing to and from the brain at the same time.

The peripheral nervous system has two divisions. Thesomatic system consists of the cranial and spinal nerves thatgo from the central nervous system to your skeletal muscles.The second division, the autonomic system, controls yourheartbeat rate, breathing, digestion, and gland functions.When your salivary glands release saliva, your autonomicsystem is at work. Use Figure 20-6 to help you rememberthese two divisions.

Peripheral Nervous System(cranial and spinal nerves)

Somatic system

Skeletal muscles Heartbeat rate

Breathing, digestive,salivary glands

Autonomic system

One of the longestspinal nerves extendsfrom the spinal cordto muscles in the foot.Estimate the length ofthis nerve. If the rateof travel of a nervepulse is approximately120 m per second,what is the length oftime for an impulse totravel from the spinalcord to the foot?

Figure 20-6 The divisions ofthe peripheral nervous system areshown. What part of the PNScontrols your breathing whileyou sleep?

For Internet tips, see Glencoe’s Using the Internet in the Science Classroom.

Internet Addresses


Life Science Have students research behaviors that are not reflexes but are innatebehaviors in animals. Examples are nestbuilding by birds and web construction byspiders. Find out if humans have any innate behaviors.

Integrating the SciencesIntegrating the Sciences


Activity

20•1Using Scientific MethodsUsing Scientific Methods


Reaction TimeYour body responds quickly to some kinds of stimuli, and

reflexes allow you to react quickly without even thinking.Sometimes you can improve how quickly you react. Complete thisactivity to see if you can improve your reaction time.

Materials• Metric ruler

What You’ll InvestigateHow can reaction time be improved?

Goals• Observe reflexes.• Identify stimuli and responses.

Procedure1. Make a data table in your Science Journal to

record where the ruler is caught during thisactivity. Possible column heads are Trial, RightHand, and Left Hand.

2. Have a partner hold the ruler at the top end.3. Hold the thumb and finger of your right hand

apart at the bottom of the ruler. Do not touchthe ruler.

4. Your partner must let go of the ruler withoutwarning you.

5. Try to catch the ruler by bringing your thumband finger together quickly.

6. Repeat this activity several times and recordwhere the ruler was caught in a data table.

7. Repeat this activity with your left hand. Recordyour results.

Conclude and Apply1. Identify the stimulus in this activity.2. Identify the response in this activity.3. Identify the variable in this activity.4. Use the table on this page to find your reaction

time.5. What was your average reaction time for your

right hand? For your left hand?6. Compare the response of your writing hand

and your other hand for this activity.7. Draw a conclusion about how practice

relates to stimulus-response time.

Activity 20 1

Where Caught (cm) Reaction Time (s)

5 0.10 10 0.14 15 0.17 20 0.20 25 0.23 30 0.25

Reaction Time


Purpose

Logical-MathematicalStudents will observe reac-

tion time.

Process Skillsobserving, communicating, usingnumbers, recognizing and usingspatial relationships, measuring inSI, interpreting data

Time30 minutes

Materialsmetric ruler

Teaching StrategiesStudents should keep their

eyes on the ruler as the partner releases it.

Answers to Questions1. the ruler falling2. catching the ruler 3. which hand is used4. Answers will vary.5. To find the average, students

should add all reaction timesand divide by the number oftrials.

6. Answers will vary. Generally,the writing hand reacts faster.

7. With practice, stimulus re-sponse time will probably improve.

COOP LEARNELLL2

Performance To further assess students’ abili-ties to measure and improve reaction time, havethem formulate and test a hypothesis about howlong it would take the nonwriting hand to betrained to respond as the writing hand responds.Use Performance Assessment in the Sci-ence Classroom, p. 21.

AssessmentSample data for left-handed person

Where the Ruler Was Caught

Trial Right hand Left hand

1 30 20

2 20 10

3 15 10Page 552: 5a, 5b, 7bPage 553: 5a, 5b, 7a, 7c



4 CloseProficiency PrepUse this quiz to check stu-dents’ recall of section content.

1. What is the function ofthe dendrite? to receive themessages and send them tothe cell body

2. What are nerve cells thatrelay impulses from sen-sory to motor neurons?interneurons

3. The peripheral nervoussystem consists of whattwo types of nerves? cra-nial, spinal

4. What connects the brainto the spinal cord? thebrain stem

1. See Figure 20-1.2. The central nervous sys-

tem is made up of thebrain and spinal cord.The peripheral nervoussystem is made up of cra-nial and spinal nerves.

3. Sensory neurons receiveinformation and send im-pulses to the spinal cordor brain. Motor neuronsconduct impulses fromthe brain or spinal cord tomuscles or glands through-out the body.

4. Think Critically Cocoacontains caffeine, whichis a stimulant that cancause sleeplessness.

Section AssessmentSection Assessment

AssessmentPortfolio Haves students make models oftwo neurons. Have them clearly label thesynapse, axons, dendrites, cell bodies, andneurotransmitters. Use Performance As-sessment in the Science Classroom, p. 51.

5. Skill BuilderThe concept map should in-clude the following: stimu-

lus—sensory neurons—interneurons—motor neurons—response.

Flowcharts should show an impulse moving from receptor to sensory neuron to interneuron in the spinalcord to motor neuron to muscle in foot.


Drugs and the Nervous SystemMany drugs, such as alcohol and caffeine, have a direct

effect on your nervous system. When swallowed, alcoholpasses directly through the walls of the stomach and smallintestine into the circulatory system. Alcohol is classified as adepressant drug. A depressant slows down the activities ofthe central nervous system. Judgment, reasoning, memory,and concentration are impaired. Muscle functions also areaffected. Heavy use of alcohol destroys brain and liver cells.

Caffeine is a stimulant, a drug that speeds up the activity ofthe central nervous system. Too much caffeine can increase

heartbeat rate and cause restlessness, tremors, and insom-nia. It also can stimulate the kidneys to produce more

urine. Caffeine can cause physical dependence.When people stop taking caffeine, they can have

headaches and nausea. Caffeine is found in cof-fee, tea, cocoa, and many soft drinks, as seen

in Figure 20-8.Think again about a scare from the

loud noise. The organs of your ner-vous system control and coordinateresponses to maintain homeostasiswithin your body. This task is moredifficult when your body must copewith the effects of drugs.

1. Draw and label the parts of a neuron.2. Compare the central and peripheral nervous

systems.3. Compare sensory and motor neurons.4. Think Critically: During a cold winter

evening, you have several cups of hot cocoa.Explain why you have trouble falling asleep.

5. Skill BuilderConcept Mapping Prepare an

events chain concept map of the different kindsof neurons an impulse moves along from a stimulus to a response. If you need help, refer to Concept Mapping in the Skill Handbook onpage 678.


Word Processing Createa flowchart showing thereflex pathway of a nerveimpulse when you step on a sharp object. Labelthe body parts involved ineach step of the process. If you need help, refer topage 696.

Figure 20-8 Caffeine, asubstance found in cola, coffee,and other types of food anddrink, can cause excitability andsleeplessness.

20-2 THE SENSES 555

2 TeachTying to PreviousKnowledge

Interpersonal Havestudents compare the

sensory system of informa-tion processing with that of atelephone system. Have thembrainstorm similarities anddifferences.

Performance To further assess students’ under-standing of balance, have them repeat the activitywith feet apart or arms extended sideways. UsePerformance Assessment in the ScienceClassroom, p. 25.

Assessment

20 2 THE SENSES 555

Figure 20-10 shows that your ear isdivided into three sections: the outer, mid-dle, and inner ear. Your outer ear trapssound waves and funnels them down theear canal to the middle ear. The soundwaves cause the eardrum to vibrate muchlike the membrane on a drum. These vibra-tions then move through three little bonescalled the hammer, anvil, and stirrup. Thestirrup bone rests against a second mem-brane on an opening to the inner ear.

The Inner EarThe cochlea (KOH klee uh) is a fluid-

filled structure shaped like a snail’s shell,in the inner ear. When the stirrup vibrates,fluids in the cochlea also begin to vibrate.These vibrations stimulate nerve endingsin the cochlea, and impulses are sent to thebrain by the auditory nerve. Depending onhow the nerve endings are stimulated, youhear a different type of sound. High-pitched sounds make the endings movedifferently than lower, deeper sounds.

Balance also is controlled in the inner ear.Special structures and fluids in the innerear constantly adjust to the position of your head. This stimulates impulses tothe brain, which interprets the impulsesand helps you make the necessary adjust-ments to maintain your balance.

Outer ear

EardrumHammer

Anvil

Stirrup

Cochlea(Hearing)

Semicircularcanals (Balance)

Middle earInner ear

Figure 20-10 Your ear respondsto sound waves and to changes in theposition of your head. Why does spin-ning around make you dizzy?

Observing Balance Control

Procedure

1. Place two narrow strips of paper on the wall toform two parallel vertical lines. Have a studentstand between them, as still and straight aspossible without leaning on the wall, for threeminutes.

2. Observe how well balance is maintained.3. Have the student close his or her eyes and

repeat standing within the lines for three minutes.

Analysis

1. When was balance more difficult to maintain?Why?

2. What other factors might cause a person tolose the sense of balance?

For additional help doing thisactivity at home, see the corre-sponding pages in the Home In-volvement booklet.

Purpose

Kinesthetic Students willobserve and make infer-

ences concerning the factors thataffect their ability to maintain bal-ance.

Materialstwo narrow strips of paper, mask-ing tape

Teaching StrategiesHave students perform this ac-

tivity with another family member.Have them take turns standingand observing. Record whetherthe person standing tends to leanmore to one side or the other.Safety Precautions Some per-sons may become disoriented. Beprepared to help any person wholooks as if he or she might fall.

Analysis1. When the eyes are closed;

when the eyes are open, aperson can focus on a point tohelp the body remain bal-anced.

2. Answers will vary but couldinclude such conditions as aninner ear infection or loud,continuous noise.

ELLL2

Caption AnswerFigure 20-10 Spinning makes the fluids in theinner ear send impulses to the brain that conflictwith the actual position of the head. Dizzinessresults.

The SensesIn Touch with Your Environment

Science fiction stories about space often describe energyforce fields around spaceships. When some form of energytries to enter the ship’s force field, the ship is put on alert.Your body has an alert system as well, in the form of senseorgans. Your senses enable you to see, hear, smell, taste,touch, and feel whatever comes into your personal territory.The energy that stimulates your sense organs may be in theform of light rays, heat, sound waves, chemicals, or pressure.Sense organs are adapted for capturing and transmittingthese different forms of energy.

HearingSound energy is to hearing as light energy is to vision. As

illustrated in Figure 20-9, when an object vibrates, it causesthe air around it to vibrate, thus producing energy in the formof sound waves. When sound waves reach your ears, theystimulate nerve cells deep in your ear. Impulses are sent tothe brain. The brain responds, and you hear a sound.


20 2

The sensory receptors ineach sense organWhat type of stimulus eachsense organ responds to and howWhy healthy senses areneeded

Vocabularycochlea olfactory cellretina taste bud

Your senses make you awareof your environment, whichhelps keep you safe.


It's Important

You'll Learn



It's Important

You'll Learn

It's Important

You'll Learn

Figure 20-9 A vibrating objectproduces sound waves that are heardby your ears.

A When the ruler vibratesupward or downward, itpushes the particles of airin front of its movementcloser together.

C As the ruler vibrates upand down, it creates awave-pattern of alternat-ing particles of air thatare compressed andspread out. This waveof sound travels to youreardrum, where thesound is received.

Sound waves

B At the same time, the airparticles on the oppositeside of the ruler spread farther apart.


Prepare


1 Motivate

SECTION 20•2

Bellringer



Refer to SensoryReceptors on pp. 544E–F.

ontent Background

ontent Background

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Reproducible MastersActivity Worksheets, pp. 111–114 Enrichment, p. 56 Home Involvement, p. 28 Laboratory Manual, pp. 121–124


Transparencies

Science Integration Transparency 20 L2

L2

L2

L2

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Resource Manager

Copyright©Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

56

56

EXTENDING THE SENSES

People use many tools and instruments that help to extend their senses. For

example, some people with hearing impairments wear hearing aids that

amplify sounds, or make them louder. Scientists also use many tools and

instruments to help extend their senses. Some of these tools are shown

below. Perhaps you’ve used some of these tools in your study of science or

in other activities.

1. Which of the tools or instruments shown have you used?

2. What sense do the tools and instruments extend?

3. How do the tools and instruments shown magnify objects? Why is this

useful?


Section 20-2

Page 554: 5a, 5b, 5gPage 555: 5a, 5b, 7c


Study Guide, p. 78

Correcting VisionIn an eye with normal vision, light rays are focused by the

cornea and lens onto the retina. A sharp image is formed on the retina, and the brain interprets the signal as beingclear. However, if the eyeball is too long from front to back,light from distant objects is focused in front of the retina. A blurred image is formed. This condition is callednearsightedness because near objects are seen clearly. To cor-rect nearsightedness, eyeglasses with concave lenses areused. Concave lenses focus these images sharply on theretina. If the eyeball is too short from front to back, light fromnearby objects is focused behind the retina. Again, the imageappears blurred. Convex lenses correct this condition knownas farsightedness. Figure 20-13 shows how lenses are used tocorrect these vision problems. ✔

Convex lensConcave lens

Focal point

Light rays Light rays

Figure 20-12 Light rayspassing through a convex lens arebent toward the center and meetat a focal point. Light rays thatpass through a concave lens arebent outward. They do not meet.

✔Reading Check

What causes

nearsightedness?

Nearsighted Farsighted

Concave lens Convex lens

A A nearsighted person cannot see distant objectsbecause the image is focused in front of the retina.

C A farsighted person cannot see close objectsbecause the image is focused behind the retina.

Figure 20-13 Glasses and contactlenses use concave or convex lenses tosharpen your vision.

B A concave lens corrects nearsightedness. D A convex lens corrects farsightedness.

20-2 THE SENSES 557

20-2 THE SENSES 557

3 AssessCheck for UnderstandingUsing an Analogy

Open up a camera and viewthe internal components tocompare them to the humaneye.

ReteachVisual-Spatial Havestudents make concept

maps of the sensory organs.



L1

Answer to

Reading Check ✔

Nearsightedness is caused by

an eyeball that is too long from

front to back, causing distant

objects to focus in front of

the retina.

Reading Find out how Helen Keller wasable to learn to communicate even thoughshe was deprived of sight and hearing at anearly age. L2


VideodiscGlencoe Science VoyagesInteractive Videodisc—LifeSide 2, Lesson 6 Eyeing Evolution

!7Å/-2^Ö"9312Refer to Videodisc TeacherGuide for additional bar codes.

Page 556: 5a, 5b, 5g, 6c,6d, 6ePage 557: 5a, 5b, 5g, 6c,6d



VisionThink about the different kinds of objects you look at every

day. It’s amazing that, at one glance, you can see the wordson this page, the color illustrations, and your classmate sitting next to you.

Light travels in a straight line unless something bends orrefracts it. Your eyes are equipped with struc-

tures that bend light. As light enters theeye, its waves are first bent by the

cornea and then a lens, as illustratedin Figure 20-11. The lens directs

the rays onto the retina (RETnuh). The retina is a tissue atthe back of the eye that is sen-sitive to light energy. Two typesof cells called rods and conesare found in the retina. Cones

respond to bright light and color.Rods respond to dim light. They

are used to help you detect shapeand movement. Light energy stimu-

lates impulses in these cells. Theimpulses pass to the optic nerve, which car-

ries them to the brain. There, the impulses are inter-preted, and you see what you are looking at.

Lenses—Refraction and FocusLight is refracted, or bent, when it passes through a lens.

Just how it bends depends on the type of lens it passesthrough. A lens that is thicker in the middle and thinner onthe edges is called a convex lens. The lens in your eye is con-vex. If you follow the light rays in Figure 20-12, you’ll see thatthe lens causes parallel light rays to come together at a focuspoint. Convex lenses can be used to magnify objects. Thelight rays enter the eyes in such a way through a convex lensthat the object appears enlarged. Magnifying lenses, handlenses, microscopes, and telescopes all have convex lenses.

A lens that has thicker edges than the middle is called aconcave lens. Follow the light rays in Figure 20-12 as theypass through a concave lens. You’ll see that this kind oflens causes the parallel light to spread out. A concave lens isused along with convex lenses in telescopes to allow distantobjects to be seen clearly.

Optic nerve

Retina

Iris

Lens

Pupil

Cornea

Figure 20-11 Light movesthrough several structures—thecornea and the lens—beforestriking the retina.

PHYSICS INTEGRATION

At four years ofage, a young childcan see clearly at a dis-tance as close as 6.3cm away. As the eye’slens hardens with age,this distance increases.At 30 years old, thedistance is 15 cm. At50 years old, the dis-tance has become40 cm. Estimate howmany times longer thedistance at 30 and 50years old is comparedto the distance clearlyseen at four years old.


Quick DemoObtain a double convex

lens to illustrate the refractionand focusing of light rayssimilar to that which occursin the eye.

EnrichmentHave students research the

phenomenon of afterimage,where an image is still per-ceived after its external causeis gone.

Have students who wear correc-tive eyeglasses examine them todetermine whether the lenses areconcave or convex.

Use the Flex Your Brain activity to have students explore SENSES.

Flex Your BrainFlex Your Brain

at 30 years old, 15 cm �6.3 cm � 2.4 times longer; at 50 years old, 40 cm �6.3 cm � 6.3 times longerthan a four-year-old child

CD-ROMGlencoe Science VoyagesInteractive CD-ROMExplorationsHave students do the interactiveexploration How does humanhearing compare with that ofother animals?

The term fatigue is sometimesused to describe a decreased sensitivity of areceptor, such as the eye, to stimuli. A redsurface seems to become gray when it isstared at for a long period of time, and

the retina is said to be fatigued by long exposure to the color red. The same is trueof hearing. A sustained noise that is heardcontinuously becomes less intense due to fatigue of the processes of the inner ear.

ontent Background

ontentBackground

CC

20-2 THE SENSES 559


1. What is the function ofthe lens in the eye? tofocus light rays onto theretina

2. What are the three smallbones in the middle ear?hammer, anvil, stirrup

3. What are the sensitivenerve cells in your nasalpassages called? olfactorycells

4. Where are the major sen-sory receptors for tastefound? on the tongue

1. sound waves2. eyes: rods and cones;

nose: olfactory cells 3. The body responds to

protect itself or maintainhomeostasis.

4. Think Critically The braincould continue to func-tion when injured, allow-ing you to carry out activ-ities for survival.


AssessmentPerformance Assess students’ abilities tomake and use tables by having them write astatement comparing the different types ofenergy that stimulate the senses. Use Per-formance Assessment in the Science Class-room, p. 87.

Entries should reflectknowledge of the type of skin receptors involved,including touch and tem-perature.

20-2 THE SENSES 559

than another. The four basic taste sensations are sweet, salty,sour, and bitter. Figure 20-14 shows where these tastes arecommonly stimulated on your tongue.

Smell and taste are related. When you have a head coldwith a stuffy nose, food seems tasteless because it is blockedfrom contacting the moist membranes in your nasal passages.

Touch, Pressure, Pain, and TemperatureHow important is it to be able to feel pain inside your

body? Several kinds of sensory receptors in your internalorgans, as well as throughout your skin, respond to touch,pressure, pain, and temperature, as illustrated in Figure 20-15.These receptors pick up changes in touch, pressure, and tem-perature and transmit impulses to the brain or spinal cord.The body responds to protect itself or maintain homeostasis.

Your fingertips have many different types of receptors fortouch. As a result, you can tell whether an object is rough orsmooth, hot or cold, light or heavy. Your lips are sensitive toheat and prevent you from drinking something so hot that itwould burn you. Pressure-sensitive cells in the skin givewarning of danger to a body part and enable you to move toavoid injury.

Your senses are adaptations that help you enjoy or avoidthings around you. You constantly react to your environmentbecause of information received by your senses.

1. What type of stimulus do your ears respond to?2. What are the sensory receptors for the eyes and nose?3. Why is it important to have receptors for pain and pres-

sure in your internal organs?4. Think Critically: The brain is insensitive to pain. What

is the advantage of this?

5. Skill BuilderObserving and Inferring How can you

tell the direction of a sound? Do the Chapter 20 SkillActivity on page 725 to explore how your ears detectsound.

Write a para-graph in your Science

Journal to describe whateach of the followingobjects would feel like.

1. coarse sand from a beach

2. ice cube3. silk blouse4. snake5. smooth rock

Figure 20-15 Many of thesensations picked up by receptorsin the skin are stimulated bymechanical energy. Pressure,motion, and touch are examples.


Assessment

Page 558: 5a, 5b, 7c, 7ePage 559: 5a, 5b



SmellA bloodhound is able to track a par-

ticular scent through fields and forest.Even though your ability to detect odors isnot as sharp, your sense of smell is stillimportant.

You can smell food because it gives offmolecules into the air. Nasal passages contain sensitive nerve cells called olfactorycells that are stimulated by gas molecules.The cells are kept moist by mucous glands.When gas molecules in the air dissolve inthis moisture, the cells become stimulated. Ifenough gas molecules are present, animpulse starts in these cells and travels tothe brain. The brain interprets the stimulus.If it is recognized from previous experience,you can identify the odor. If you can’t recog-nize a particular odor, it is remembered andcan be identified the next time, especially ifit’s a bad one.

TasteHave you ever tasted a new food

with the tip of your tongue and foundthat it tasted sweet? Then when youswallowed it, you were surprised tofind that it tasted bitter. Taste budson your tongue are the major sen-sory receptors for taste. About 10 000

taste buds are found all over yourtongue, enabling you to tell one taste

from another.Taste buds respond to chemical stimuli.

When you think of food, your mouthbegins to water with saliva. This adapta-tion is helpful because in order to tastesomething, it has to be dissolved in water.Saliva begins this process. The solutionwashes over the taste buds, and an impulseis sent to your brain. The brain interpretsthe impulse, and you identify the taste.

Most taste buds respond to several tastesensations. However, certain areas of thetongue seem more receptive to one taste

Comparing Sense of Smell

Procedure

1. Design an experiment to test your classmates’abilities to recognize the odors of differentfoods, colognes, or household products.

2. Record their responses in a data table accord-ing to the gender of the individuals tested.

Analysis

1. Compare the numbers of correctly identifiedodors for both males and females.

2. What can you conclude about the differencesbetween males and females in their ability torecognize odors?

Sweet

Salty

Sour/salty

Bitter

Sour

Figure 20-14 Although yourtaste buds distinguish four sepa-rate taste sensations (A), scientistscannot determine differencesamong individual taste buds (B).

A

B

Purpose

Kinesthetic Studentswill observe the difference

in the sense of smell betweenmales and females.

Materialssmall amounts of various spices,flavor extracts, and other odor-ous substances; cotton balls

Teaching StrategiesSafety Precautions Studentsshould not use any substanceswith strong, noxious odors (e.g.,ammonia). Survey students be-fore class to determine whetherany of them might have allergiesthat might be affected by theodors.Troubleshooting Place asmall amount of the odoroussubstance on a cotton ball foreach sniff test. Do not use thecotton ball for more than oneperson.

Analysis1. Answers may vary, but more

females should correctlyidentify specific odors.

2. Generally, females are moreacutely aware of odors thanare males.

Performance Have studentsconduct a test of identifyingodors while blindfolded. UsePerformance Assessment in the Science Classroom,p. 97.

PCOOP LEARN

ELLL2

Assessment


Senses on the Job Ask students to clipadvertisements in the help wanted sectionof the newspaper about jobs that requirekeenness of certain senses such as hearing,vision, balance and coordination, or smell.

They should put these ads, along withbrief descriptions of how and why specificsenses would be involved, in their ScienceJournals.

Using Scientific MethodsUsing Scientific Methods

Test Your Hypothesis

Analyze Your Data

Draw Conclusions

20-2 THE SENSES 561

Plan1. As a group, agree upon and write

out the hypothesis statement.2. As a group, list the steps you

need to take to test your hypoth-esis. Be specific, describingexactly what you will do at eachstep. Consider the following fac-tors as you list the steps. Howwill you know that sight is not afactor? How will you use the cardshown on the right to deter-mine sensitivity to touch? Howwill you determine and recordthat one or both points of touchare felt? List your materials.

3. Design a data table to use inyour Science Journal.

4. Read over your entire experi-ment to make sure that all stepsare in order.

5. Identify any constants, variables,and controls of the experiment.

Do1. Make sure your teacher

approves your plan and yourdata table before you proceed.

2. Carry out the experiment asplanned.

3. While the experiment is goingon, write down any observa-tions that you make and com-plete the data table in yourScience Journal.

1. Compare your results withthose of other groups.

2. Identify which part of the bodytested can distinguish betweenthe closest stimuli.

3. Identify which part of the bodyis least sensitive.

4. Rank body parts tested frommost to least sensitive. How didyour results compare with yourhypothesis?

1. Based on the results of yourinvestigation, what can you inferabout the distribution of touchreceptors on the skin?

2. What other parts of your bodywould you predict to beless sensitive? Explain yourpredictions.

20-2 THE SENSES 561

have pairs that are 5 mm and 10 mm apart. With a partner’seyes closed, use the part of thecard with toothpicks 1 mm apartand carefully touch the skin sur-face. Caution students not to applyheavy pressure. If the partner feelstwo points, record a plus (�) inthe table. If the partner cannot feelboth points, record a minus (�) inthe table. Repeat using the othersides of the card.

Expected OutcomeThe more sensitive areas of the

skin to touch are the fingertips,palms, and cheeks. Less sensitiveare the back of the hand, forearm,and back of the neck.

Error AnalysisHave students compare their re-

sults and their hypotheses and ex-plain any differences that occurred.

1. Results should be consistent.2. fingertips and usually the

palms3. back of hand, forearm4. Answers will vary.

1. Touch receptors are closer to-gether in the fingertips and fur-ther apart on the back of thehand and forearm. Receptorsin the palm and back of theneck vary.

2. Answers may include theback and the legs becausethey are unlikely to be used togather new information aboutan object.

Analyze Your Data

Draw Conclusions

Performance To further assess students’ understanding of skin sensitivity, repeat this activ-ity on the lower part of the leg and on the foot.Use Performance Assessment in the Science Classroom, p. 17.

Assessment

Have students design an experiment to test thesensitivity of the same body areas to temperatureranges. Caution students not to use extremetemperatures. If they carry out the experiment,be sure their plans are approved first. Page 560: 5a, 5b, 7a, 7c,

7ePage 561: 5a, 5b, 7a, 7c,7e


Activity

20•2Design Your OwnExperiment

Possible Materials• Index card

(3 inches� 5 inches)• Toothpicks• Tape or glue• Metric ruler

Goals• Observe the sensitivity to

touch on specific areas of the body.

• Design an experiment thattests the effects of a variable,such as the closeness of con-tact points, to determine whichbody areas can distinguishbetween the closest stimuli.

Safety PrecautionsDo not apply

heavy pressure when using the toothpicks.

Investigating SkinSensitivity

Your body responds to touch, pressure, and temperature. Not all parts of your body are equally sensitive to stimuli. Some

areas are more sensitive than others. For example, your lips are sen-sitive to heat. This protects you from burning your mouth. Now thinkabout touch. How sensitive is the skin on various parts of your bodyto touch? Which areas can distinguish the smallest amount of dis-tance between stimuli?

What areas of the body are most sensitive to touch?

Based on your experiences, state a hypothesis about which of thefollowing five areas of the body you believe to be most sensitive—fingertip, forearm, back of the neck, palm, and back of the hand.Rank the areas from 5 (the most sensitive) to 1 (the least sensitive).

Activity 20 2Activity 20 2

Recognize the Problem

Form a Hypothesis



Purpose

Interpersonal Studentswill design and carry out an

experiment to determine the sensi-tivity of skin on various parts of thebody by testing for the location ofreceptors in the skin.

Process Skillsobserving and inferring, forming ahypothesis, designing an experi-ment, interpreting data, makingand using tables, comparing andcontrasting

Time2 class periods

MaterialsObtain materials for cooperative

groups. To save time, prepare thetest cards the day before the activ-ity to allow glue to dry.

Safety PrecautionsCaution students not to apply

heavy pressure when using anycontact points device.

Possible HypothesesPossible hypotheses could in-

clude that the whole body isequally sensitive, nerve endingsare various distances apart, andthe most sensitive parts of thebody are the fingertips.

Possible ProceduresPredict which skin areas are the

most sensitive to touch. Rank theareas from most (5) to least (1)sensitive in a data table. Glue thetoothpicks onto the card so thatone side has a pair that are 1 mmapart; another side has a pair 3 mm apart. The other sides

PCOOP LEARN

ELLL2

Recognize the Problem

Form a Hypothesis

Test Your Hypothesis

Sample Data Table

Body part Predictions Felt two points (mm)tested 1 3 5 10

fingertip 5 � � � �

palm 4 � � � �

back of hand 3 � � � �

forearm 1 � � � �

back of neck 2 � � � �

Physically Challenged Any studentwho may not be able to manipulate the test-ing device may be in charge of formulating thehypothesis and the design of the experiment.

Inclusion StrategiesInclusion Strategies

The Pancreas—Playing Two RolesThe pancreas produces a digestive enzyme. This enzyme is

released into the small intestine through tubelike vesselscalled ducts. The pancreas is also part of your endocrine sys-tem because other groups of cells in the pancreas secrete hor-mones. One of these hormones, insulin, enables cells to takein glucose. Recall that glucose is the main source of energy forrespiration in cells. Normally, insulin enables glucose to passfrom the bloodstream through cell membranes. Persons whocan’t make insulin are diabetic because insulin isn’t there toenable glucose to get into cells.

A Negative-Feedback SystemTo control the amount of hormone an endocrine gland

produces, the endocrine system sends chemical informationback and forth to itself. This is a negative-feedback system.It works much the way a thermostat works. When the tem-perature in a room drops below a certain level, a thermostatsignals the furnace to turn on. Once the furnace has raisedthe temperature to the level set on the thermostat, the furnace shuts off. It will stay off until the thermostat signalsagain. In your body, once a target tissue responds to its

Interpreting Blood Sugar Levels

Diabetes results when the pancreas does not produceenough insulin. Insulin is a hormone that enables cellsto take in glucose. Glucose is a sugar needed forenergy. Extra glucose is not stored, so the glucose iscarried in the blood unless insulin enables the cells to take it in. Patients with diabetes have high amountsof sugar in the blood. Normal levels of sugar in themorning are between 60 and 100 milligrams perdeciliter (mg/dL). Eating a meal increases glucose inthe blood.

The graph shows the sugar in the blood from morn-ing to afternoon. Notice the difference in blood sugarsbetween a diabetic and a nondiabetic person.

Think Critically: Approximately how much difference is there in blood sugar levels between thetwo persons first thing in the morning? What might

the diabetic person do to prevent such high readingsone and two hours after breakfast? What mightaccount for the increased level in blood sugar afterthe fourth hour?

1 2 3 4 5 6Hours After Breakfast

Blo

od

Sugar

(mg S

ugar

/d

L B

lood

)

300

250

200

150

100

50

0

diabeticnon-diabetic

Key

20-3 THE ENDOCRINE SYSTEM 563

Visit the GlencoeScience Web Site atwww.glencoe.com/sec/science/ca formore information aboutendocrine diseases.


2 Teach

Diabetes is caused by the lackof insulin or the body’s inabil-ity to use it. The body is un-able to completely metabolizeits sugars, and the kidneyseliminate this unmetabolizedsugar. Blood sugars sometimescan be controlled throughfood choices.

Think Criticallyapproximately 100 mg/dL; eatsmaller amounts of sugar andstarches; a noon meal

3 AssessCheck for UnderstandingActivity

Visual-Spatial On achart or model of the

human body, have studentslocate the endocrine glandsand identify the organs theycontrol.

ReteachVisual-Spatial Using achart of the circulatory

system, have students tracethe pathway of a hormone toits target tissue.



L2

L2

For Internet tips, see Glencoe’s Using the Internet in the Science Classroom.

Internet Addresses

Page 562: 5a, 5bPage 563: 5a, 5b, 7b, 7c



Prepare


1 Motivate

Tying to PreviousKnowledge

Recall from the first sectionin this chapter how the ner-vous system responds tochanges in environment andmakes adjustments in thebody.

SECTION 20•3 The EndocrineSystem

Functions of the Endocrine System“The tallest man in the world!” and “the shortest woman

on Earth!” used to be common attractions in circuses. Thesepeople became attractions because of their extraordinary andunusual height. In most cases, their sizes were the result of amalfunction in their endocrine systems.

The endocrine system is the second control system of yourbody. Whereas impulses are control mechanisms of your ner-vous system, chemicals are the control mechanisms of yourendocrine system. Endocrine chemicals called hormones areproduced in several tissues called glands throughout yourbody. As the hormones are produced, they move directly intoyour bloodstream. Hormones affect specific tissues called target tissues. Target tissues are frequently located in anotherpart of the body at a distance from the gland that affectsthem. Thus, the endocrine system doesn’t react as quickly asthe nervous system. Table 20-1 shows the position of eightendocrine glands and what they regulate.


20 3

How hormones functionThree endocrine glands andthe effects of the hormonesthey produceHow a feedback systemworks

Vocabularyhormonetarget tissue

Endocrine glands control the chemical mechanisms of your body.


It's Important

You'll Learn



It's Important

You'll Learn

It's Important

You'll Learn

Gland Regulates

Pituitary Endocrine glands, which produce hormones;

milk production;growth

Thyroid Carbohydrate use

Parathyroids Calcium

Adrenal Blood sugar;salt and water balance;metabolism

Pancreas Blood sugar

Ovaries Egg production;sex organ development in females

Testes Sperm production; sex organ development in males

Endocrine Glands

Table 20-1Bellringer



Refer to The Pituitary Gland, Distur-bances of Endocrine Function, and Hormone-Producing Bacteria on p. 544F.

ontent Background

ontentBackground

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Reproducible Masters

Critical Thinking/Problem Solving, p. 20

Enrichment, p. 57


Study Guide, pp. 79–80

Transparencies

Teaching Transparency 40 L2

ELLL1

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Resource ManagerCopyright©Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

57

57

LIVING WITH DIABETES

Diabetes is a disease of the endocrine system. It results when the pancreas

does not produce insulin in proper amounts. Insulin is a hormone that

enables the cells of the body to take in sugar in the form of glucose. If not

enough insulin is produced by the pancreas, sugar accumulates in the

bloodstream or is excreted from the body in urine.

1. Why would a person with diabetes need to take insulin in pills or by

injection?

2. Why is maintaining a healthful diet important to a diabetic?

3. Why is it important for a diabetic to get exercise regularly?


Section 20-3


How it WorksA Hearing AidA hearing aid is a small, electronic instrument (left) that makessounds louder and easier to understand. A hearing aid fitsaround the outside of the ear or inside the ear canal. Somehearing aids are so small that they are hardly noticeable.

The tiny microphone built into the hearing aid picks upsounds. It changes sound waves into electrical signals.

The amplifier makes the electrical signals stronger. A hearingaid user can control the degree to which sounds are ampli-fied, or made stronger.

The receiver changes theamplified electrical signalsback into sound signalsand sends them to theeardrum.

The battery is the powersource that makes the hear-ing aid work. Like batteriesin portable tape or CD play-ers, batteries in a hearingaid must be changed whenthey lose power.

Think Critically1. Why must a person be able to hear at some level inorder for a hearing aid to work?2. How might background noise cause problems for peoplewith hearing aids?

An audiologist evaluates and treatspeople with hearing loss. He or sheconducts tests to determine specifichearing problems. Most audiolo-gists have a master’s degree inaudiology (hearing) or speech, lan-guage, and pathology (study ofdiseases). Pretend that you are anaudiologist. Create an advertise-ment about services you canprovide and hearing aids thatyou recommend for peoplewho have trouble hearing.

CareerCONNECTION

How it Works

PARTS OF A HEARING AID

2 3

4

1

1

2

3

4



Thinking Critically1. A hearing aid is an amplification device

only.2. The hearing aids also would amplify

background noise, the person mighthave trouble distinguishing conversa-tion or sounds from the radio or TV ifbackground noise also is loud.

PurposeStudents are introduced to ahearing aid and the differentparts that make it work.

Sailors invented hearing aidslong ago. They used ear trum-pets to communicate overlong distances. By 1900, hear-ing aids were available. Ahearing aid usually helpshearing when the outer ear ormiddle ear is damaged.

ontent Background

ontentBackground

CC

Have students cup theirhands behind their earsand have another studentmake a sound. Comparethe sound with normalhearing. Cupping yourhand behind your ear am-plifies the sound like ahearing aid.

LearningVISUAL

Teaching StrategiesHave students design theirown speaking tubes that willamplify their voices. Com-pare the different voiceswhen the tube is coiled andwhen it is straightened. Stu-dents can make the speakingtube by using a cardboardpaper-towel holder, tape, anda funnel. Tape the funnel toone end of the tube. Discusshow the amplification of thetube is like the amplificationof a hearing aid.

CareerCONNECTION

Audiologists need to complete a two-yearpostgraduate training course before theycan work. They need to have an undergrad-uate degree such as a Bachelor of Arts or Sci-ence before they can apply for the course.

Page 564: 5a, 5bPage 565: 5a, 5b




1. What type of glands donot have ducts? endocrine

2. What is one of the hor-mones produced by thepancreas? insulin

3. What signals a gland tostart secreting its hor-mone again? when thelevel of hormone in thebloodstream drops

1. They are endocrine secre-tions that control activi-ties in parts of the bodynot near the gland.

2. a system that uses thelevel of hormone in theblood to signal when agland should secrete thehormone again

3. Refer to Table 20-1 forpossible answers.

4. Think Critically Insulinenables glucose to passfrom the bloodstreaminto cells. Cells need glu-cose for respiration. With-out insulin, cells can’trespire.


AssessmentPerformance Write a paper explaining thesimilarities and differences of the nervousand endocrine systems. Use the Perfor-mance Assessment in the Science Class-room, p. 87.

5. Skill BuilderBoth systems send and receivemessages. They also help

maintain homeostasis.Entries may include thatdiabetics are people whocan’t make insulin. Thisprevents glucose from en-tering cells. Diabetes canbe controlled, however.


hormone, the tissue sends a chemical signal back tothe gland. This signal causes the gland to stop or slowdown production of the hormone. When the level ofthe hormone in the bloodstream drops below a certainlevel, the endocrine gland is signaled to begin secret-

ing the hormone again. In this way, the concentra-tion of the hormone in the bloodstream is

kept at the needed level. Figure 20-16illustrates how a negative-feedback sys-

tem works.Hormones produced by endocrine

glands go directly into the blood-stream and affect target tissues. Thelevel of the hormone is controlledby a negative-feedback system. In this way, many chemicals inthe blood and body functions arecontrolled.

1. What is the function of hormones?2. What is a negative-feedback system?3. Choose one hormone and explain how it works.4. Think Critically: Glucose passes from the blood-

stream through cell membranes and into the cells.Glucose is required for respiration within cells. How would lack of insulin affect this process?

5. Skill BuilderComparing and Contrasting In what ways

are the nervous system and endocrine system alike? Ifyou need help, refer to Comparing and Contrasting in theSkill Handbook on page 684.


Pretend youare a doctor and

have to explain to ayoung patient aboutdiabetes. What wouldyou say to him?

Hormone productionslows down

Hormone productionincreases

Hormonelevellow

Hormonelevelhigh

ON

OFF

ON

OFF

Figure 20-16 Many internalbody conditions, such as hormonelevel and body temperature, are con-trolled by negative-feedback systems.

A Feedback System

ISUALIZINGV

ISUALIZING

G

V ISUALIZINGV

Figure 20-16 Have stu-dents describe what ishappening at each point ofthe cycle. Have them tellhow this system is like thethermostat in a home.

LearningVISUAL

CHAPTER 20 REVIEWING MAIN IDEAS 567

Answers to QuestionsSection 20-1Body Regulation Some ofthe body functions that areconstantly being checked areheartbeat, breathing, and hor-mone levels in the blood-stream.

Nervous System The twomajor divisions of the ner-vous system are the centralnervous system (CNS) andthe peripheral nervous sys-tem (PNS).

Section 20-2Senses The senses involvedare sight, smell, touch, andtaste.

Section 20-3Endocrine System The glandreleases its secretion into thebloodstream, which carries itto a specific site anywhere inthe body.

Portfolio Encourage students to place intheir portfolios one or two items of whatthey consider to be their best work. Exam-ples include: • Science Journal, p. 547• MiniLab, p. 558• Activity 20-2, pp. 560–561

Performance Additional performance as-sessments may be found in PerformanceAssessment and Science Integration Ac-tivities. Performance Task Assessment Listsand rubrics for evaluating these activitiescan be found in Glencoe’s Performance As-sessment in the Science Classroom.

P

Assessment

CD-ROMGlencoe Science VoyagesInteractive CD-ROMChapter Summaries and QuizzesHave students read theChapter Summary then take theChapter Quiz to determinewhether they have masteredchapter content.

CHAPTER 20 REVIEWING MAIN IDEAS 567

✔Reading Check

List two or three gen-

eralizations about the

nervous and endocrine

systems. Exchange lists

and determine if they

are accurate.

Section

20-3 THE ENDOCRINE SYSTEM

Endocrine glands secretehormones directly into your bloodstream.Hormones affect specific tissues through-out the body and regulate their activities.A feedback system regulates the hormonelevels in your blood. How can a glandthat is near your head control therate of chemical activities throughoutyour entire body?

Section

20-2 THE SENSES

Your senses respond to energy. The eyes respond to light, and the ears respond to sound waves. Theolfactory cells of the nose and the taste budsof the tongue are stimulated by chemicals.What senses are involved as youpick up and eat a freshly bakedchocolate chip cookie?

Chapter

20ReviewingMain Ideas


Reviewing Main Ideas canbe used to preview, review,reteach, and condense chap-ter content.

Preview

Linguistic Have stu-dents try to answer the

questions in their ScienceJournals. Use student an-swers as a source for discus-sion throughout the chapter.

Review

Interpersonal Havestudents answer the

questions on separate piecesof paper and compare theiranswers with those of otherstudents in the class.

Reteach

Visual-Spatial Havestudents look at the il-

lustrations on these pages.Ask them to describe detailsthat support the main ideas ofthe chapter found in the state-ment for each illustration.

Auditory-Musical If

time does not permit

teaching the entire chap-

ter, use the information on

these pages along with the

chapter Audiocassettes to

present the material in a

condensed format.

OUT OF

TIME?

Arrow-Poison Frogs Skin glands ofarrow-poison frogs secrete a powerfulvenom that results in muscular paralysis. Anamount as small as 0.000 01 g can kill ahuman. Have students find out how the na-tive peoples of Central and South Americaextract the venom and how they use it tohunt. L2

Cultural DiversityCultural Diversity

For a preview of thischapter, study this

Reviewing Main Ideasbefore you read the chapter.After you have studied thischapter, you can use theReviewing Main Ideas toreview the chapter.

The GlencoeMindJogger,Audiocassettes,and CD-ROM

provide additionalopportunities for review.

Chapter Reviewing Main IdeasChapter Reviewing Main Ideas20

Section

20-1 BODY REGULATION

Your body is constantlyreceiving a variety of stimuli frominside and outside the body. Thenervous and endocrine systemsrespond to these stimuli to main-tain homeostasis. What are somebody functions that are con-stantly being checked and regulated?


NERVOUS SYSTEM

The basic unit of the nervous system is the neuron. Stimuli aredetected by sensory neurons, and theimpulse is carried to an interneuronand then transmitted to a motor neu-ron. The result is the movement of abody part. Some responses are auto-matic and are called reflexes. Whatare the two major divisions of thenervous system?

CHAPTER 20 ASSESSMENT 569

The Test-Taking Tip waswritten by The Princeton Re-view, the nation’s leader intest preparation.

1. A2. D

22. cerebrum—memory,senses, thinking; cerebel-lum—voluntary muscles,balance, muscle tone;brain stem—coordinatinginvoluntary muscle move-ments, controlling heart-beat, breathing, and bloodpressure

23. Concept map should in-clude the following steps:cornea—lens—retina—optic nerve—brain.

24. A nerve-transmitt ingchemical is released fromthe axon of one neuron,d i f f u s e s a c ro s s t h esynapse, and starts an im-pulse in the next neuron.

25. It may be lacking thenerve-transmitting chem-ical released by the axon.

26. Ways to improve balancecould include practicing,exercising, and takingdance lessons.

Bonus Question

How is your endocrinesystem like the thermostat ina house? According to the levelof hormone in the blood, targettissue sends a chemical messageback to the gland to stop or starthormone secretion. Likewise, thethermostat in a house signals theheating or air conditioning unitto start or stop according to thetemperature in the house.

Test Practice

The Test Practice Workbook provides studentswith practice in the format, concepts, and criti-cal-thinking skills tested in standardized exams.

Reproducible MastersChapter Review, pp. 39–40 Performance Assessment, p. 20 Assessment, pp. 77–80

Glencoe Technology

Chapter Review Software

Computer Test Bank

MindJogger Videoquiz

L2

L2

L2

Assessment Resources

TEST-TAKING

CHAPTER 20 ASSESSMENT 569

Test-Taking Tip

What does the test expect of me?Find out what concepts, objectives, orstandards are being tested before thetest. Keep those concepts in mind as youanswer the questions.

Test Practice

Use these questions to test your ScienceProficiency.

1. What happens to an endocrine glandwhen the blood level of its hormone isincreased?A) The gland stops producing hormones

until the hormone level in the bloodfalls below a certain point.

B) The gland continues producing hor-mones until the blood can’t hold anymore hormones.

C) All endocrine glands keep producingtheir hormones until all hormone lev-els in the blood are equal.

D) All endocrine glands stop producinghormones until all hormone levels inthe blood are balanced.

2. Which statement below is the correctpathway from the stimulus to theresponse in a reflex response?A) receptor—interneuron—brain—motor

neuron—muscleB) sensory neuron—brain—spinal

cord—motor neuronC) muscle—receptor—sensory neuron—

interneuron—motor neuronD) receptor—sensory neuron—inter-

neuron—motor neuron—muscle

Developing Skills

If you need help, refer to the Skill Handbook.

21. Classifying: Classify the types of neurons as to their location and direction of impulse.

22. Comparing and Contrasting: Compareand contrast the structures and functionsof the cerebrum, cerebellum, and brainstem. Include in your discussionthe following functions: balance, in-voluntary muscle movements, muscle tone, memory, voluntary muscles, thinking, and senses.

23. Concept Mapping: Prepare a conceptmap showing the correct sequence of thestructures through which light passes inthe eye.

24. Interpreting Scientific Illustrations:Using the following diagram of thesynapse, explain how an impulse movesfrom one neuron to another.

25. Observing and Inferring: If an impulsetraveled down one neuron, but failed tomove on to the next neuron, what mightyou infer about the first neuron?

26. Predicting: Refer to the Try at HomeMiniLab in Section 20-2 and predictways to improve your balance. Test yourprediction.

AssessmentAssessment


Using Vocabulary

1. n2. i3. c4. l5. d

To reinforcechapter vo-

cabulary, use the Study Guidefor Content Mastery booklet.Also available are activities forGlencoe Science Voyages onthe Glencoe Science Web Site.www.glencoe.com/sec/science/ca

Checking Concepts

6. D 11. C7. B 12. A8. C 13. C9. C 14. C

10. A 15. D

Thinking Critically

16. Accept all reasonable responses; so messagesdo not get mixed; so thatresponses can be coordi-nated.

17. Reflexes are automaticacts that occur withoutour thinking about them.Therefore, they happenquickly and can shield ourbodies from danger suchas sharp or hot objects.

18. The doctor might check tosee if the pancreas wasproducing enough insulin.

19. Examples include giant-ism, dwarfism, or diabetes.

20. The skin on your face has more neuronsor more closely arranged neurons thanthe skin on your back. The sense oftouch is more pronounced on the face.You could check this out with a series oftests using something lightweight, suchas a feather or paintbrush hair to testsensitivity of the face and neck.

Developing Skills

21. Sensory neurons are located in the senseorgans and spinal cord and carry im-pulses to the brain. Interneurons are lo-cated in the central nervous system andcarry impulses from the central nervoussystem to motor neurons. Motor neu-rons are in muscles and glands andcarry impulses from brain to musclesand glands.

Chapter AssessmentChapter Assessment20


10. What part of the brain controls voluntarymuscle?A) cerebellum C) cerebrumB) brain stem D) pons

11. What is the part of the brain that isdivided into two hemispheres?A) pons C) cerebrumB) brain stem D) spinal cord

12. What is controlled by the somatic divi-sion of the PNS?A) skeletal musclesB) heartC) glandsD) salivary glands

13. Which of the following are endocrinechemicals produced in glands?A) enzymes C) hormonesB) target tissues D) saliva

14. Which gland controls many otherendocrine glands throughout the body?A) adrenal C) pituitaryB) thyroid D) pancreas

15. Which of the following does the innerear contain?A) anvil C) eardrumB) hammer D) cochlea

Thinking Critically

16. Why is it helpful to have impulses movein only one direction in a neuron?

17. How are reflexes protective?

18. You have had your blood tested forsugar, and the doctor says you have aproblem. How might your doctor deter-mine which gland is responsible for thisregulation problem?

19. Describe an example of a problem thatresults from improper gland functioning.

20. If a fly were to land on your face andanother one on your back, which mightyou feel first? Explain how you wouldtest your choice.

a. axonb. brain stemc. central nervous

systemd. cerebellume. cerebrumf. cochleag. dendriteh. hormone

i. neuronj. olfactory cellk. peripheral

nervous systeml. reflex

m. retinan. synapseo. target tissuep. taste bud

Match each phrase with the correct term fromthe list of Vocabulary words.

1. a small space between neurons2. basic unit of nervous system3. division containing brain and spinal cord4. an automatic response to stimuli5. center for coordination of voluntary

muscle action

Checking Concepts

Choose the word or phrase that best answersthe question.

6. How do impulses cross synapses?A) by osmosisB) through interneuronsC) through a cell bodyD) by a chemical

7. What are the neuron structures thatcarry impulses to the cell body?A) axons C) synapsesB) dendrites D) nuclei

8. What are neurons detecting stimuli inthe skin and eyes called?A) interneurons C) sensory neuronsB) motor neurons D) synapses

9. What is the largest part of the brain?A) cerebellum C) cerebrumB) brain stem D) pons

Using Vocabulary

Chapter

20Assessment


Chapter 20: The Nervous and Endocrine Systems · 2019-11-07 · Nervous and Endocrine Systems...

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