chapter 36: the nervous system · 2018-10-05 · 36.1 the nervous system 975 na + na+ na gated k+...

Chapter 36 OrganizerChapter 36 Organizer

Activities/FeaturesObjectivesSection

MATERIALS LIST

BioLabp. 996 microscope, microscope slides,dropper, aged tap water, Daphnia cul-ture, dilute solutions of coffee, tea,cola, ethyl alcohol, tobacco, and coughmedicine

MiniLabsp. 980 meterstick, paper, pencilp. 991 paper, pencil

Alternative Labp. 980 paper clips, metric ruler, paper,pencil

Quick Demosp. 975 telephone cablep. 981 rubber hammerp. 984 tape recording of commonsoundsp. 990 samples of non prescriptiondrugs

Need Materials? Contact Carolina Biological Supply Company at 1-800-334-5551or at http://www.carolina.com

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Teacher Classroom Resources

Assessment Resources Additional Resources

Products Available FromGlencoeTo order the following products,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 FromNational Geographic SocietyTo order the following products,call National Geographic Societyat 1-800-368-2728:VideosIncredible Human MachineNervous System (Human BodySeries)

Teacher’s Corner

972B

The Nervous SystemThe Nervous System

TransparenciesReproducible MastersSection

The NervousSystem

The Senses

The Effects ofDrugs

Section 36.1

Section 36.2

Section 36.3

Teacher Classroom Resources

Reinforcement and Study Guide, pp. 159-160Critical Thinking/Problem Solving, p. 36BioLab and MiniLab Worksheets, p. 159Laboratory Manual, pp. 261-264Content Mastery, pp. 177-178, 180

Reinforcement and Study Guide, p. 161Concept Mapping, p. 36Laboratory Manual, pp. 265-268Content Mastery, pp. 177, 179-180Tech Prep Applications, pp. 47-48

Reinforcement and Study Guide, p. 162BioLab and MiniLab Worksheets, pp. 160-162Content Mastery, pp. 177, 180Tech Prep Applications, pp. 49-50 L2

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Section Focus Transparency 87Basic Concepts Transparency 67

Section Focus Transparency 88Basic Concepts Transparency 68Basic Concepts Transparency 69Reteaching Skills Transparency 52Reteaching Skills Transparency 53

Section Focus Transparency 89

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Assessment Resources Additional ResourcesSpanish ResourcesEnglish/Spanish AudiocassettesCooperative Learning in the Science ClassroomLesson Plans/Block Scheduling

COOP LEARN

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Chapter Assessment, pp. 211-216MindJogger VideoquizzesPerformance Assessment in the Biology ClassroomAlternate Assessment in the Science ClassroomComputer Test BankBDOL Interactive CD-ROM, Chapter 36 quiz

Refer to pages 4T-5T of the Teacher Guide for an explanation of the National Science Education Standards correlations.

The Nervous SystemNational Science EducationStandards UCP.1-3, UCP.5;A.1; B.1, B.3; C.1, C.5, C.6 (2 sessions, 1 block)

The SensesNational Science EducationStandards UCP.1-3, UCP.5;C.1, C.5, C.6 (1 session)

The Effects of DrugsNational Science EducationStandards UCP.1, UCP.2;A.1, A.2; C.6; E.1, E.2; F.1,F.5, F.6; G.1, G.2 (2 sessions,1/2 block)

1. Analyze how nerve impulses travelwithin the nervous system.

2. Recognize the functions of the majorparts of the nervous system.

3. Compare voluntary responses and involuntary responses.

4. Define the role of the senses in thehuman nervous system.

5. Recognize how senses detect chemical,light, and mechanical stimulation.

6. Identify ways in which the senses worktogether to gather information.

7. Recognize the medicinal uses of drugs.8. Identify the different classes of drugs.9. Interpret the effect of drug misuse and

abuse on the body.

Focus On Evolution of the Brain, p. 978MiniLab 36-1: Distractions and ReactionTime, p. 980BioTechnology: Scanning the Mind, p. 998

Inside Story: The Eye, p. 985Problem-Solving Lab 36-1, p. 986

Problem-Solving Lab 36-2, p. 989Careers in Biology: Pharmacist, p. 990MiniLab 36-2: Interpret a Drug Label, p. 991Design Your Own BioLab: What drugsaffect the heart rate of Daphnia? p. 996

Section 36.2

Section 36.1

Section 36.3

Key to Teaching StrategiesKey to Teaching Strategies

Level 1 activities should be appropriatefor students with learning difficulties.Level 2 activities should be within theability range of all students.Level 3 activities are designed for above-average students.ELL activities should be within the abilityrange of English Language Learners.

Cooperative Learning activitiesare designed for small group work.These strategies represent student prod-ucts that can be placed into a best-workportfolio.These strategies are useful in a blockscheduling format.

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The following multimedia resources are available from Glencoe.

Biology: The Dynamics of LifeCD-ROM

BioQuest: Body SystemsAnimation: Impulse Transmission in a Motor NeuronAnimation: Impulse Transmission Across a SynapseAnimation: The Sense of SightAnimation: The Sense of Hearing

Videodisc ProgramImpulse TransmissionImpulse Transmission: SynapseSense of Sight

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http://www.carolina.com

Section

Neurons: Basic Units ofthe Nervous System

The basic unit of structure andfunction in the nervous system is theneuron, or nerve cell. Neurons (NYU ronz) conduct impulses through-out the nervous system. As shown inFigure 36.1, a neuron is a long cellthat consists of three regions: a cellbody, dendrites, and an axon.

Dendrites (DEN drites) arebranchlike extensions of the neuronthat receive impulses and carry themtoward the cell body. The axon is asingle extension of the neuron thatcarries impulses away from the cellbody and toward other neurons, mus-cles, or glands.

Neurons fall into three categories:sensory neurons, motor neurons, andinterneurons. Sensory neurons carryimpulses from the body to the spinal

cord and brain. Interneurons arefound within the brain and spinalcord. They process incoming impulsesand pass response impulses on tomotor neurons. Motor neurons carrythe response impulses away from the brain and spinal cord to a muscleor gland.

36.1 THE NERVOUS SYSTEM 973

What do you use the telephonefor? To communicate with afriend in another location.

You may know that your message istransmitted as an electrical impulseacross the telephone wires. Would itsurprise you to know that a similarelectrical impulse travels throughyour body, helping some parts to communicate with others?

SECTION PREVIEW

ObjectivesAnalyze how nerveimpulses travel withinthe nervous system.Recognize the func-tions of the major partsof the nervous system.Compare voluntaryresponses and involun-tary responses.

Vocabularyneurondendriteaxonsynapseneurotransmittercentral nervous systemperipheral nervous

systemcerebrumcerebellummedulla oblongatasomatic nervous systemreflexautonomic nervous

systemsympathetic nervous

systemparasympathetic

nervous system

36.1 The Nervous System

Dendrites

Nucleus

Cell body

Axon

Axonendings

Myelin sheath

Figure 36.1Dendrites and axonsare extensions thatbranch out from thecell body of a neuron.

Like telephone wires betweenhomes, nerve cells relay mes-

sages within the human body.

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Section 36.1

BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES

Use with Chapter 36,Section 36.1

What action causes the boy’s response?

Give an example of a similar stimulus-response combination in the human body.

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PrepareKey ConceptsThe method by which impulsestravel in the nervous system—including electrical transmissionalong the neuron and chemicaltransmission at the synapse—arecovered in this section. The orga-nization and function of themajor parts of the nervous systemare discussed.

Planning■ Obtain a piece of cable for the

first Quick Demo.■ Collect enough metersticks for

student use in MiniLab 36-1.■ Acquire a rubber hammer for

the second Quick Demo.

1 FocusBellringer Before presenting the lesson, display Section Focus Trans-parency 87 on the overhead pro-jector and have students answerthe accompanying questions.

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LS972 THE NERVOUS SYSTEM

The Nervous System

What You’ll Learn■ You will relate the structure

of a nerve cell to the trans-mission of a nerve signal.

■ You will identify the sensesand their signal pathways.

■ You will compare and contrast various types ofdrugs and their effects on the nervous system.

Why It’s ImportantThe nervous system helps youperceive and react to the worldaround you. By understandinghow drugs—both legal and illegal—affect the function ofthe nervous system, you willdiscover their role in treatingmedical disorders, and the danger they pose if misused.

Swapping ColorsDraw a picture of a green treewith red dots all over it. Stareat the drawing for one fullminute. Then look at a sheet ofwhite paper. What do you see?

To find outmore about

the nervous system, visit theGlencoe Science Web Site.www.glencoe.com/sec/science

36

When nerve cells (inset) in youreyes detect something scary,they relay a message to yourbrain, which, in turn, tells yourmuscles to tense up and yourheart to beat faster.

GETTING STARTEDGETTING STARTED

ChapterChapter

Magnification:5550�

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Theme DevelopmentThe major theme in this chapteris systems and interactions.Stress that the nervous systemreceives information from allbody systems and responds inorder to maintain homeostasis inthe body.

Chapter 36Chapter 36

MultipleLearningStyles

Look for the following logos for strategies that emphasize different learning modalities.Kinesthetic Portfolio, p. 975;Quick Demo, p. 981; Project,

p. 983Visual-Spatial Meeting Individual Needs, pp. 974, 988;

Reinforcement, p. 975; Display, p. 984; Portfolio, p. 985; Check for Understandning, p. 987

Interpersonal Biology Journal,p. 994

Intrapersonal Enrichment, p. 994;Concept Development, p. 994Linguistic Biology Journal, pp. 974, 976, 977, 984, 990, 992;

Enrichment, pp. 976, 977; Tech Prep, p. 976; Project, p. 977; Portfolio, p. 993;Check for Understanding, p. 994;Reteach, p. 994

Auditory-Musical Quick Demo, p. 984

GETTING STARTED DEMOGETTING STARTED DEMO

Create a loud noise by slam-ming a book on your desk.Use student reaction to begina discussion of how the ner-vous system reacts to environ-mental stimuli, including loudnoises.

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If time does not permit teach-ing the entire chapter, use theBioDigest at the end of theunit as an overview.

Assessment PlannerAssessment PlannerPortfolio Assessment

Portfolio, TWE, pp. 975, 985, 993Alternative Lab, TWE, pp. 980-981Problem-Solving Lab, TWE, p. 986

Performance AssessmentMiniLab, SE, pp. 980, 991BioLab, SE, pp. 996-997Alternative Lab, TWE, pp. 980-981 Assessment, TWE, p. 977MiniLab, TWE, p. 991

BioLab, TWE, pp. 996-997Knowledge Assessment

Section Assessment, SE, pp. 982, 987, 995Chapter Assessment, SE, pp. 999-1001Assessment, TWE, pp. 984, 987, 995Problem-Solving Lab, TWE, p. 989

Skill AssessmentAssessment, TWE, pp. 982, 992MiniLab, TWE, p. 980

Internet Address Book

NoteInternet

addresses that you find usefulin the space below for quickreference.

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


Na+

Na+

Na+

Gated K+ channel

Impulse

Outside cell

Gated Na+

channel Inside cell

K+

Figure 36.4A wave of depolarization moves down the axon of a neuron.

View an animation of nerve depo-larization in the Presentation Builder ofthe Interactive CD-ROM.

CD-ROM

the plasma membrane is said to bepolarized. A polarized membrane hasthe potential to transmit an impulse.

How an impulse is transmittedWhen a stimulus excites a neuron,

gated sodium channels in the mem-brane open up and sodium ions rushinto the cell. As the positive sodiumions build up inside the membrane, theinside of the cell becomes more posi-tively charged than the outside. Thischange in charge, called depolarization,moves like a wave down the length ofthe axon, as seen in Figure 36.4. Asthe wave passes, gated channels andthe Na+/K+ pump act to return theneuron to its resting state, with theinside of the cell negatively chargedand the outside positively charged.

An impulse can move down thecomplete length of an axon onlywhen stimulation of the neuron isstrong enough. If the thresholdlevel—the level at which depolariza-tion occurs—is not reached, theimpulse quickly dies out.

White matter and gray matterMost axons are surrounded by a

white covering of cells called themyelin sheath. Like the plastic coatingon an electric wire, the myelin sheathtightly insulates the axon, hinderingthe movement of ions across its plasmamembrane. The ions move quicklydown the axon until they reach a gapin the sheath. At this point, the ionspass through the plasma membraneof the nerve cell and depolarizationoccurs. As a result, the impulse jumpsfrom gap to gap, greatly increasingthe speed at which it travels.

Gated sodium channels open, allowing sodium ions to enterand make the inside of the cell positively charged and the outside negatively charged.

AA

Gated K+ channel Gated K+ channel

Na+

Na+/K+

pumpNa+

K+

K+

Gated Na+

channelGated Na+

channel

Impulse

As the impulse passes, gated sodium channels close, stop-ping the influx of sodium ions. Gated potassium channelsopen, letting potassium ions out of the cell. This actionrepolarizes the cell.

BB

Gated K+ channel

Na+/K+

pump 2K+

3Na+

Gated Na+

channel

Impulse

CC As gated potassium channels close, the Na+/K+ pump restoresthe ion distribution.

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ReinforcementVisual-Spatial Have studentsdraw neurons similar to

Figures 36.3 and 36.4, label theparts, and use arrows to show thepathway of the nerve impulse.

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Relaying an impulseSuppose you’re in a crowded, noisy

store and you feel a tap on yourshoulder. Turning your head, you seethe smiling face of a good friend.How did the shoulder tap get yourattention? The touch stimulated sen-sory receptors located in the skin ofyour shoulder to produce an impulse.The sensory impulse was carried tothe spinal cord and then up to yourbrain. From your brain, an impulsewas sent out to your motor neurons,which then transmitted the impulseto muscles in your neck. Your neckmuscles then turned your head.Figure 36.2 shows how a stimulus,such as a tap on the shoulder, is trans-mitted through your nervous system.

A neuron at restFirst, let’s look at a resting neu-

ron—one that is not transmitting animpulse. You have learned that theplasma membrane controls the con-centration of ions inside a cell. Becausethe plasma membrane of a neuron ismore permeable to potassium ions(K+) than it is to sodium ions (Na+),more potassium ions exist within thecell membrane than outside it.Similarly, more sodium ions exist out-side the cell membrane than within it.

The neuron membrane also con-tains an active transport system, calledthe sodium/potassium (Na+/K+)pump, which uses ATP to pump threesodium ions out of the cell for everytwo potassium ions it pumps in. Asyou can see in Figure 36.3, the actionof the pump increases the concentra-tion of positive charges on the outsideof the membrane. In addition, thepresence of many negatively chargedproteins and organic phosphatesmeans that the inside of the mem-brane is more negatively charged thanthe outside. Under these conditions,which exist when the cell is at rest,

974 THE NERVOUS SYSTEM

Openion channel

Plasma membrane Outside cell

GatedNa+ channel

Openion channel

GatedNa+ channel

Na+/K+

pump

Inside cell

Figure 36.2The nervous system sorts and interprets incoming information before directing a response.

Figure 36.3The membrane of a neuron contains open as well asgated channels that allow movement of sodium (Na+)and potassium (K+) ions into and out of the cell.

Receptors in the skin sensea tap or other stimulus.

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Sensory neurons trans-mit the touch message.

BB

The message is inter-preted. A response is sent to the motorneurons.

CC

Motor neurons trans-mit a response mes-sage to the shouldermuscles.

DD

The neck muscles areactivated, causing thehead to turn.

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2 TeachVisual LearningFigure 36.2 Spend a few minutesreviewing the sequence of eventsinvolved in the nervous system’sresponse to a stimulus. Ask stu-dents what path the nervous sys-tem would take to turn the headin response to a sound such as ahonking car horn. The path wouldbe the same except for the initialreceptors, which would be located inthe ear rather than in the skin.

Visual LearningFigure 36.3 Ask: What effectdoes the Na+/K+ pump have onthe charge of the normal restingneuron? It maintains a positivecharge on the outside of the mem-brane and a negative charge withinthe membrane of a resting neuron.

MEETING INDIVIDUAL NEEDS MEETING INDIVIDUAL NEEDS

GiftedVisual-Spatial Have gifted studentsprepare a labeled dissection of a

sheep brain. They should prepare wholebrains and half brains, labeling areas dis-cussed in Chapter 36. Brains for this activ-ity can be ordered from biological supplyhouses.

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BIOLOGY JOURNAL BIOLOGY JOURNAL

Nerve AnalogyLinguistic Have students write aparagraph that explains how a

nerve is similar to a wire going from acontrolling switch (stimulus) to a lightbulb (effector).

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Quick DemoQuick Demo

To demonstrate what a nerve islike, show students the end ofa cable, such as a telephonecable. Compare each wire to anaxon and the individual wirewrappings to myelin sheaths.Explain that the whole cablerepresents a nerve.

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CD-ROMBiology: The Dynamicsof Life

BioQuest: Body SystemsDiscs 1-5

VIDEODISCBiology: The Dynamicsof Life

Impulse Transmission: Neuron(Ch. 37)Disc 2, Side 1, 1 min. 24 sec.

!:r}"

Resource ManagerResource Manager

Section Focus Transparency 87and Master

Critical Thinking/ProblemSolving, p. 36 L3

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Using a ModelKinesthetic Ask students to obtain asmall cable of wires, such as that used

in the Quick Demo above. Have them mountthe cable on a sheet of paper and draw anerve beside it. Ask the students to write aparagraph that compares and contrasts the

nerve and the cable. Similarities include thefollowing: Both carry messages, connect twothings, contain a bundle of “wires,” and havea covering. Differences include the following:The nerve is alive, made of cells, and canrepair itself to a degree.

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PortfolioPortfolio

Exploring NursingHave students interested innursing contact a local hospi-tal and arrange to shadow anurse for an afternoon to findout more about what theseprofessionals do. L2

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Animation: Impulse Transmis-sion in a Motor Neuron, Disc 5

Two systems work togetherAnother division of your nervous

system, called the peripheral nervoussystem (puh RIHF rul), is made up ofall the nerves that carry messages toand from the central nervous system.It is similar to the telephone wires thatrun between a phone system’s controlcenter and the phones in individualhomes. Together, the central nervoussystem (CNS) and the peripheralnervous system (PNS), shown inFigure 36.6, respond to stimuli fromthe external environment.

Anatomy of the brainThe brain is the control center of

the entire nervous system. Fordescriptive purposes, it is useful todivide the brain into three main sec-tions: the cerebrum, the cerebellum,and the brain stem.

The cerebrum (suh REE brum) isdivided into two halves, called hemi-spheres, that are connected by bun-dles of nerves. Your conscious activi-ties, intelligence, memory, language,skeletal muscle movements, andsenses are all controlled by the cere-brum. The outer surface of the cere-brum, called the cerebral cortex, ismade up of gray matter. The cerebralcortex contains countless folds andgrooves that increase its total surfacearea. This increase in surface areaplayed an important role in the evo-lution of human intelligence asgreater surface area allowed moreand more complex thought processes.

The cerebellum (ser uh BEL um),located at the back of your brain, con-trols your balance, posture, and coor-dination. If the cerebellum is injured,your movements become jerky.

The brain stem is made up of themedulla oblongata, the pons, and themidbrain. The medulla oblongata(muh DUL uh • ahb long GAHT uh) isthe part of the brain that controls


Brain

Spinalcord

Figure 36.6The human nervous system is madeup of the CNS, in pink, and the PNS,in yellow. The brain and spinal cordare protected by the skull and thevertebrae, respectively.

involuntary activities such as breath-ing and heart rate. The pons andmidbrain act as pathways connectingvarious parts of the brain with eachother. Find out more about how thebrain evolved by reading Focus OnEvolution of the Brain. For the lateston technological advances in brainimaging, check out the BioTechnologysection at the end of the chapter.

Brain Skull

Vertebra

Spinal cord

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EnrichmentLinguistic The Chinese haveused acupuncture as a com-

plete system of medicine forthousands of years. The proce-dure involves inserting long, thinneedles into specific areas of thepatient’s body. Electrical impulsesare then sent down the length ofthe needles. Acupuncture is usedto relieve pain, cure cancer, andeverything in between. It is alsocurrently being used in China asa form of anesthesia for patientsundergoing surgery.

Have students research andreport on ancient methods ofacupuncture. How did the meth-ods used then differ from thoseused today? The needles used to beturned to achieve the desired effect.Now electrical impulses are usedinstead.

Performance Assessmentin the Biology Classroom, p. 49,Preparing and Teaching a LessonAbout the Nervous System. Havestudents carry out this activity todemonstrate their knowledge ofthe structure and function of thenervous system. L2

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AssessmentAssessment

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LSAxon

Calciumchannel

Synapse

Synapticspace

Vesicle withneurotransmittersinside

Neurotransmitterdiffuses acrosssynapse and bindswith receptor ondendrite

Vesicle fuseswithmembrane(exocytosis)

Neurotrans-mittersreleased intosynapse

Dendrite

Dendrite

DendriteAxon

Ion channel

Ca++ Ca++

Ca++Axon

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synaptic space by exocytosis. Thesechemicals, called neurotransmitters,diffuse across the space to the den-drites of the next neuron. As the neu-rotransmitters reach the dendrites,they signal receptor sites to open theion channels. These open channelschange the polarity in the neuron,initiating a new impulse. Enzymes inthe synapse typically break down theneurotransmitters shortly after trans-mission, preventing the continual fir-ing of impulses.

The Central Nervous System

When you make a call to a friend,your call travels through wires to acontrol center where it is switchedover to wires that connect with yourfriend’s telephone. In the same man-ner, an impulse traveling throughneurons in your body usually reachesthe control center of the nervous sys-tem—your brain—before beingrerouted. The brain and the spinalcord together make up the centralnervous system, which coordinatesall your body’s activities.

976

Figure 36.5Neurotransmittersare released into thesynaptic space by theaxon. When the neu-rotransmitters bindto receptors on thedendrites of the nextneuron, the ion chan-nels open, changingthe polarity of thedendrites. In thisway, nerve impulsesmove from neuron to neuron.

The myelin sheath gives axons awhite appearance. In the brain andspinal cord, masses of myelinatedaxons make up what is called “whitematter.” Has anyone ever told you to“use your gray matter”? They wereactually referring to a specific part ofyour brain. The absence of myelin inmasses of neurons accounts for thegrayish color of “gray matter” in thebrain.

Connections between neuronsAlthough neurons lie end to end—

axons to dendrites—they don’t actu-ally touch. A tiny space lies betweenone neuron’s axon and another neu-ron’s dendrites. This junction betweenneurons is called a synapse. Impulsestraveling to and from the brain mustmove across the synaptic space thatseparates the axon and dendrites.How do they make this leap?

As an impulse reaches the end of anaxon, calcium channels open, allow-ing calcium to enter the end of theaxon. As shown in Figure 36.5, thecalcium causes vesicles in the axon tofuse with the plasma membrane,releasing their chemicals into the

OriginWORDWORD

synapseFrom the Greekword synapsis,meaning “union orjoining.” A synapseis a junction thatconnects two neurons.

View an ani-mation of the synapsein the PresentationBuilder of the Inter-active CD-ROM.

CD-ROM

976


Spinal Cord InjuriesLinguistic Have studentsresearch the latest treatments

for spinal cord injuries and the progressscientists have made in stimulating nervecells to repair themselves. They shouldinclude a copy of their reports in theirjournals.

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Exploring MedicineLinguistic Have students interestedin medicine interview a doctor to

find out what type of preparation theyneed for medical school. L2

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Involuntary ActionsLinguistic Ask students to listactivities their bodies do without

conscious thought. To get them started,have them consider what their bodiesdo while they are asleep.

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P R O J E C TNeuroscience Research

Linguistic Have students researchand prepare a report, a visual device,

or an audiovisual presentation on one ofthe following topics: sleep, split brainexperiments, dementia, Alzheimer’s dis-ease, retrograde amnesia, or Penfieldmaps of the brain. Have students presenttheir findings to the class.

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VIDEODISCThe Infinite Voyage Fires of the Mind

Synaptic Development (Ch. 5)5 min. 30 sec.


Animation: Impulse TransmissionAcross a SynapseDisc 5

!7U`H"Biology: The Dynamics of LifeImpulse Transmission: Synapse(Ch. 38)Disc 2, Side 1, 38 sec.

!:|~"

ActivityHave students take a right/lefthemispheric mode indicator testto assess their personal approachto learning. Indicator tests areavailable from EXCEL INC, 200W. Station St., Barrington, IL60010.

Visual LearningFigure 36.5 Draw attention tothe illustration as you discuss thetransmission of an impulse acrossa synapse.

EnrichmentLinguistic Have interestedstudents read “Wide Hats

and Narrow Minds” (fromStephen Jay Gould’s The Panda’sThumb), which looks at the topicof brain size versus intelligence.L3

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Basic Concepts Transparency66 and Master

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VIDEODISCSTV: Human BodyVol. 2

Nervous SystemUnit 2, Side 2, 1 min. 59 sec.The Brain and Its Parts

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APE

Cerebrum

Cerebellum

Brain stem

Cerebral cortex

Cerebellum

Frontal lobeParietal lobe

Brain stemTemporal lobe

Occipital lobe

HUMAN

COMPLEX COORDINATIONThe cerebral cortex may look like a uniform mass of nerve tissue. But dif-ferent areas of the cortex receive and process different types of sensory,motor, and integrative nerve impulses. Using a technological tool known as aPET (positron emission tomography) scan (above left), scientists can pin-point areas of increased metabolic activity in the brain. In so doing they canidentify specific regions of the cortex that are involved in complex behaviorssuch as playing—from memory—a musical composition on the violin.

THE HUMAN BRAINThe largest part of the human brain is the cerebrum. The cerebrum is divid-ed into two hemispheres, left and right. But the feature that makes the cere-brum unique is an outer, folded layer less than 5 mm thick—the cerebralcortex. Because of the cortex, you can remember, reason, organize, commu-nicate, understand, and create.

When you watch an Olympic gymnast perform on the balance beam, you arewitnessing the work of a well-trained cerebellum. It is here that muscles arecoordinated and the memories of physical skills are stored.

The brain stem consists of the medulla, pons, and midbrain. The brain stemregulates breathing, heart rate, circulation, and other vital body processes.

DOG

Cerebrum

Cerebellum

EXPANDING Your View

1 THINKING CRITICALLY Fish, reptiles, and dogs rely far more ontheir sense of smell to monitor their environments than humans do.How do the brain structures of these different animals reflect this fact?

2 JOURNAL WRITING In your journal, record your predictions about howa person’s behavior might be affected by an injury to the cerebellum.

Olfactory bulb

Brain stem

GIRL PLAYING A VIOLIN

PET SCAN

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EnrichmentHave students research the workof evolutionary biologists such asNiles Eldridge and Stephen JayGould. What facts are they ableto base their work on? Howmuch do they have to infer fromfossil and other records?

Visual LearningVisual-Spatial Display mod-els or posters of various ver-

tebrate brains. Point out thedifferences among the brains.

Tying to PreviousKnowledgeReview the evolutionary se-quence of the various phyla, pay-ing special attention to the evolu-tionary tree of the vertebrates.

Answers to Expanding Your View

1. The percentage of braindevoted to the sense of smellis much larger in these ani-mals than in the humanbrain.

2. The cerebellum coordinatesphysical skills, such as walk-ing. Damage to this area ofthe brain could cause a per-son to have jerky, uncoordi-nated movements.

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Cerebrum

FISH

Olfactory bulb

THE EVOLVING BRAIN Jumping ahead millions of years towhen the vertebrates emerged, thefive brains shown here illustratehow evolution has transformed asimple ganglion to a complex brain.As the brain evolved, areas thatcontrol senses, behavior, and coor-dination became predominant.

Notice that in humans the brainis proportionally much larger than itis in many other vertebrates andthat the area dedicated to thinking,the cerebrum, covers and domi-nates everything else.

As animals have evolved overhundreds of millions of years,there has been a tendencytoward ever-increasing com-plexity in the nervous system,and especially, in the brain.Brains had their beginnings asrelatively simple bundles ofnerve cells. But over time, thebrains of vertebrate animalshave become more complex andspecialized. Humans possess themost complex brain in the animal kingdom, a remarkableorgan that enables us to reason, wonder, and dream.

of the

THE SIMPLEST BRAINFlatworms are the simplestanimals that have an identifi-able brain. A planarian, forexample, has a mass of nervetissue called a ganglion thatlies beneath each eyespot.Extending back from theseganglia are long nerve cordsthat run the length of thebody. Between the cords arecross connections that makethe planarian nervous systemlook like a ladder.

LIZARD

OLYMPIC GYMNAST

Brain stem

EvolutionBrain

FOCUSON

PLANARIAN

Nerve cords

Ganglion

Cerebrum

Brain stem

Cerebellum

Olfactory bulb

Cerebellum

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Focus OnEvolution of the Brain

PurposeStudents will explore the evolu-tion of the brain by comparingthe brains of different animals.They will also learn about brainstructure and function.

BackgroundFunctionally, the human braincan be divided into the lobes ofthe cerebrum (including the cere-bral cortex), the cerebellum, andthe brain stem—pons, midbrain,and medulla oblongata.

Over the course of humanevolution, the human brain hastripled in size. Scientists surmisethat the increase in brain sizeaccompanied the developed useof tools and other skills thatenabled our ancestors to live in agreater variety of habitats.

Teaching Strategies■ Have students in groups drawa large outline of the brain on apiece of poster paper. Have themcut out magazine pictures thatrelate to the specializations of thebrain and glue them on their out-line. For instance, they could cutout eyes and place them in theoccipital lobe to indicate that iswhere vision is interpreted. ■ Have students make scalemodels of the cerebrums in thedifferent animals shown. Thenhave them compare the size ofthe cerebrum with the size of theanimal. Which animal has thelargest cerebrum for its bodysize? Which has the smallest?

Going FurtherGoing Further

Students interested in the evo-lution and function of the braincan read Dragons of Eden, byCarl Sagan.


BioLab and MiniLab Work-sheets, p. 159 L2

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VIDEODISCThe Infinite VoyageFires of the Mind, The Brain and

Memory (Ch. 6), 6 min.

The Brain: Understanding Left and Right(Ch. 8), 6 min.

The Brain and Defining Our Talents (Ch. 9) 9 min. 30 sec.!7_jJ"

!7s~D"

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VIDEODISCThe Infinite Voyage Unseen WorldsMagnetic Resonance Imaging:

MRI a Medical Breakthrough (Ch. 6) 2 min. 30 sec.

Unseen WorldsBrain Tumor Surgery: Made Possible by MRI(Ch. 7) 2 min. 30 sec.

!7_jJ" !7itB"

Motorneuron

Interneuron

Spinalcord

Flexor muscle contracts and withdraws part being stimulated

Sensory neuron

Direction of impulse

Pain receptors in skin

to pound. Your breathing becomesrapid. Your thoughts race wildly asyou try to figure out what to do—stay and confront the unknown, orrun out of the house!

Your internal reactions to thisscary situation are being controlledby your autonomic nervous system.The autonomic nervous systemcarries impulses from the CNS tointernal organs. These impulses pro-duce responses that are involuntary,or not under conscious control.

There are two divisions of theautonomic nervous system—thesympathetic nervous system andthe parasympathetic nervous system.The sympathetic nervous systemcontrols many internal functions dur-ing times of stress. When you arefrightened, the sympathetic nervoussystem causes the release of a hor-mone that results in the fight-or-flight response you learned aboutearlier, as shown in Figure 36.8.

The parasympathetic nervoussystem on the other hand, controlsmany of the body’s internal functions

when it is at rest. Itis in control when youare relaxing on a warmsummer day after a picnic orreading quietly in your room.Both the sympathetic andparasympathetic systems send signalsto the same internal organs. Theresulting activity of the organdepends on the intensities of theopposing signals.


Figure 36.8A fight-or-flightresponse to a rattlesnake willincrease heart andbreathing rates.

Figure 36.7A simple refleximpulse involves onesensory neuron, oneinterneuron, and onemotor neuron.

Concept DevelopmentHave students name some of thereflexes an infant has from birth.List these reflexes on the chalk-board. Ask students how thesebehaviors are different from con-scious behaviors such as walkingand talking. Reflexes are not learnedbehaviors.

paper clip farther apart until your part-ner can feel two points rather than one.

4. Determine the distance between sen-sory neurons in a certain body area bymeasuring the distance between thetwo ends of the paper clip.

5. In a data table, record the distancebetween sensory neurons in differentparts of the body.

Analysis1. Which areas of the skin did you find

most sensitive? Least sensitive?Responses will vary depending uponthe areas tested. Regions of the backand inner arms will be less sensitivethan areas of the palms and fingers.

2. Explain why two stimuli are felt as twopoints when the ends of the paper clipare moved farther apart. The two sig-nals are detected by different sensoryneurons.

Portfolio Have students include asummary of the lab, the data table, andanswers to Analysis questions in theirportfolios. Have them also write a para-graph explaining possible advantages ofsome areas of the skin being more sensi-tive than others. Use the PerformanceTask Assessment List for Lab Report inPASC, p. 47. PP

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Distractions and Reaction TimeHave you ever tried to read whilesomeone is talking to you? Whateffect does such a distracting stimulushave on your reaction time?

Procedure! Work with a partner. Sit facing

your partner as he or she stands.@ Have your partner hold the top of

a meterstick above your hand.Hold your thumb and index fingerabout 2.5 cm away from either sideof the lower end of the meterstick without touching it.

# Tell your partner to drop the meterstick straight downbetween your fingers.

$ Catch the meterstick between your thumb and finger assoon as it begins to fall. Measure how far it falls beforeyou catch it. Practice several times.

% Run ten trials, recording the number of centimeters themeterstick drops each time. Average the results.

^ Repeat the experiment, this time counting backwardsfrom 100 by fives (100, 95, 90, . . .) as you wait for yourpartner to release the meterstick.

Analysis1. Did your reaction time improve with practice? Explain.2. How was your reaction time affected by the distraction

(counting backward)?3. What other factors, besides distractions, would increase

reaction time?

MiniLab 36-1MiniLab 36-1 Experimenting

The Peripheral Nervous System

Remember that the peripheral ner-vous system carries impulses betweenthe body and the central nervous sys-tem. For example, when a stimulus ispicked up by receptors in your skin,it initiates an impulse in the sensoryneurons. The impulse is carried tothe CNS. There, the impulse trans-fers to motor neurons that carry theimpulse to a muscle.

The peripheral nervous system canbe separated into two divisions—the

somatic nervous system and the auto-nomic nervous system.

The somatic nervous systemThe somatic nervous system is

made up of 12 pairs of cranial nervesfrom the brain, 31 pairs of spinalnerves from the spinal cord, and allof their branches. These nerves areactually bundles of neuron axonsbound together by connective tissue.The cell bodies of the neurons arefound in clusters along the spinal col-umn. Most nerves contain both sen-sory and motor axons.

The nerves of the somatic systemrelay information mainly betweenyour skin, the CNS, and skeletalmuscles. This pathway is voluntary,meaning that you can decide whetheror not to move body parts under thecontrol of this system. Try theMiniLab on this page to find out howdistractions can affect the time ittakes you to respond to a stimulus.

Reflexes in the somatic systemSometimes a stimulus results in an

automatic, unconscious responsewithin the somatic system. Whenyou touch something hot, you auto-matically jerk your hand away. Suchan action is a reflex, an automaticresponse to a stimulus. Rather thanproceeding to the brain for interpre-tation, a reflex impulse travels to thespinal column where it is sentdirectly back out to a muscle. Thebrain becomes aware of the reflexonly after it occurs. Figure 36.7 onthe next page shows the shortenedroute of a reflex impulse.

The autonomic nervous systemImagine that you are spending

the night alone in a creepy oldhouse. Suddenly, a creak comesfrom the attic and you think youhear footsteps. Your heart begins


Purpose Students investigate how a dis-tracting stimulus affects reactiontime.

Process Skillsobserve and infer, compare andcontrast, recognize cause andeffect, collect and organize data,interpret data, experiment, ana-lyze

Teaching Strategies■ If students find counting back-wards awkward, have them whis-tle or sing a song as another kindof distraction.

Expected ResultsA distraction should increasereaction time.

Analysis1. As students learn to antici-

pate the drop, their reactiontime should improve.

2. The distraction probablyincreased their reaction time.

3. Answers may include beingtired, sick, hungry, or other-wise preoccupied.

Skill Have students de-scribe the sequence of eventsinvolved in their response to thefalling meterstick. They shouldidentify the stimulus (seeing thefalling stick), the path of theimpulse in their bodies, and theeffect (grabbing the stick). Usethe Performance Task AssessmentList for Events Chain in PASC,p. 91. L2

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Alternative LabSkin Sensitivity

Purpose Students design and carry out an experi-ment to determine the sensitivity of theirskin.

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Materialspaper clips unfolded in U-shapes, metricrulerBackgroundCertain areas of the skin contain sensoryneurons that are packed closely together,whereas other areas have neurons scat-tered up to centimeters apart. When twodifferent stimuli depolarize parts of thesame neuron, the brain interprets them asif they were one stimulus.

ProcedureGive students the following directions.

1. Working with a partner, plan ten areasof the skin to test for the distancebetween sensory neurons.

2. Have your partner close his or her eyes.With the paper clip ends closetogether, test your partner by gentlytouching his or her skin with theopened paper clip.

3. Continually spread the two ends of the980

MiniLab 36-1MiniLab 36-1


Kinesthetic Demonstratethe knee-jerk reflex using

a rubber hammer. Point outthat students did not choose tomove their legs—they did soautomatically.

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3 AssessCheck for UnderstandingMake sure students understandthat some parts of the nervoussystem are not under consciouscontrol. Test their understandingby asking students to list bodyfunctions that they can and can-not control. Have them identifythe part of the brain that controlseach function. L2

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CentralNervousSystem(CNS)

SomaticNervousSystem

(voluntary)

Relays informationto and from skin and

skeletal muscles.

AutonomicNervousSystem

(involuntary)

Relays informationto internal organs.

Sympathetic NervousSystem

Controls organs in times of stress.

Parasympathetic NervousSystem

Controls organs when body is at rest.

PeripheralNervousSystem(PNS)

Nervous System

Section AssessmentSection Assessment

Understanding Main Ideas1. Summarize the charge distribution that exists

inside and outside a resting neuron.2. Outline the functions of the three major parts

of the brain.3. Contrast the functions of the two divisions of

the autonomic nervous system.4. How does the Na+/K+ pump affect ion distribu-

tion in a neuron?

Thinking Critically5. Why is it nearly impossible to stop a reflex from

taking place?

6. Sequencing Sequence the events as a nerveimpulse moves from one neuron to another. Formore help, refer to Organizing Information inthe Skill Handbook.

SKILL REVIEWSKILL REVIEW

Figure 36.9Understanding theorganization of yournervous system canbe made easier bystudying the differ-ent divisions of thenervous system.

The different divisions and subsys-tems of your nervous system aresummarized in Figure 36.9. Eachdivision plays a key role in communi-cation and control within your body.

Note that the sympathetic and

parasympathetic systems are part of theautonomic nervous system. The auto-nomic and somatic systems are part ofthe peripheral nervous system. Theperipheral nervous system feeds infor-mation to the central nervous system.


ReteachHave students make a table thatlists the three major parts of thebrain and the functions of each.

ExtensionHave interested students find outabout the function of variousneurotransmitters such as dopa-mine, serotonin, norepinephrine,adenosine, or GABA.

Skill Prepare a handoutshowing a resting neuron, a stim-ulated neuron, and a synapse.Have students label the steps ofneurotransmission.

4 CloseDiscussionAsk students what would happenif their cerebellum were dam-aged. For example, could theyplay a video game? probably not,because the cerebellum controls coor-dination

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Reinforcement and StudyGuide, pp. 159-160

Content Mastery, p. 178Basic Concepts Transparency

67 and Master

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Section AssessmentSection AssessmentSection Assessment1. The inside of the neuron is more nega-

tively charged than the outside.2. The cerebrum controls conscious activi-

ties, intelligence, memory, language,movement, and the senses. The cerebel-lum controls balance, posture, and co-ordination. The medulla oblongatamainly controls involuntary activities.

3. The sympathetic nervous system con-trols functions in times of stress, whilethe parasympathetic controls functionswhile the body is at rest.

4. The pump moves three sodium ionsout of the cell for every two potassiumions it pumps into the cell.

5. A reflex is an involuntary action thatdoes not involve conscious control by

the brain. You cannot stop it.6. An impulse reaches the end of an

axon, opening calcium channels. Thiscauses vesicles to fuse with the mem-brane and release their chemicals.These chemicals diffuse across thesynaptic space to the dendrites of thenext neuron.

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Olfactory nerve

Smell moleculesTaste molecules

Olfactory bulb

Olfactory nerve receptors

Taste bud

Sensory neuron

Section

Picture yourself in a park on a beautiful summer day.Stretching out on the grass,

you look up and see white cloudsfloat by against a background ofblue. You feel grass tickling yourtoes and hear a breeze rustling the leaves of the trees. Sipping on a glass of lemonade, you noteits tangy odor and sweet flavor.All these sensations are made possible by your senses: sight,touch, hearing, smell, andtaste. Senses enable you to interpret your environment.

SECTION PREVIEW

ObjectivesDefine the role of thesenses in the humannervous system.Recognize how senses detect chemical,light, and mechanicalstimulation.Identify ways in which the senses worktogether to gatherinformation.

Vocabularytaste budretinarodsconescochleasemicircular canals

36.2 The Senses

Figure 36.10Chemicals stimulateboth smell and tastereceptors.

Taste buds (inset) respondto different chemical stimuli.

Sensing ChemicalsHow are you able to smell and

taste the lemonade? Chemical mole-cules of lemonade contact receptorsin your nose and mouth as you sniffand drink the beverage. The recep-tors for smell are hairlike nerve end-ings located in the upper portion ofyour nose, as shown in Figure 36.10.Chemicals acting on these nerve end-ings initiate impulses in the olfactorynerve, which is connected to yourbrain. In the brain, this signal isinterpreted as a particular odor.

The senses of taste and smell areclosely linked. Think about whatyour sense of taste is like when yournose is stuffed up and you can smell

Magnification:1040�

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Section 36.2

PrepareKey ConceptsThe anatomy and physiology ofthe major senses are presented.The senses that detect chemicals(taste, smell), the sense thatdetects light (vision), and thesenses that detect mechanicalstimulation (hearing, touch, andbalance) are examined.

Planning■ Make or purchase a tape of

common sounds for the firstQuick Demo.

■ Acquire models of ears, eyes,skin, and nose for the Display.

■ Order cow or sheep eyes forthe Inside Story.


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List the senses that you think the person in this scene is using.

Identify the stimulus for each of the senses you listed in question 1.

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P R O J E C TModeling the Senses

Kinesthetic Have student groupsselect and make a model of one of

the senses. The model may demonstratethe anatomy or the function of the sense.Have students explain and demonstratetheir models to the class.

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VIDEODISCThe Infinite Voyage A Taste ofHealth, Developing Taste (Ch. 3)

7 min. 30 sec.

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Lens

Retina

Optic nerve

Visual cortexin cerebrum

36.2 THE SENSES 985

The Eye

The light energy that reaches your retina is convertedinto nerve impulses, which are interpreted by your

brain, allowing you to see the world around you.

Critical Thinking How would a person’s vision beaffected if his or her rod cells didn’t function?

Rod and cone cells

INSIDESSTORTORYY

INSIDE

Rod and cone cells Rod cells in the retina are excited by low levels of light. These cellsconvert light signals into nerve impulses andrelay them to the brain. Your brain interpretsthe information as a black and white picture.Your cone cells respond to bright light. Theyprovide the brain with information about color.

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Visual field Close one eye. Everything youcan see with one eye open is the visual field of that eye. The visual field of each eye can bedivided into two parts: a lateral and a medialpart. As shown, the lateral half of the visualfield projects onto the medial portion of theretina, and the medial half of the visual fieldprojects onto the lateral portion of the retina.

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Brain image projections The right halfof the retina in each eye is connected tothe right side of the visual cortex in thecerebrum. The left half of the retina is simi-larly connected to the left side of the visualcortex. Thus images entering the eye fromthe right half of each visual field project tothe left half of the brain, and vice versa.

44 Depth perception The visualfields of the eyes partially overlap,each eye seeing about two-thirdsof the total field. This overlapallows your brain to judge thedepth of your visual field.

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IINSIDENSIDESSTORTORYY

INSIDE

Purpose Students examine the functionand structure of rods and conesand the divided projection of thevisual field.

Teaching Strategies■ Ask students which cells aremost active when they are read-ing color comics. cone cells■ Have students close one eye ata time and note the visual fieldthey see out of each.■ Ask students to explain howthey are able to judge depthsusing both eyes together.

Visual Learning■ Dissect a cow or sheep eye.

Cow and sheep eyes have alayer on the inner choroid coatthat is not present in humans.Explain that this iridescentlayer enhances night vision byreflecting some light back intothe retina.

Critical ThinkingBecause rod cells function in lowlevels of light, the person wouldbe virtually blind in dimly litareas.

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Optic disk(blind spot)

Fovea

Retina

ChoroidSclera

Optic nerve Vitreous humor

Aqueous humor

Light

Cornea

Pupil

Lens

Iris

little, if anything. Because much ofwhat you taste depends on your senseof smell, your sense of taste may alsobe dulled. You taste something whenchemicals dissolved in saliva contactsensory receptors on your tonguecalled taste buds. Signals from yourtaste buds travel to the cerebrum.There, the signal is interpreted, andyou notice a particular taste.

Tastes that you experience can bedivided into four basic categories: sour,salty, bitter, and sweet. Certain regionsof your tongue react more stronglyto particular categories. Bitter flavorsare most likely to be sensed at theback of the tongue, sour on the sides,and sweet and salty on the tip.

Sensing LightHow are you able to see? Your sense

of sight depends on receptors in youreyes that respond to light energy. Theretina, found at the back of the eye,is a thin layer of tissue made up oflight receptors and sensory neurons.

Light enters the eye through thepupil and is focused by the lens ontothe back of the eye, where it strikesthe retina. Follow the pathway oflight to the retina in Figure 36.11.

The retina contains two types oflight receptor cells—rods and cones.Rods are receptor cells adapted forvision in dim light. They help youdetect shape and movement. Conesare receptor cells adapted for sharpvision in bright light. They also helpyou detect color.

At the back of the eye, retinal tis-sue comes together to form the opticnerve, which leads to the brain,where images are interpreted. Canyou see as well with one eye as withtwo? To find out more about how thebrain forms a visual image, read theInside Story.

Sensing MechanicalStimulation

How are you able to hear the leavesrustle and feel the grass as you relaxin the park? These senses—hearingand touch—depend on receptors thatrespond to mechanical stimulation.

Your sense of hearingEvery sound causes the air around

it to vibrate. These vibrations traveloutward from the source in waves,called sound waves. Sound wavesenter your outer ear and travel downto the end of the ear canal, wherethey strike a membrane called theeardrum and cause it to vibrate. Thevibrations then pass to three smallbones in the middle ear—themalleus, the incus, and the stapes. Asthe stapes vibrates, it causes fluid inthe cochlea, a snail-shaped structurein the inner ear, to move like a waveagainst the hair cells that line thecochlea’s circular walls. Pressed bythe fluid, the hairs bend.


Figure 36.11A cross section through the human eye shows thepath light takes as it enters through the pupil.

OriginWORDWORD

retinaFrom the Latinword rete, meaning“net.” The retinacontains a networkof light-sensitivecells.

View anima-tions of the eye andear located in thePresentation Builderof the InteractiveCD-ROM.

CD-ROM

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2 Teach

Concept DevelopmentAsk students what kind of infor-mation the sense organs keep thebody informed of. They inform thebody of changes that occur in the sur-roundings. What is the reason forkeeping the body informed? Sothat it can respond to changes in theenvironment.

EnrichmentInvite an audiologist tospeak to the class about

sound levels, how they are mea-sured, and damage that mayresult from high levels. Have theaudiologist demonstrate howhearing is tested.

DisplayVisual-Spatial Obtain dis-play models of the ear, eye,

skin, or nose. Have studentsexamine the models as they readabout each sense.

Knowledge Have studentswrite two questions about thesense of sight. Students shouldask these questions of a classmateand then exchange questions withhim or her. L2

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Auditory-Musical Toshow how important

each sense is, play a tape ofvarious common sounds thatstudents can identify. Discussthe dependence of humanson senses and the adjustmentsthat are made if one sense islost.

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Comparing Eyes to CamerasLinguistic Ask students to write anessay comparing the eye to a cam-

era. They should include references to thelens, the aperture, the body, and the shut-ter of the camera. Review the function ofthese camera parts with students.Students should include a copy of theessay in their journals.

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PortfolioPortfolio

Creating a FlowchartVisual-Spatial Have students useFigures 36.11 and 36.12 to create

flowcharts that show the series of eventsinvolved in seeing an object or hearing asound. Encourage students to include thenames of the eye, ear, and brain partsinvolved in these processes.

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CD-ROMBiology: The Dynamics of LifeAnimation: The Sense of Sight

Disc 5

VIDEODISCBiology: The Dynamics of LifeSense of Sight (Ch. 39)

Disc 2, Side 1, 30 sec.

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Section Focus Transparency 88and Master


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Maintaining balance is the functionof your semicircular canals. Like thecochlea, the semicircular canals arealso filled with a thick fluid and linedwith hair cells. When you tilt yourhead, the fluid moves, causing thehairs to bend. This movement stimu-lates the hair cells to produce im-pulses. Neurons carry the impulses tothe brain, which sends an impulse tostimulate your neck muscles andreadjust the position of your head.

Your sense of touchLike the ear, your skin also

responds to mechanical stimulationwith receptors that convert the stim-ulus into a nerve impulse. Receptorsin the dermis of the skin respond tochanges in temperature, pressure,and pain. It is with the help of thesereceptors, shown in Figure 36.13,that your body is able to respond toits external environment.

Although some receptors arefound all over your body, thoseresponsible for responding to partic-ular stimuli are usually concentratedwithin certain areas of your body. Forexample, receptors that respond tolight pressure are numerous in thedermis of your fingertips, eyelids,lips, the tip of your tongue, and thepalms of your hands. When thesereceptors are stimulated, you per-ceive sensations of light touch.

Receptors that respond to heavierpressure are found inside your joints,in muscle tissue, and in certainorgans. They are also abundant onthe skin of your palms and fingersand on the soles of your feet. Whenthese receptors are stimulated, youperceive heavy pressure.

Free nerve endings extend into thelower layers of the epidermis. Thesenerve endings act as pain receptors.You have two other kinds of receptorsthat respond to temperature. Heatreceptors are found deep in the der-mis, while cold receptors are foundcloser to the surface of your skin.

36.2 THE SENSES 987

Hairshaft

Free nerveending (pain)

Heat

Heavypressure

Cold

Lighttouch

Opening ofsweat gland

Figure 36.13Many kinds of recep-tors are locatedthroughout the dermis of your skin.Some receptorsdetect gentletouches; othersrespond to heavypressure. The sensa-tions of pain, heat,and cold are sensedby other kinds ofreceptors.


Understanding Main Ideas1. Summarize the types of messages the senses

receive.2. When you have a cold, why is it hard to taste

food?3. Explain how your eyes detect light and

images.4. What types of receptors are found in the

skin?

Thinking Critically5. Why might an ear infection lead to problems

with balance?

6. Sequencing List the sequence of structuresthrough which sound waves pass to reach theauditory nerve. For more help, refer toOrganizing Information in the Skill Handbook.


3 AssessCheck for Understanding

Visual-Spatial Have studentslabel diagrams of the eye,

ear, and nose.

ExtensionHave students research andreport on the causes and treat-ments of cataracts, glaucoma, orvertigo.

Knowledge Provide stu-dents with a list of sensations(such as pain, pressure, cold, odor,and so on) that can be detected bythe body. Have them match eachsensation with the sense organthat detects it.

4 CloseDiscussionAsk students to identify which ofthe following professions couldbe undertaken by someone whohas lost the sense of sight: archi-tect, violinist, mathematician,public speaker, professional ath-lete, accountant, physicist. Whatspecial tools (e.g., talking com-puters) would someone withoutsight have to use for each of theprofessions listed?

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Section AssessmentSection AssessmentSection Assessment1. The eyes respond to light. The ears re-

spond to sound. Touch receptors respondto mechanical stimulation. The tongueand nose respond to chemicals.

2. The tasting of food involves both thesense of smell and the sense of taste.

3. Light stimulates the rod or cone cells inthe retina, which transmit a signal to thebrain by way of the optic nerve.

4. touch, temperature, pressure, and pain5. Swelling associated with an ear infection

could cause fluid in the ear to put pres-sure on the semicircular canals and causethe hairs in the canals to signal a falsesense of balance in the brain.

6. outer ear, eardrum, malleus, incus, andstapes, fluid of cochlea, hairs of cochlea,auditory nerve to the brain

Fluid

FluidFluid

Cochlearduct

Auditorynerve

Inner ear

Outer ear Middle ear

The movement of the hairs pro-duces electrical impulses, which travelalong the auditory nerve to the sidesof the cerebrum, where they are inter-preted as sound. Trace the pathway ofsound waves in Figure 36.12. To findout what impact loud sounds have onyour hearing, do the Problem-SolvingLab on this page.

Your sense of balanceThe inner ear also converts infor-

mation about the position of yourhead into nerve impulses which travelto your brain, informing it aboutyour body’s equilibrium.


Hair cells

Sensory neurons

Figure 36.12The internal structureof the human ear isdivided into threeareas: the outer ear,middle ear, and innerear. Follow the path-way sound wavestake as they movethrough your ear.

When are loud sounds dangerous to our hearing? Obser-vations may be described as either qualitative or quantitative.A qualitative observation about a woman’s height might bethat she is tall. A quantitative observation about the sameperson might be that she is 1.92 m tall.

Analysis“Hearing loss afflicts approximately 28 million people in

the United States. Approximately 10 million of these impair-ments may be partially attributable to damage from exposureto loud sounds. Sounds that are sufficiently loud to damagesensitive inner ear structures can produce hearing loss that is not reversible. Very loud sounds of short duration, such asan explosion or gunfire, can produce immediate, severe, andpermanent loss of hearing. Longer exposure to less intensebut still hazardous sounds encountered in the workplace orduring leisure activities, exacts a gradual toll on hearing sensitivity, initially without the victim’s awareness. Live orrecorded high-volume music, lawn-care equipment, and airplanes are examples of potentially hazardous noise.”

“Noise and Hearing Loss,” NIH Consensus Statement,January 22-24, 1990.

Thinking Critically1. Choose and record two sentences or phrases from the

passage above that provide examples of quantitativeobservations. Explain your selections.

2. Choose and record two sentences or phrases that provide examples of qualitative observations. Explain your selections.

3. Choose and record one sentence or phrase that providesan example of an inference. Explain your selection.

4. Suggest ways to minimize the type of noise exposure discussed in the last sentence.

Problem-Solving Lab 36-1Problem-Solving Lab 36-1 Interpreting andAnalyzing

Sounds waves strike a mem-brane called the eardrumand cause it to vibrate.

AA

Impulses travel along the auditorynerve to the sides of the cerebrum,and you hear the sound.

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Cochlea

Ovalwindow

Semicircularcanals

Ear canal

Ear drum

MalleusIncus

Stapes

Fluid in thecochlea thenpicks up thevibrations andmoves like awave againstthe hair cells.

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The vibrations are passed on to threebones in the middle ear–the malleus,the incus, and the stapes.

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Purpose Students gain practice in deter-mining whether statements areobservations or inferences.

Process Skillsacquire information, define oper-ationally, observe and infer, rec-ognize cause and effect, thinkcritically

Teaching Strategies■ Refer students to the“Observing and Inferring” sec-tion in the Skill Handbook at theback of this text. The entirereport can also be accessed on theInternet.

Thinking Critically

1. Student choices must includea specific number. A defini-tion of the word quantitativeshould also be included intheir answer.

2. Student choices should notinclude a specific number. Adefinition of the word quali-tative should also be included.

3. Student may cite sentencesthat include “may be” or“can.” A definition of theword inference should also beincluded in their answer.

4. Student answers may includethe wearing of protectivehearing devices and reducingvolume or exposure time.

Portfolio Ask students toresearch the meaning of the termdecibel and then prepare a posterlisting noise-causing agents andtheir decibel ratings. Have themplace the posters in their portfo-lios. Use the Performance TaskAssessment List for Poster inPASC, p. 73. L2

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Problem-Solving Lab 36-1Problem-Solving Lab 36-1


Hearing Impaired/VisuallyImpairedStudents who are hearing or visually impaired may be sensitive during discus-sions of the senses. Be prepared toanswer questions about the causes andpossible treatments of hearing or visualimpairment.

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CD-ROM Biology: The Dynamics of Life, Animation: The Sense ofHearing, Disc 5VIDEODISC Biology: The Dynamics of Life Sense of Hearing (Ch. 40)

Disc 2, Side 1, 1 min.!;,Ç"


Reinforcement and StudyGuide, p. 161

Content Mastery, p. 179Concept Mapping, p. 36


Reteaching Skills Trans-parencies 52, 53 andMasters

Laboratory Manual, pp. 265-268 L2

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Figure 36.15Sticky sap from thefruit of an opiumpoppy is used tomake drugs calledopiates.

Problem-Solving Lab 36-2Problem-Solving Lab 36-2 Formulating ModelsMedicinal Uses of Drugs

A medicine is a drug that, whentaken into the body, helps prevent,cure, or relieve a medical problem.Some of the many kinds of medicinesused to relieve medical conditions arediscussed below.

Relieving painHeadache, muscle ache, cramps—

all are common pain sensations. Youjust studied how pain receptors inyour body send signals to your brain.Medicines that relieve pain manipu-late either the receptors that initiatethe impulses or the central nervoussystem that receives them.

Pain relievers that do not cause aloss of consciousness are called anal-gesics. Some analgesics, like aspirin,work by inhibiting receptors at thesite of pain from producing nerveimpulses. Analgesics that work on thecentral nervous system are callednarcotics. Many narcotics are madefrom the opium poppy flower, shownin Figure 36.15. Opiates, as they arecalled, can be useful in controlledmedical therapy because only thesedrugs are able to relieve severe pain.

36.3 THE EFFECTS OF DRUGS 989

How do different drugs affect the levels of neurotrans-mitters in synapses? Drugs can act on neurotransmitters ina number of different ways. For example, they may speed upthe reabsorption of a neurotransmitter back into the den-drite end of a neuron. Or, they may block the release of theneurotransmitter from the axon end of a neuron. They mayalso prevent the breakdown of the neurotransmitter byblocking the enzyme responsible for this action.

Analysis Examine the

diagram shown here, which illus-trates how neu-rotransmitters work.

Thinking Critically 1. Design three different drugs:

a. One that will block the enzyme from breaking downthe neurotransmitter.

b. One that will prevent the neurotransmitter from reach-ing the receptor site on the dendrite.

c. One that will block the release of the neurotransmitterfrom the axon.

2. Draw three separate figures to show how each of yourdrugs works.

3. Predict the effects of each drug on the body. Explain youranswer.

Axon

Dendrite

Enzyme Neurotransmitter

Purpose Students design drugs that willinterfere with the action of neu-rotransmitters.

Process Skillsapply concepts, formulate mod-els, hypothesize, interpret scien-tific illustrations, predict,recognize cause and effect, thinkcritically

Teaching Strategies■ Review the nature of thesynapse and how neurotransmit-ters work normally.■ Encourage students to con-sider the shapes of the neuro-transmitter molecules, enzymes,and binding sites when designingtheir blockers.■ Allow students to work insmall groups.

Thinking Critically

1. Student models will vary.Make sure that each one pro-duces the effect described.

2. Student figures should indi-cate how each of their drugsworks.

3. (a) Message will be transmit-ted for a longer period of timethan normal; (b) Message willnot be received by dendrite;(c) Message will not be deliv-ered to dendrite.

Knowledge Ask studentsto make a diagram showing sometype of neurotransmitter block-age. Ask them to interpret thedrawing. Use the PerformanceTask Assessment List for ScientificDrawing in PASC, p. 55. L2

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Problem-Solving Lab 36-2Problem-Solving Lab 36-2Section

Drugs Act on the BodyYou probably hear the word drug

used often, maybe even every day. Adrug is a chemical that affects thebody’s functions. Most drugs interactwith receptor sites on cells, probably

the same ones used by neurotrans-mitters of the nervous system or hor-mones of the endocrine system.Some drugs increase the rate atwhich neurotransmitters are synthe-sized and released, or slow the rate atwhich they are broken down, as illus-

trated in Figure36.14. Otherdrugs interferewith a neuro-t r a n s m i t t e r ’sability to interactwith its receptor.Explore howthese differentdrugs work onneurotransmit-ters by doing theProblem-SolvingLab on the nextpage.

Nerves frazzled? Feeling tense? For aperson trying to quit a smoking habit,the desire for a cigarette is almost

overpowering. Without the person realizingit, an occasional cigarette has grown into apack-a-day habit. The body now cries out fornicotine. Why do people start smokingeven though nicotine is so addictive?

SECTION PREVIEW

ObjectivesRecognize the medici-nal uses of drugs.Identify the differentclasses of drugs.Interpret the effect ofdrug misuse and abuseon the body.

Vocabularydrugnarcoticstimulantdepressantaddictiontolerancewithdrawalhallucinogen

36.3 The Effectsof Drugs

Figure 36.14Drugs can increaseneurotransmitter lev-els in the synapse bystimulating their syn-thesis, increasingtheir release, or byslowing their break-down by enzymes.

Cigarettes, made fromtobacco leaves (top), containthe addictive drug nicotine.

Synaptic space

Increasedrelease

Decreasedenzymaticbreakdown

Dendrite

AxonIncreasedsynthesis


988

Section 36.3

PrepareKey ConceptsThis section summarizes themedicinal uses of drugs andexplains how addictive drugsaffect the body. The major classesof misused and abused drugs arediscussed.

Planning■ Bring in various nonprescrip-

tion drugs for students tocompare in the first QuickDemo.

■ Have students bring in maga-zines for the third BiologyJournal activity.

■ Order Daphnia and purchasecoffee, tea, cola, unfiltered cig-arettes, and cough syrup withdextromethorphen hydrobro-mide for the BioLab.


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Examine the diagram showing products obtained fromopium poppies. Which ones have you heard of?

Do you think it would be advisable to ban the growthof opium poppies? Explain.

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Transparency A Questionof Poppies89

Opium poppy

Morphineused to treatsevere pain

Heroinaddictive narcotic,no accepted medical use

Codeineused to treat painand cough

Papaverineused to treat heartdisease

Noscopineused to treat cough

Thebainedangerous narcotic,no acceptable medical use

Poppysap OpiumDry


English Language LearnersVisual-Spatial Have students withlimited English proficiency make a

poster that summarizes the effects ondifferent body systems of one drug thatis misused or abused. Have studentscombine their posters to create a bul-letin board display.

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Note Internet addressesthat you find useful in

the space below for quick reference.

Resource ManagerResource ManagerSection Focus Transparency 89 and

Master

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VIDEODISCThe Infinite Voyage Prisonersof the Brain: Neurotransmit-

ters and the Chemical Basis of MentalIllness (Ch. 3), 3 min.

Dopamine and Antipsychotic Drugs(Ch. 4), 7 min.

Using PCP to Study Schizophrenia(Ch. 5), 7 min. 30 sec.!7ALD"

!7KVF"

!7U`H" 989

Interpret a Drug Label One common misuse of drugs is notfollowing the instructions that accompany them. Over-the-counter medicines can be harmful—even fatal—if they arenot used as directed. The Food and Drug Administrationrequires that certain information about a drug be providedon its label to help the consumer use the medicine properlyand safely.

Procedure! The photograph below shows a label from an over-the-

counter drug. Read it carefully.@ Make a data table like the one shown. Then fill in the

table using information on the label.

Analysis1. What is a side effect? What side effects are caused by

this drug?2. Why should a person never take more than the

recommended dosage?3. How are over-the-counter drugs different from

prescription drugs?

MiniLab 36-2MiniLab 36-2 Analyzing Informationhave powerful effects on the nervoussystem and other systems of the body,as described in Figure 36.16.

Addiction to drugsWhen a person believes he or she

needs a drug in order to feel good orfunction normally, that person is psy-chologically dependent on the drug.When a person’s body develops achemical need for the drug in order tofunction normally, the person is physi-ologically dependent. Psychologicaland physiological dependence areboth forms of addiction.

Tolerance and withdrawalWhen a drug user experiences tol-

erance or withdrawal to a frequentlyused drug, that person is addicted tothe drug. Tolerance occurs when aperson needs larger or more frequentdoses of a drug to achieve the sameeffect. The dosage increases are nec-essary because the body becomes lessresponsive to the drug. Withdrawaloccurs when the person stops takingthe drug and actually becomes ill.


Figure 36.16The use of anabolic steroids withoutcareful guidance from a physician is illegal. Some dangerous side effects of steroid abuse include cardiovasculardisease, kidney damage, and cancer.

People with these condi-tions should avoid this drug

Correctdosage

Symptomsthis drug

willrelieve

This drugshould notbe taken

with thesemedicines

Possibleside

effects

Information from a drug label

991

Purpose Students study information foundon the labels of over-the-counterdrugs.

Process Skillsobserve and infer, analyze

Teaching Strategies■ Have students look at thepackage labels of other over-the-counter drugs.

Expected ResultsStudent tables should show thefollowing information: amongothers, children under 12 years,people with high blood pressure,heart disease, diabetes, thyroiddisease, asthma, or emphysemashould avoid this drug; drowsi-ness is a possible side effect;should not be taken with antihy-pertensive or antidepressantdrugs; will relieve nasal conges-tion associated with the commoncold, hay fever, or sinusitis; thecorrect dosage is one tablet every12 hours.

Analysis1. A side effect is any effect of

the drug other than the one itis designed to produce. Sideeffects of this drug includedrowsiness.

2. The recommended dosage isthe one that has been testedand proven to be safe. Over-the-counter medicines arepotentially harmful if notused as directed.

3. Over-the-counter drugs areavailable without a doctor’sprescription. They are not asstrong as prescription medi-cines.

Performance Ask studentsto repeat the MiniLab for otherdrug labels and include the tablesin their portfolios. Use thePerformance Task AssessmentList for Carrying Out a Strategyand Collecting Data in PASC,p. 25.

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MiniLab 36-2MiniLab 36-2CAREERS IN BIOLOGY

Pharmacist

Would you like to help peopleget well, but can’t stand the

sight of blood? Then consider acareer as a pharmacist.

Skills for the JobPharmacists read prescriptions

written by doctors and other healthprofessionals and carefully prepare containers with the correct medicine. (Few pharmacists still mix the medicine them-selves; that is done by the drug manufacturer.) Pharmacistsmust know how drugs interact and guide people in avoidingharmful combinations. They also help customers select over-the-counter medicines. Besides drugstores, pharmacists workin hospitals and nursing homes, and for drug companies andgovernment agencies. To become a pharmacist, you mustcomplete a five-year bachelor’s degree in pharmacy. You mustalso pass a state examination.

For more careers in related fields, be sureto check the Glencoe Science Web Site.

www.glencoe.com/sec/science

Treating circulatory problemsMany drugs have been developed to

treat heart and circulatory problemssuch as high blood pressure. Thesemedicines are called cardiovasculardrugs. In addition to treating highblood pressure, cardiovascular drugsmay be used to normalize an irregularheartbeat, increase the heart’s pump-ing capacity, or enlarge small bloodvessels. Discover how various types ofdrugs can affect heart rate by doingthe BioLab at the end of this chapter.

Treating nervous disordersSeveral kinds of medicines are used

to help relieve symptoms of nervoussystem problems. Among these medi-cines are stimulants and depressants.

Drugs that increase the activity ofthe central and sympathetic nervoussystems are called stimulants.Amphetamines (am FET uh meenz)

are synthetic stimulants that increasethe output of CNS neurotransmit-ters. Amphetamines are seldom pre-scribed because they can lead todependence, which you’ll read moreabout later in this chapter. However,because they increase wakefulnessand alertness, amphetamines aresometimes used to treat patients withsleep disorders.

Drugs that lower, or depress, theactivity of the nervous system arecalled depressants, or sedatives. Theprimary medicinal uses of depres-sants are to encourage calmness andproduce sleep. For some people, thesymptoms of anxiety are so extremethat they interfere with the person’sability to function effectively. Byslowing down the activities of theCNS, a depressant can temporarilyrelieve some of this anxiety.

The Misuse and Abuse of Drugs

The misuse or abuse of drugs cancause serious health problems—evendeath. Drug misuse occurs when amedicine is taken for an unintendeduse. For example, giving your pre-scription medicine to someone else,not following the prescribed dosageby taking too much or too little, andmixing medicines, are all instances ofdrug misuse. You must pay carefulattention to the specific instructionsgiven on the label of a drug you aretaking. The MiniLab on the next pageshows you how to analyze such a label.

Drug abuse is the inappropriateself-administration of a drug for non-medical purposes. Drug abuse mayinvolve use of an illegal drug, such ascocaine; use of an illegally obtainedmedicine, such as someone else’s pre-scribed drugs; or excessive use of alegal drug, such as alcohol or nico-tine. Drugs abused in this way can


OriginWORDWORD

cardiovascularFrom the Greekwords kardia, mean-ing “the heart,” andvasculum, meaning“small vessel.” Car-diovascular drugstreat problems asso-ciated with bloodvessels of the heart.

990

Career PathCourses in high school:chemistry, biology, and

other advanced science andmathematics coursesCollege: for most states, a five-year bachelor’s degree in phar-macy plus an internship; for somestates, a six-year doctoral pro-gram

Career IssueAsk students whether pharmacistsshould ever contradict informa-tion that doctors have given theirpatients. Remind the class thatthe training pharmacists receiveabout the function of the humanbody is not as thorough as thetraining doctors receive.

For More InformationFor more information aboutbecoming a pharmacist, studentscan contact the AmericanPharmaceutical Association at thefollowing address:

American PharmaceuticalAssociation

2215 Constitution Avenue, NWWashington, DC 20037

CAREERS IN BIOLOGY


Bring various nonprescriptiondrugs (such as aspirin, coughsyrup, antacids, and so on) tohold up for the class. Comparesuch things as price, type ofdrug, type of packaging, andpurpose of the drug.

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Animal Testing of MedicinesLinguistic Animals are used to testcertain drugs. Some people believe

that using animals is unnecessary. Askstudents to do some research and thenwrite an editorial for the student or localnewspaper. Have them include a copy intheir journals.

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Cultural DiversitySolomon Carter FullerStudents may obtain a more thorough under-standing of brain function by learning aboutcommon neuropathologies, such as Alzheimer’sdisease. During your discussions, emphasize the work of African American psychiatrist andresearcher, Solomon Carter Fuller (1872–1953).

Fuller taught pathology, neurology, andpsychiatry at Boston University for nearly 40

years. He was best known for expanding ourmedical knowledge in the fields of neu-ropathology and psychiatry. His research ondegenerative diseases of the brain—includingAlzheimer’s disease—was considered pioneer-ing work. In 1913, Fuller became the editor of the Westborough State Hospital Papers, an influential publication specializing in mental diseases.


BioLab and MiniLab Work-sheets, p. 160 L2

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VIDEODISC The Infinite Voyage Prisoners of the Brain: Understand-

ing Addiction (Ch. 8), 4 min.!7s~D"

Dopamine and the Craving of Narcotics (Ch. 9), 5 min.!7~$G"


cocoa, and tea—is a CNS stimulant.Its effects include increased alertnessand some mood elevation. Caffeinealso causes an increase in heart rateand urine production, which can leadto dehydration.

Nicotine, a substance found intobacco, also is a stimulant. Byincreasing the release of the hormoneepinephrine (adrenaline), nicotineincreases heart rate, blood pressure,breathing rate, and stomach acidsecretion. Although nicotine is theaddictive substance in tobacco, it isonly one of about 3000 known chem-icals found in cigarettes, many ofwhich are also harmful. Smoking cig-arettes is legal for adults. But ourever-increasing knowledge of theeffects of smoke not only on the bod-ies of smokers but on nonsmokers aswell has made cigarette smoking anincreasingly unaccepted social habit.

Depressants: Alcohol and barbiturates

As you already know, depressantsslow down the activities of the CNS.All CNS depressants relieve anxiety,but most also produce noticeablesedation.

One of the most widely abuseddrugs in the world today is alcohol.Easily produced from various grainsand fruits, such as those shown inFigure 36.19, this depressant is dis-tributed throughout a person’s bodyvia the bloodstream.

Unlike other drugs that act on spe-cific receptors, alcohol probably actson the brain by dissolving through themembranes of neurons. Once insidea neuron, alcohol disrupts importantcellular functions. For instance, itappears to block the movement ofsodium and calcium ions, which areimportant in the transmission ofimpulses and the release of neuro-transmitters.

Tolerance to the effects of alcoholdevelops as a result of heavy con-sumption. Addiction to alcohol—alcoholism—can cause the destruc-tion of nerve cells and brain damage.A number of organ diseases aredirectly attributable to chronic alco-hol use. For example, cirrhosis, ahardening of the tissues of the liver,is a common affliction of alcoholics.Figure 36.20 shows another tragicoutcome of alcoholism.


Figure 36.19Most spirits are made from fer-mented grains such as wheat, bar-ley, and rye. Wine is made fromgrapes, and cider from apples.

Figure 36.20Alcohol depresses thenervous system,impairing sensoryperception and delay-ing reaction time.

993

BioethicsPart of the procedure in getting adrug approved by the Food andDrug Administration (FDA)involves human drug tests. Thedeaths of five out of 15 partici-pants in National Institute ofHealth (NIH) drug trial in thesummer of 1993 has raised ques-tions as to the safety of thesetests. Even though participantssign a consent form, desperatelyill patients may be willing toplace themselves in inordinatelydangerous situations in hopes ofhelping to find a cure. As a result,researchers question whetherthese patients can be truly“informed” about the risksinvolved.

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Classes of CommonlyAbused Drugs

Each class of drug produces its ownspecial effect on the body, and its ownparticular symptoms of withdrawal.

Stimulants: Cocaine, ampheta-mines, caffeine, and nicotine

You already know that stimulantsincrease the activity of the centralnervous system and the sympatheticnervous system. Increased CNS stim-ulation can result in mild elevation ofalertness, increased nervousness, anx-iety, or even convulsions.

Cocaine stimulates the CNS byworking on the part of the inner

brain that governs emotions andbasic drives, such as hunger

and thirst. When theseneeds are met under

normal circumstances, neurotrans-mitters—such as dopamine—arereleased to reward centers and theperson experiences pleasure. Cocaineartificially increases levels of theseneurotransmitters in the brain. As aresult, false messages are sent toreward centers indicating that a basicdrive has been satisfied. The userquickly feels a euphoric high called arush. This sense of intense pleasureand satisfaction cannot be main-tained, however, and soon the effectsof the drug change. Physical hyperac-tivity follows, and the user is unableto sit still. Often, anxiety and depres-sion set in.

Cocaine also disrupts the body’scirculatory system by interfering withthe sympathetic nervous system.Although initially causing a slowingof the heart rate, it soon produces agreat increase in heart rate and a nar-rowing of blood vessels, known asvasoconstriction. The result is highblood pressure. Heavy use of thisdrug compromises the immune sys-tem and often leads to heart abnor-malities. Cocaine affects more thanjust the people who use it. As Figure 36.17 shows, babies of ad-dicted mothers are sometimes bornalready dependent on this drug.

As you’ve already learned, amphet-amines are stimulants that increaselevels of CNS neurotransmitters.Like cocaine, amphetamines alsocause vasoconstriction, a racingheart, and increased blood pressure.Other adverse side effects of amphet-amine abuse include irregular heart-beat, chest pain, paranoia, hallucina-tions, and convulsions.

Not all stimulants are illegal. Asshown in Figure 36.18, one stimu-lant in particular is as close as the nearest coffee maker or candymachine. Caffeine—a substancefound in coffee, cola-flavored drinks,

Figure 36.17Babies born addictedto crack cocaine areusually low in birthweight, continuallyirritable, and mayshake constantly.

Figure 36.18Caffeine can trigger acondition calledtachycardia, whenthe heart beats morethan 100 times perminute.


992

Skill Have students make atable of commonly abused drugs,summarizing their effects on thebody and the symptoms associ-ated with their withdrawal.

EnrichmentResearchers speculate that ani-mals have learned to medicatethemselves by feeding on certainplants. Zoopharmacognosy is thestudy of the use of medicinalplants by wild animals. Thisgrowing area of research involvesobserving wild animals (includingchimpanzees and bears) as theyeat plants known to have medici-nal properties and noting theresults.

In 1989, a primatologist fromKyoto University observed alethargic chimpanzee that haddiarrhea and discolored urinechewing on the bark and leaves ofa plant called Vernonia amygda-lina. The primatologist knew thatthe plant contained antibiotic andantiparasitic compounds. Theday after eating the plant, thechimp had recovered fully.

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Cocaine AbuseLinguistic Have students researchthe history of a person who has

suffered as a result of cocaine abuse.Each student should write a short essaythat includes his or her personal feel-ings about how this drug affected theperson.

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PortfolioPortfolio

Alcohol in the BodyLinguistic Ask students to write askit about the travel route of alcohol

in the body—from the mouth, into thebloodstream, and to the brain and liver.Have them place the written lines anddirections for the skits in their portfolios.

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The BioLab at theend of the chaptercan be used at thispoint in the lesson.

YOUR OWNDESIGN

YOUR OWNDESIGN

Breaking the HabitOnce a person has become

addicted to a drug, breaking the habit can be very difficult. Recall thatan addiction can involve both physio-logical and psychological depen-dencies. Besides the desire to breakthe addiction, studies have shownthat people usually need both med-ical and psychological therapy—suchas counseling—to be successful intheir treatment. Support groups suchas Alcoholics Anonymous allowaddicts to share their experiences inan effort to maintain sobriety. Often,people going through the samerecovery are able to offer the bestsupport.

Nicotine replacement therapyNicotine replacement therapy is

one example of a relatively success-ful drug treatment approach. Peoplewho are trying to break their addic-tion to tobacco often go throughstressful withdrawals when they stopsmoking cigarettes. To ease theintensity of the withdrawal symp-toms, patients wear adhesive patchesthat slowly release small amounts of nicotine into their blood-stream, as shown in Figure 36.22.Alternatively, pieces of nicotine-containing gum are chewed periodi-cally to temporarily relieve cravings.

Nicotine inhalers—similar toasthma inhalers—provide immediaterelief. By gradually decreasing theamount of nicotine released by thepatches—or the number of gumpieces chewed—cigarette smokersare able to minimize the withdrawalsymptoms that often result in a fail-ure to quit.


Understanding Main Ideas1. In what ways can drugs be used to treat a

cardiovascular problem?2. What is the difference between aspirin and a

narcotic?3. How does nicotine affect the body?4. How can drugs affect levels of neurotransmitters

between neurons?

Thinking Critically5. Suggest why a physician but not a pharmacist is

legally permitted to write prescriptions.

6. Comparing and Contrasting Distinguishbetween stimulants and depressants, comparingtheir effects on the body. For more help, refer toThinking Critically in the Skill Handbook.



Figure 36.22To help break an addiction to tobacco, this patientis wearing a patch on his arm that releases smallamounts of nicotine directly into his bloodstream.

Knowledge Have one stu-dent name a drug from the chap-ter and a second studentcategorize the drug as a stimulant,depressant, narcotic, or hallucino-gen. Have a third student list aside effect of the drug. Continuearound the class until each stu-dent has been involved.

4 CloseDiscussionAsk students to discuss the conse-quences of introducing any typeof drug into the body. Bring outthat all drugs affect body func-tion. Some drugs help the bodyestablish and maintain homeostasiswhile other drugs, those most fre-quently abused, alter homeostasis.

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AssessmentAssessmentBarbiturates (bar BIHCH uh ruts)are sedatives and anti-anxiety drugs.When barbiturates are used in excess,the user’s respiratory and circulatorysystems become depressed. Chronicuse results in both tolerance andaddiction.

Narcotics: OpiatesMost narcotics are opiates, that is,

they are derived from the opiumpoppy. They act directly on the brain.The most abused narcotic in theUnited States is heroin. It depressesthe CNS, slows breathing, and low-ers heart rate. Tolerance developsquickly, and withdrawal from heroinis painful.

Hallucinogens: Natural and synthetic

Natural hallucinogens have beenknown and used for thousands ofyears, but the abuse of hallucinogenicdrugs did not become widespread in

the United States until the 1960s,when new synthetic versions becamewidely available.

Hallucinogens (huh LEWS un uhjunz) stimulate the CNS—alteringmoods, thoughts, and sensory per-ceptions. Quite simply, the user sees,hears, feels, tastes, or smells thingsthat are not actually there. This dis-orientation can impair the user’sjudgement and place him or her insome potentially dangerous situa-tions. Hallucinogens also increaseheart rate, blood pressure, respira-tory rate, and body temperature, andsometimes cause sweating, salivation,nausea, and vomiting. After largeenough doses, convulsions of thebody may even occur.

Unlike the hallucinogens shown inFigure 36.21, LSD—or acid—is asynthetic drug. The mechanism bywhich LSD produces hallucinationsis still debated, but it may involve theblocking of a CNS neurotransmitter.


Figure 36.21Some hallucinogensare found in nature.

Mushrooms of the genus Psilocybe containthe CNS hallucinogen psilocybin. Thesemushrooms are considered sacred by cer-tain Native American tribes, who use themin traditional religious rites.

AA

Ergot, a mold disease of cerealgrains, contains ahallucinogen chemi-cally related to LSD.

BB

994

EnrichmentIntrapersonal Have inter-ested students research how

the following toxins affect thenervous system and what they areused for: saxitoxin (from redtide), physostigmine, alpha-bun-garotoxin, tetrodotoxin, anddiisopropyl fluorophosphate.

Concept DevelopmentIntrapersonal Have studentsfind out how computers are

allowing pharmacologists todesign new drugs.

3 AssessCheck for Understanding

Linguistic Have studentsmake a list of stimulants and

depressants and write a paragraphabout how these substances affectthe body.

ReteachLinguistic Have studentswrite a paragraph explaining

how nicotine replacement ther-apy helps smokers to stop smok-ing.

ExtensionHave students research informa-tion about genetic susceptibilityto alcoholism. L2

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Evaluating AdvertisingInterpersonal Ask studentsto cut out cigarette ads from

magazines. Post the ads on a bulletinboard so all students can view them. Ingroups, have students discuss who the adsare likely to influence (the targeted audi-ence). Ask students to select one ad anddiscuss its effectiveness.

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Section AssessmentSection AssessmentSection Assessment1. Drugs are used to normalize an irregu-

lar heartbeat, increase the heart’spumping capacity, or enlarge smallblood vessels.

2. Aspirin inhibits the production of impulses at the site of pain, whilenarcotics work on the central nervoussystem to relieve pain.

3. Nicotine will stimulate the central

nervous system, causing an increase inheart rate, blood pressure, and breath-ing rate.

4. Drugs can increase or decrease theamount of neurotransmitters foundbetween neurons.

5. A physician knows the medical history ofthe patient and can treat problems thatmight occur as side effects of the drug.

6. Stimulants increase the activity of the central and sympathetic nervoussystems. Depressants decrease theactivity of the central nervous systemand increase activity of the parasympa-thetic nervous system. Stimulants can increase alertness, nervousness,anxiety, heart rate, and breathing rate.Depressants do the opposite. 995


Reinforcement and StudyGuide, p. 162

Content Mastery, pp. 177,180

Tech Prep Applications, p. 49L2

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Changing Variables Many other over-the-counter drugs are available. You may wish totest their effect on the heart rate of Daphnia.

To find out more aboutdrug effects, visit the

Glencoe Science Web Site.www.glencoe.com/sec/science

PLAN THE EXPERIMENTPLAN THE EXPERIMENT

1. Using a dropper, place a singleDaphnia crustacean on a slide.

2. Observe the animal on lowpower and find its heart.

3. Design an experiment to mea-sure the effect on heart rate offour of the drug-containingsubstances in the PossibleMaterials list.

4. Design and construct a datatable for recording your data.

Check the Plan1. Be sure to consider what you

will use as a control.2. Plan to add two drops of a

drug-containing substancedirectly to the slide.

3. When you are finished testingone drug, you will need toflush the used Daphnia with thesolution into a beaker of agedtap water provided by yourteacher. Plan to use a newDaphnia for each substancetested.


1. Making Inferences Which drugsare stimulants? Which aredepressants?

2. Checking Your HypothesesCompare your predicted resultswith the experimental data.Explain whether or not your datasupport your hypotheses regard-ing the drugs’ effects.

3. Drawing Conclusions How dothe drugs affect the heart rate ofthis animal?

4. Analyzing the Procedure How

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

4. Make sure your teacher hasapproved your experimentalplan before you proceed further.

5. Carry out your experiment.CAUTION: Wash your handswith soap and water immedi-ately after making observations.

would you alter your experimentif you did it again?

Magnification: 30�

YOUR OWNDESIGN

YOUR OWNDESIGN

1. Stimulants are coffee, tea,cola, and tobacco. Coughmedicine may also be listed.Depressants are ethyl alcoholand cough medicine if it con-tains dextromethorphenhydrobromide.

2. Some students’ hypotheseswill be confirmed by theirdata; others’ will be rejected.

3. Stimulants speed up the ani-mal’s heart rate. Depressantsslow the heart rate.

4. Answers will vary.

Error AnalysisAdvise students they must haveonly a small amount of water oneach slide with their Daphnia. Ifthey have too much water, it willdilute the solutions tested.

Performance Have stu-dents each prepare a laboratoryreport that includes the experi-mental plan, the data table, andthe answers to Analyze andConclude, to be placed in theirjournals. Use the PerformanceTask Assessment List for LabReport in PASC, p. 47. L2

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ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

997


Have students compare theeffects of four over-the-countercough medicines on the heartrate of Daphnia. They shouldcarefully make equal dilutionsof each medicine after deter-mining the concentration of theactive drug in each (listed onthe package). Tablet coughmedications list milligrams ofmedication in each tablet. L2

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What drugs affect theheart rate of Daphnia?

Depending on their chemical composition, drugs affect different parts ofyour body. Stimulants and depressants are drugs that affect the cen-

tral nervous system and the autonomic nervous system. Stimulants increasethe activity of the sympathetic nervous system, which is responsible for thefight-or-flight response. They cause an increase in your breathing rate andin your heart rate. Depressants, on the other hand, decrease the activity ofthe sympathetic nervous system, reducing your breathing and heart rates.

YOUR OWNDESIGN

YOUR OWNDESIGN

ProblemWhat legally available drugs are

stimulants to the heart? What legaldrugs are depressants? Because thesedrugs are legally available, are theyless dangerous?

HypothesesBased on what you learned in this

chapter, which of the drugs listedunder Possible Materials do youthink are stimulants? Which aredepressants? How will they affect theheart rate in Daphnia? Make ahypothesis concerning how each ofthe drugs listed will affect heart rate.

ObjectivesIn this BioLab, you will:■ Measure the resting heart rate in

Daphnia.■ Compare the resting heart rate with

the heart rate when a drug isapplied.

Possible Materialsaged tap waterDaphnia culturedilute solutions of coffee, tea,

cola, ethyl alcohol, tobacco, and cough medicine (containingdextromethorphan)

droppermicroscopemicroscope slide

Safety PrecautionsDo not drink any of the solutions

used in this lab. Always wear gogglesin the lab. Use caution when workingwith a microscope, microscope slides,and glassware.

Skill HandbookUse the Skill Handbook if you need

additional help with this lab.

PREPARATIONPREPARATION

YOUR OWNDESIGN

YOUR OWNDESIGN

996

Time Allotment One class period

Process Skillsobserve and infer, form a hypoth-esis, communicate, predict, inter-pret data, experiment, andanalyze

Safety PrecautionsCaution students not to drink anyof the solutions tested and advisethem to wash their hands at theconclusion of the lab.

Solutions■ Ethyl alcohol—add 2 mL of

ethyl alcohol to 98 mL of dis-tilled water.

■ Nicotine—soak an unfilteredcigarette in 100 mL of warmdistilled water for one hour;then filter the solution.

■ Prepare weak solutions of cof-fee and tea.

■ Dilute cola l part water to 1part cola.

■ Cough medicine—add 2 mLof cough medicine to 98 mL ofdistilled water.

Possible Hypotheses■ Students’ hypotheses should

categorize each drug accordingto whether it will increase,decrease, or not affect heartrate. Coffee, tea, cola, tobacco,and possibly cough medicineare stimulants and will increaseheart rate. Ethyl alcohol andpossibly cough medicine (withdextromethorphen hydrobro-mide) are depressants and willdecrease heart rate.

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Teaching Strategies■ Age tap water by leaving it in a beakerovernight.■ Set up a distribution station for all thesolutions being tested.■ Daphnia that are placed in the aged tapwater after being tested with a drug can bereused again later.

Possible Procedures■ Students should measure the resting

heart rate of each Daphnia before addingseveral drops of one of the solutions andmeasuring the heart rate again.

No drug

Coffee

Cola

Tea

Ethyl alcohol

Tobacco

Cough medicine

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270

270

260

215

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heart rate varies with brand

Heart rate/minDrug

Data and ObservationsResource ManagerResource Manager

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Chapter 36 AssessmentChapter 36 Assessment

SUMMARYSUMMARY

Section 36.1

Section 36.2

Section 36.3

Vocabularyautonomic nervous

system (p. 981)axon (p. 973)central nervous system (p. 976)cerebellum (p. 977)cerebrum (p. 977)dendrite (p. 973)medulla oblongata (p. 977)neuron (p. 973)neurotransmitter (p. 976)parasympathetic nervous

system (p. 981)peripheral nervous

system (p. 977)reflex (p. 980)somatic nervous system

(p. 980)sympathetic nervous

system (p. 981)synapse (p. 976)

Main Ideas■ Taste and smell are senses that respond to

chemical stimulation.■ Sight is a sense that responds to light stim-

ulation.■ Hearing, balance, and touch are senses that

respond to mechanical stimulation.

Vocabularycochlea (p. 984)cones (p. 984)retina (p. 984)rods (p. 984)semicircular canals (p. 987)taste bud (p. 984)

Main Ideas■ Drugs act on the body’s nervous system.■ Some medicinal uses of drugs include

relieving pain and treating cardiovascularproblems and nervous disorders.

■ The misuse of drugs involves taking amedicine for an unintended use. Drugabuse involves using a drug for a nonmed-ical purpose.

■ Addictions can be broken with the aid ofcounseling and drug therapy.

Vocabularyaddiction (p. 991)depressant (p. 990)drug (p. 988)hallucinogen (p. 994)narcotic (p. 989)stimulant (p. 990)tolerance (p. 991)withdrawal (p. 991)

CHAPTER 36 ASSESSMENT 999

The NervousSystem

Main Ideas■ The neuron is the basic structural unit of

the nervous system. Impulses move along aneuron in a wave of changing charges.

■ The central nervous system consists of thebrain and spinal cord.

■ The peripheral nervous system relays mes-sages to and from the central nervous sys-tem. It consists of the somatic and auto-nomic nervous systems.

The Senses

The Effects of Drugs

999



Chapter Assessment, pp. 211-216MindJogger VideoquizzesComputer Test BankBDOL Interactive CD-ROM, Chapter 36

quiz

Main IdeasSummary statements can be used bystudents to review the major con-cepts of the chapter.

Using the VocabularyTo reinforce chapter vocabulary, usethe Content Mastery Booklet andthe activities in the Interactive Tutorfor Biology: The Dynamics of Life onthe Glencoe Science Web Site.www.glencoe.com/sec/science

All ChapterAssessment

questions and answers have beenvalidated for accuracy and suitabil-ity by The Princeton Review.


Scanning the Mind

Advancements in medical technology have led to instruments—such as X-ray and magnetic resonance imaging (MRI) machines—that can examine the human body in anoninvasive way. Recently, another technology has been added to the medical toolbox—

positron emission tomography (PET). This instrument is unique in that it allows aphysician to view internal body tissues while they carry out their normal daily functions.

TechnologyTechnologyBIOBIO

Thinking Critically What other body systems might be examined with the aid of a PET scanner?

To find out more about PET scans, visit the Glencoe

Science Web Site.www.glencoe.com/sec/science

INVESTIGATING THE TECHNOLOGYINVESTIGATING THE TECHNOLOGY

PET scanners are excellent tools for studyingthe human brain. By monitoring either the

blood flow to an area or the amount of glucosebeing metabolized there, doctors are able to pin-point active sections of the brain.

Here’s how it works: The patient is injectedwith a compound containing radioactive iso-topes. Because these isotopes emit detectableradiation, they can be tracked by the sensitivePET scanner. Computers create a picture ofbrain activity by converting the energy emittedfrom the radioisotopes into a colorful map. Theimage indicates the location of an activity, such asglucose utilization, and its relative intensity invarious regions.

Applications for the FuturePET scanners are important in brain

research, including the detection and diagnosisof brain tumors, the evaluation of damage due tostroke, and the mapping of brain functions.

PET scans can also be used to see how learn-ing takes place in the brain. The images on thispage show activity in the left and right brains oftwo different people. Each person was given a listof nouns and asked to visualize them. Theunpracticed brain (top) had no previous experi-ence with this exercise and thus was forced toengage in a high level of brain activity to performthe task. The practiced brain (bottom), by com-parison, was able to picture the words with muchless brain activity. Biologists can discover func-tions of different parts of the brain and their rolesin learning.

PET scans are also proving useful in the studyof drug and alcohol addiction. Addicts can begiven the addictive drug and then asked questions

about their physical and emotional status whilethe scanner records metabolic activity in thebrain. Researchers hope that information gainedfrom the study of drug addiction will providehelp in diagnosing and treating manic-depressivepsychosis and schizophrenia.

PET scans

998

Purpose Students learn how radioactiveisotopes are used in positronemission tomography (PET).

Background■ To make use of PET scanners,

patients are injected withshort-lived radioisotopes suchas C-11, N-13, or O-15. Asthe radioisotope circulatesthrough the body, it emits pos-itively charged particles calledpositrons. The positrons collidewith electrons in body tissues,causing the release of gammarays that are detected by PETreceptors.

Teaching Strategies■ Pet scanners can be used tomeasure activities that involvecirculation of chemicals or chem-ical reactions in the body. Askstudents to list some body activi-ties that doctors might be able tomonitor with PET scanners.

Investigating the TechnologyThinking Critically Any placewhere blood flows and metabolicactivities occur. Students maymention different organ systems.

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Students can find out how PETscans are used to distinguishbetween the two types ofbreast tumor: those that haveestrogen receptors and thosethat do not have estrogenreceptors.

VIDEODISCThe Infinite Voyage Fires of the Mind: Positron

Emission Tomography (PET) (Ch. 4) 3 min.

!7KVF"

VIDEOTAPEMindJogger Videoquizzes

Chapter 36: The Nervous SystemHave students work in groups as they playthe videoquiz game to review key chapterconcepts.



21. You are making a ferry crossing during roughweather and the horizon seems to be movingup and down as you hold on to the railing.You begin to feel seasick. Explain what isgoing on inside your body that might becausing this sensation.

22. Tetrodotoxin, a chemical produced by thepuffer fish, blocks sodium channels. Howdoes this toxin help the fish capture its prey?

23. Explain how alcohol disrupts the normalfunctions of a neuron.

24. Observing and Inferring A medicine has thisprecaution on its label: “Avoid driving amotor vehicle while taking this medicine as itmay cause drowsiness.” What type of drugdoes this medicine contain? Explain.

25. Concept Mapping Complete the conceptmap by using the following vocabulary terms:neurons, neurotransmitters, axons, dendrites,synapses.

THINKING CRITICALLYTHINKING CRITICALLY

APPLYING MAIN IDEASAPPLYING MAIN IDEAS


CHAPTER 36 ASSESSMENT 1001

ASSESSING KNOWLEDGE & SKILLSASSESSING KNOWLEDGE & SKILLS

As a part of his job in building a new high-way, a construction worker is planning tolight a fuse hooked to some TNT to blastout a portion of rock.

Comparing and Contrasting Use the illustration above to answer the followingquestions.1. How does the steady burning of the fuse

resemble the depolarization of a neuron?a. Both involve sodium channels.b. Both are under voluntary control.c. Both are self-propagating.d. Both involve the combustion of oxygen.

2. How do a neuron and the fuse comparein terms of repeated use?a. Neither the fuse nor the neuron can

be used repeatedly.b. The fuse can be used over and over,

but the neuron must regrow beforebeing reused.

c. The neuron can be used after recov-ery, but the fuse is consumed and cannot be reused.

d. Both the neuron and the fuse can beused repeatedly.

3. Applying Concepts In what ways is themovement of an impulse down an axonsimilar to the movement of an electriccurrent in a wire?

3.2.

contain branchlikeextensions called

contain long, singleextensions called

release chemicalscalled

4.

5.

1.

which diffuseacross

For additional review, use the assessmentoptions for this chapter found on the Biology: TheDynamics of Life Interactive CD-ROM and on theGlencoe Science Web Site.www.glencoe.com/sec/science

CD-ROM

1001

21. Your body is constantly movingup, down, and sideways. As aresult, your semicircular canalsare over-stimulated and youfeel seasick.

22. Because the prey cannot trans-port sodium across its mem-branes in order to relay animpulse to move, it is effectivelyparalyzed.

23. Alcohol blocks the movementof sodium and calcium ions,which are responsible for trans-mitting impulses.

24. The medicine may contain adepressant or mild narcotic.

25. 1. Neurons; 2. Dendrites; 3.Axons; 4. Neurotransmitters; 5.Synapses

THINKING CRITICALLYTHINKING CRITICALLY

APPLYING MAIN IDEASAPPLYING MAIN IDEAS


1. c2. c3. Both are due to the flow

of charged particles. Theelectrical current is due tothe flow of electrons,whereas the impulse isdue to the flow ofcharged ions.

Cochlea

Ovalwindow

Semicircularcanals

Stapes

1. Which of the following is NOT part of thebrain?a. cerebrum c. cerebellumb. cochlea d. pons

2. Which of the following is NOT a type ofneuron?a. interneuron c. motor neuronb. sensory neuron d. stimulus neuron

3. Which portion of the brain controls balance, posture, and coordination?

4. Which vision cells allow humans to seecolor?a. thalamic cells c. cone cellsb. rod cells d. cortex cells

5. Which part of the ear is involved in maintaining balance?

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS


6. Which drug type relieves pain by inhibitingreceptors at the site of pain?a. stimulants c. aspirinb. depressants d. narcotics

7. What type of drug is nicotine?a. stimulant c. analgesicb. depressant d. hallucinogen

8. Which of these is NOT a type of receptorfound in the dermis of the skin?a. pain c. pressureb. light d. temperature

9. Which of the following drugs depresses theactivities of the CNS?a. cocaine c. alcoholb. aspirin d. opiate

10. Which type of neuron carries impulsestoward the brain?a. sensory c. associationb. motor d. none of the above

11. The basic unit of structure and function inthe nervous system is the ________, or nervecell.

12. Most ________ are surrounded by a whitecovering called the ________ sheath.

13. When a stimulus excites a neuron, ________ions rush into the cell.

14. The ________ nervous system is made up ofthe spinal cord and the ________.

15. A(n) ________ is a single extension of a neuron that carries messages ________ thecell body.

16. A ________ is the region between one neuron’s axon and another neuron’s dendrites.

17. Chemicals called ________ diffuse acrosssynapses and stimulate neurons.

18. A(n) ________ is a psychological or physio-logical dependence on a ________.

19. The ________ on the tongue contain sensoryreceptors that send taste signals to the________.

20. Alcohol is a ________ that slows the activitiesof the ________.

1000 CHAPTER 36 ASSESSMENT

TEST–TAKING TIPTEST–TAKING TIP

Don’t Be Afraid to Ask for Help Ask for advice on things you don’t understand. Ifyou’re practicing for a test and you find yourselfstuck, unable to understand why you got a ques-tion wrong, or unable to do it in the first place,ask for help.

Cerebrum

PonsMedullaoblongata

Cerebellum

1000

1. b2. d3. cerebellum4. c5. semicircular canals6. c7. a8. b9. c

10. a11. neuron12. axons, myelin13. sodium14. central, brain15. axon, away from16. synaptic space17. neurotransmitters18. addiction, drug19. taste buds, brain20. depressant, central nervous

system

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS



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