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The Nervous System Name:_________________________________________Class:__________Date:____________
Vocabulary
Term Definition endocrine system Systemofglandsthatsecretehormonesintothebloodstream.nerve Bundleofnervecells.nervous system Bodysystemthatsendselectricalmessagesthroughoutthebody;controlsallother
bodysystems.organ system Groupsoforgansthatworktogethertoperformaspecifictask.
What body system helps you learn? Asthesegirlsarestudying,manyprocessesaretakingplace.Theireyeshavetotakeinthewordsonthepage,andtheirbrainshavetoprocessthemeaningofthewords.Thebrainalsohastoassimilatetheknowledgesoitcanberetrievedatalatertime.Alltheseprocessesarecontrolledbythenervoussystem.Introduction to the Nervous System Michellewasridingherscooterwhenshehitaholeinthestreetandstartedtolosecontrol.Shethoughtshewouldfall,but,intheblinkofaneye,sheshiftedherweightandkeptherbalance.Her
heartwaspounding,butatleastshedidn’tgethurt.Howwassheabletoreactsoquickly?Michellecanthankhernervoussystemforthat.Stayingbalancedwhenridingascooterrequirescontroloverthebody’smuscles.Thenervoussystemcontrolsthemusclesandmaintainsbalance.Thenervoussystem,togetherwiththeendocrinesystem,controlsalltheotherorgansystems.Thenervoussystemsendsonetypeofsignalaroundthebody,andtheendocrinesystemsendsanothertypeofsignalaroundthebody.Theendocrinesystemmakesandreleaseschemicalmessengermolecules,orhormones,whichtellotherbodypartsthatachangeorareactionisnecessary.Sowhattypeofsignaldoesthenervoussystemsend?Controllingmusclesandmaintainingbalancearejusttwooftherolesofthenervoussystem.Thenervoussystemalsoletsyou:• Senseyoursurroundingswithyoureyesandothersenseorgans.• Sensetheenvironmentinsideofyourbody,includingtemperature.• Controlyourinternalbodysystemsandkeeptheminbalance.• Prepareyourbodytofightorfleeinanemergency.• Uselanguage,think,learn,andremember.• Thenervoussystemworksbysendingandreceivingelectricalsignals.Themainorgansofthenervous
systemarethebrainandthespinalcord.Thesignalsarecarriedbynervesinthebody,similartothewiresthatcarryelectricityalloverahouse.Thesignalstravelfromalloverthebodytothespinalcordanduptothebrain,aswellasmovingintheotherdirection.Forexample,whenMichellestartedtofalloffherscooter,hernervoussystemsensedthatshewaslosingherbalance.Itrespondedbysendingmessagesfromherbraintomusclesinherbody.Somemusclestightenedwhileothersrelaxed.Maybethese
actionsmovedherhipsorherarms.Thenervoussystem,workingtogetherwiththemuscularandskeletalsystems,allowedMichelletoreacttothesituation.Asaresult,Michelle’sbodybecamebalancedagain.Themessagesreleasedbythenervoussystemtraveledthroughnerves.Justliketheelectricitythattravelsthroughwires,nervequicklycarrytheelectricalmessagesaroundthebody.
• Thinkabouthowquicklyallthishappens.Ithastobereallyfast,otherwiseMichellewouldnothavebeenabletoreact.WhatwouldhappenifacarpulledoutunexpectedlyinfrontofMichelle?Asignalwouldhavetogofromhereyestoherbrainandthentohermuscles.Whatallowsthenervoussystemtoreactsofast.Itstartswiththespecialcellofthenervoussystem,theneuron.
Summary
• Thenervoussystemsendselectricalmessagesthroughoutthebodyandcontrolsallotherbodysystems.
• Thenervoussystemallowsyoutothink,learn,senseyoursurroundings,andcontrolyourinternalbodysystems.
Review
1. Whatarethreefunctionsofthenervoussystem?2. Whattypeofsignalsdoesthenervoussystemsend?Whatcarriesthesesignals?3. Whatarethemainorgansofthenervoussystem?
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