The nervous system has two main parts: The central nervous system is made up of the brain and spinal cord. The peripheral nervous system is ...SkiptomaincontentCOVID-19GetthelatestpublichealthinformationfromCDC:https://www.cdc.gov/coronavirus/GetthelatestresearchinformationfromNIH:https://www.covid19.nih.gov/(enespañol)NIHstaffguidanceoncoronavirus(NIHOnly):https://employees.nih.gov/pages/coronavirus/HomeHealthAtoZListNeuroscienceAboutPartsofthenervoussystemShareFacebookTwitterLinkedInPinterestEmailPrintWhatarethepartsofthenervoussystem?EnEspañolThenervoussystemhastwomainparts:Thecentralnervoussystemismadeupofthebrainandspinalcord.Theperipheralnervoussystemismadeupofnervesthatbranchofffromthespinalcordandextendtoallpartsofthebody.Thenervoussystemtransmitssignalsbetweenthebrainandtherestofthebody,includinginternalorgans.Inthisway,thenervoussystem’sactivitycontrolstheabilitytomove,breathe,see,think,andmore.1Thebasicunitofthenervoussystemisanervecell,or neuron.Thehumanbraincontainsabout100billionneurons.Aneuronhasacellbody,whichincludesthecellnucleus,andspecialextensionscalled axons (pronounced AK-sonz)and dendrites (pronounced DEN-drahytz).Bundlesofaxons,callednerves,arefoundthroughoutthebody.Axonsanddendritesallowneuronstocommunicate,evenacrosslongdistances.Differenttypesofneuronscontrolorperformdifferentactivities.Forinstance,motorneuronstransmitmessagesfromthebraintothemusclestogeneratemovement.Sensoryneuronsdetectlight,sound,odor,taste,pressure,andheatandsendmessagesaboutthosethingstothebrain.Otherpartsofthenervoussystemcontrolinvoluntaryprocesses.Theseincludekeepingaregularheartbeat,releasinghormoneslikeadrenaline,openingthepupilinresponsetolight,andregulatingthedigestivesystem.Whenaneuronsendsamessagetoanotherneuron,itsendsanelectricalsignaldownthelengthofitsaxon.Attheendoftheaxon,theelectricalsignalchangestoachemicalsignal.Theaxonthenreleasesthechemicalsignalwithchemicalmessengerscalled neurotransmitters (pronounced noor-oh-TRANS-mit-erz)intothesynapse (pronoun