Chapter7-NervousSystemNERVOUSSYSTEM:OVERVIEWDonnaMerglerandJoséA.ValciukasKnowledgeofthenervoussystemingeneralandofthebrainandhumanbehaviourinparticularareofparamountimportancetothosewhoarededicatedtoasafeandhealthyenvironment.Workconditions,andexposuresthatdirectlyaffecttheoperationsofthebrain,influencethemindandbehaviour.Toevaluateinformation,tomakedecisionsandtoreactinaconsistentandreasonablemannertoperceptionsoftheworldrequirethatthenervoussystemfunctionsproperlyandthatbehaviournotbedamagedbydangerousconditions,suchasaccidents(e.g.,afallfromapoorlydesignedladder)orexposuretohazardouslevelsofneurotoxicchemicals.Damagetothenervoussystemcancausechangesinsensoryinput(lossofvision,hearing,smell,etc.),canhinderthecapacitytocontrolmovementandbodyfunctionsand/orcanaffectthebrain'scapacitytotreatorstoreinformation.Inaddition,alterednervoussystemfunctioningcancausebehaviouralorpsychologicaldisorders.Moodandpersonalitychangesareacommonoccurrencefollowingphysicalororganicdamagetothebrain.Asourknowledgedevelops,wearelearningmoreaboutthewayinwhichnervoussystemprocessesaremodified.Neurotoxicsubstancescancrossthebrain'snaturalbarrieranddirectlyinterferewithitsintricateworkings.Althoughsomesubstanceshaveaparticularaffinitytocertainareasofthenervoussystem,mostneurotoxinshavewidespreadeffects,targetingcellprocessesinvolvedinmembranetransport,internalcellularchemicalreactions,liberationofsecretorysubstances,andsoon.Damagetothevariouscomponentsofthenervoussystemcanoccurindifferentways:·directphysicalinjuryfromfallingobjects,collisions,blowsorunduepressureonnerves·changesintheinternalenvironment,suchasinsufficientoxygenduetoasphyxiantsandheatexposure·interferenceinthecellularprocessesthroughchemicalactionbysubstances,suchasmetals,organicsolventsandpesticidesTheinsidiousandmultifaceteddevelopmentofmanynervoussystemdisordersrequirespersonsworkinginthefieldofoccupationalhealthtoadoptdifferentbutcomplementaryapproachestothestudy,understanding,preventionandtreatmentoftheproblem.Earlyalterationscanbedetectedingroupsofactive,exposedworkersusingsensitivemeasuresofimpairment.Identificationofinitialdysfunctioncanleadtopreventiveactions.Inthelatterstages,agoodclinicalknowledgeisrequiredanddifferentialdiagnosisisessentialtotheadequatetreatmentandcareofdisabledworkers.Althoughchemicalsubstancesaremostlyexaminedonebyone,itshouldberememberedthatinmanyworkplacesmixturesofpotentiallyneurotoxicchemicalsareused,exposingworkerstowhatcanbecalleda"cocktail".Inprocessessuchasprinting,painting,cleaning,inpoorlyventilatedoffices,inlaboratories,pesticideapplication,microelectronicsandmanyothersectors,workersareexposedtochemicalmixtures.Althoughtheremaybeinformationoneachoneofthesubstancesseparately,wehavetoconsiderthecombinednocivityandpossibleadditiveorevensynergisticeffectsonthenervoussystem.Insomecasesofmultipleexposure,eachparticularchemicalmaybepresentinverysmallquantity,evenbelowthedetectionlevelofexposureassessmenttechniques;however,whenallareaddedtogether,thetotalconcentrationcanbeveryhigh.ThereadershouldbeawareofthreemajordifficultiesinreviewingfactsaboutthenervoussystemwithinthescopeofthisEncyclopaedia.First,theunderstandingofoccupationaldiseasesaffectingthenervoussystemandbehaviourhaschangedsubstantiallyasnewapproachestoviewingbrain-behaviouralrelationshipshavedeveloped.Themaininterestofcharacteriz...
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