Section3: TheImmuneSystem

Unit1:CellsandSystems

I.TheImmuneSystemandTransmissionofInfectiousDiseases

• Theimmunesystemattacksanddestroysinvadersthatenterthebody.

• Pathogens areorganismsorsubstancesthatcausedisease(germs)

• Antigensareanynon-living substancethatisforeigntothebodyandtriggersanimmuneresponse(i.e.,splinter,plantpollen,viruses)

Diseasescanbespreadby:

• Direct contact(shakinghands,sharingbodyfluids)

• Indirect contact(sneezing,coughing)

• Water andFood (eatingfoodsordrinkingwaterinfectedwithpathogens)

• Animalbites

II.FightingInfections

a)1st LineofDefense– BodypreventspathogensfrominfectinghostSkinandliningsofallinternalorgans• Sweat andoil(slightlyacidic,preventingsomepathogensfromgrowing)

• Gastric juicesecretedbytheliningofthestomach

• Mucus andCilia (linethenosepreventingpathogensfromenteringrespiratorysystem)

Describewhateachofthefollowing“entrypoints”dotoprevententryofpathogensintothebody:

“Entrypoint” Entryblockedby…

Eyes Tears,eyelashes

Ears Earwax

Nose Mucus,cilia

Mouth(andstomach)

Gastricjuice

b)2nd LineofDefense- Bodymountsanimmuneresponsetoanattack

TwoTypes:

• InnateImmuneResponse

•AcquiredImmuneResponse

I)Innate ImmuneResponse- general,non-specific(sameforanyinvader)

• fluid,cellsanddissolvedsubstancesinthebloodflow tothesiteofinfection

• thisresultsinfever,swelling,andredness(inflammation)

• white bloodcellsinthebloodengulfintruders,destroyingthem– calledPHAGOCYTOSIS

https://www.youtube.com/watch?v=X-ubCIcAh4M

II)Acquired ImmuneResponse- morespecific attackonaparticularpathogen

• Consistsof4stages:1. Recognition

2. Mobilization

3. Disposal

4. Immunity

1.Recognition

• whenbodyisinvadedbyaforeignsubstance,thebodyrecognizesitasnotbelonging

• Thebodyuseswhite bloodcellstorecognizeinfectionandtofighttheinvadingdisease-causingagent,orpathogen.

• Phagocytesengulf (eat)theinvadingbacteriaandsignalHelperTcellstofindBcellsandtellthemtoproduceantibodies.

2.Mobilization• Bcellsmakeantibodies,whichbindtoantigenstomakethemharmlessormarkthemfordestructionbyotherwhitebloodcells

–Musthaveaperfectfit=lockandkey

– Thiscantaketime– thisiswhyyoucanbesickfordays/weeks.

3.Disposal

• Oncetherightantibodythatfits theantigenisfound,theyaremassproducedandclumpontotheinvadingpathogen,markingitfordestruction.

• KillerTcells killthebody’sowncells thathavebeeninvadedbypathogens,preventingthepathogenfromreproducing inthecellandtheninfectingothercells.

4.Immunity

• Someantibodiesremainforfuture use– youusuallycannothavethesamediseasetwice!

3.2FactorsAffectingtheImmuneSystem

I.Vaccinations• Vaccinesareweakenedpathogens giventopeopletoprotectthemfromgettingadisease.

• Vaccinesstimulateyourbodytocreateantibodies todestroythepathogen.

• Theseantibodieswillactivate whenthepathogenentersthebodyagain.

• Booster shotsincreasetheantibodyproductionandextendtheimmunesystem’smemoryforthatantigen.

II.DisordersoftheImmuneSystemALLERGIES:• Anallergyisanunusuallyhighsensitivitytoasubstance.

• Anysubstancethatcausesanallergicreactioniscalledanallergen.

• Sideeffectsofanallergicreactionarearesultofhistamine.Histamineisachemicalthatyourbodyreleaseswhenyouneedtofightinvaders.

• Severeallergiescancauseanaphylactic shock(swelling,breathingdifficulties,andsometimesdeath).

III.AIDS/HIV• AcquiredImmunodeficiencySyndrome(AIDS)isaninfectionoftheimmunesystemthatleadstohealthcomplicationsandoftendeath.

• AIDSiscausebythehumanimmunodeficiencyvirus(HIV)thatattackstheimmunesystembyinfectingHelper T-cells.

• AIDSistransmittedbyblood andsemen.

• There’snocureforHIV/AIDS,butavarietyofmedications canbeusedincombinationtocontrolthevirus.

IV.TakingCareofyourImmuneSystem• Eatawell-balanced diet• Maintainpersonalhygiene (bathing,washinghands,brushingteeth)

• Keephomeclean• Avoidtobaccoandothernon-prescriptiondrugs• Getplentyofrestandexercise• Keepvaccinations uptodate• Donotengageinactivitiesthatinvolvesharingbodyfluids withothers.

3.3EpidemicsandPandemics

• Adiseaseissaidtobeendemic whenitisataconstant,“normal”occurrencewithinagivengeographicalarea.Inthiscase,low numbersofpeoplebecomesick.

• Adiseasebecomesan epidemic whenitaffectsanunusualnumberofpeopleinacommunityorregionatthesametime.Ahigher numberofpeoplebecomesick.

Characteristicsoranepidemic:

–Whenthe#ofpeopleinfectedrises abovewhatisexpected.– Illnessisspecifictoacertainarea.–Usuallycausedbycirculation amongpeople.

ExamplesofEpidemics:

• seasonalflu outbreakshappeneachyear• Norovirus outbreakshaveoccurredoncruiseships

• in2003,thesevereacuterespiratorysyndrome(SARS)epidemictookthelivesofnearly800peopleworldwide

• in2014,theEbolavirus resultedin6070deathsinWestAfrica

Pandemics

• Adiseaseisapandemic whenitbecomesprevalentthroughoutanentirecountry,continent,orthewholeworld.

• Thousandstomillionsofpeoplebecomesick.

Characteristicsofapandemic:

• Causesseriousillness.• illnessspreads easilyfromperson.• isanoutbreakofglobal proportions.• usuallycausedbyanewformofavirusorbacteria.

ExamplesofPandemics:

• Spanishflu killed40-50millionpeoplein1918

• TheFranco-PrussianWartriggereda smallpoxpandemic of1870–1875thatclaimed500,000lives

• HIV/AIDS

• In2009,H1N1

Howmanypeoplediefromapandemicdependsupon:

• Thenumberofpeoplewhobecomeinfected• Theseverityofdiseasecausedbythevirus(itsvirulence)

• Thevulnerability ofaffectedpopulations• Theeffectiveness ofpreventivesteps

TheWorldHealthOrganization (WHO)providesaninfluenzapandemicalertsystem,withascalerangingfromPhase1(alowriskofaflu pandemic)toPhase6(afull-blownpandemic):

• Phase1: Avirusinanimalshascausednoknowninfectionsinhumans.

• Phase2: Ananimalfluvirushascausedinfectioninhumans.• Phase3: Sporadiccasesorsmallclustersofdiseaseoccurin

humans.Human-to-humantransmission,ifany,isinsufficienttocausecommunity-leveloutbreaks.

• Phase4: Theriskforapandemicisgreatlyincreasedbutnotcertain.

• Phase5: SpreadofdiseasebetweenhumansisoccurringinmorethanonecountryofoneWHOregion.

• Phase6: Community-leveloutbreaksareinatleastoneadditionalcountryinadifferentWHOregionfromphase5.Aglobalpandemicisunderway.

Howtopreventthespreadofdiseases?

• Thebestwaytopreventavirusfrombecomingapandemicistogetavaccination.

• Washyourhands oftenwithsoapandwater.Ifthesearenotavailable,useanalcohol-basedhandcleanerorgelsanitizer.Ifusingagel,rubyourhandsuntiltheybecomedry.

• Avoidtouching your mouth,nose,or eyes withyourhandsunlessyou'vejustwashedyourhands.

• Whenyou cough orsneeze,coveryour mouth andnose withatissue.Thenthrowthetissueinthetrash. Washyourhandsafterward.

• Avoidcrowdedplaces asmuchasyoucanandstayhomeifyoushowsignsofillness.

• Dependingontheseverityofthepandemic,considerwearingafacemask ifyoumustgointoacrowdedareaorbewithin6feetofothers.

• Considerwearingafacemaskifyoumustcomeintoclosecontactwithaninfected person.