PeripheralNervousSystemLesson15

LearningGoals

1. Beabletodistinguishbetweentheafferentandefferentsystem

2. Beabletodistinguishbetweenthesomaticandautonomicsystem

3. Beabletodistinguishbetweenthesympatheticandparasympatheticsystem

PeripheralNervousSystem(PNS)

•Regulatesmovement(skeletalmuscles)andinternalenvironmentofthebody(organs)•CarriesinformationbetweenthebodyandtheCNS

Division

PNSisdividedinto:1. Theafferentsystem• Receivesinformationfromsensoryreceptors• Transmits informationtotheCNS

2. Theefferentsystem• Carries signalsfromtheCNStoeffectors (i.e.musclesandglands)

EfferentSystem

Efferentsystemismadeupaxonsthatcarrysignalstoeffectors

Furthersubdividedinto:1. Thesomaticsystem• Communicateswithskeletalmuscles

2. Theautonomicsystem• Communicateswiththesmoothmusclesandglands

Somaticsystem

ControlsbodymovementsandcarriessignalsfromtheCNStotheskeletalmuscles

31pairsofspinalnerves:•8cervical•12thoracic•5lumbar•5sacral

•1coccygeal

Somaticsystem

Eachservesdifferentpartsofthebody:

• Cervical– head,neck,arms,somebackmuscles• Thoracic – chestandabdomen• Lumbar– legs• Sacral– bowel,bladder,andsexorgans• Coccygeal– rectumandanus

Spinalcord

• Ventralroots relaymotorinformationfromtheCNS

• Fromthespinalcord,dorsalroot carriessensoryinformationtotheCNS

Autonomicsystem

• Workswithendocrinesystemtoregulatethebodyinresponsetochangesintheinternalandexternalenvironment

• Alwaysactive!à Largelyinvoluntaryprocesses• 2brancheshaveopposingfeatures:

1. Sympathetic– “fightorflight”• Moreactiveduringstressfulsituations

2. Parasympathetic– “restanddigest”• Moreactiveduringquiet,lowstresssituations

Autonomicsystem• Eachpathwayinthissystemusestwoneurons• DendritesandcellbodyofthefirstneuronareintheCNSanditsaxonextendstoaganglionoutsidetheCNS• Aganglion=enlargementofthenervewherethecellbodiesoftheneuronsarelocated• Axonofthesecondneuronextendsfromthegangliontotheeffector(response)

Autonomicsystem

Organizedintosympatheticandparasympatheticvisions:

1. Sympathetic– stressfulsituationsthatinvolvestressorexcitement• Increaseheartbeatrate,raisebloodpressure,dilateairpassageinlungs,inducesweatingandopenpupils

2. Parasympathetic – quiet,lowstresssituations

Autonomicsystem

Organ Sympathetic Parasympatheticheart Increaseheartrate Decreaseheartrate

digestive Decreaseperistalsis Increasesperistalsisliver Increases thereleaseof

glucoseStoresglucose

eyes Dilatespupils Constrictspupilsbladder Relaxessphincter Contractssphincterskin Increasesbloodflow Decreases bloodflow

adrenalgland Causesreleaseofepinephrine

no effect

Homework

• Textbook:pg.434Q.1,3,6;pg.437Q.1,2

• Handoutquestions

• NoFridayorMondayquiz

•UnitTest:NextWednesday(8th)

• Tomorrow:workperiodinthecomputerlab(unittask)