NervousSystemLesson11

ReflexArcs1. Patellarreflex

• Causeslegtokickup

2. Achillesreflex• Causesfoottojerkforward

3. Tricepsreflex• Causesarmtostraighten

4. Babinskireflex

4. PupilDilationReflex• Causespupiltodilateinthedarkandconstrictinlight

LearningGoals

1. Howisthenervoussystemdivided?

2. Whatarethecomponentsofaneuron?

3. Howdoesaneuralcircuitwork?

4. Whatisareflexarc?

OrganizationoftheNervousSystem

NervousSystem:complexnetworkofnervesandcellsthatcarrymessagestoandfromthebrainandspinalcordtothebody

2functionalsystems:• CentralNervousSystem(CNS)• Brainandspinalcord

• PeripheralNervousSystem(PNS)• NervesthatcarryinformationbetweenorgansandCNS

PeripheralNervousSystem

1. Sensory(afferent)somaticnervesà relayinformationaboutenvironmenttoCNS

a) Somaticb) Autonomic

2. Motor(efferent)somaticnervesà initiateanappropriateresponse

PeripheralNervousSystem

1. Somaticsystemà skeletalmuscle,skin,sensoryorgans(voluntary)

2. Autonomicsystemà internalorgancontroli.e.smoothmusclesandglands(involuntary)a) Sympatheticà nervecellsthatpreparebodyforstress(“fightorflight”)b) Parasympatheticà nervecellsthatreturnthebodytoanormalstateafter

stress(“restordigest”)

Neuron(nervecell)• Specializednervecellthatisthefunctionalunit ofthenervoussystem• Allowsorganismstoreceive andrespond tobothinternalandexternalstimuli

3mainparts1. Dendrites – receiveinformationà Cellbody2. Cellbody – informationistransmittedawayfromthebodyà axon3. Axon– informationissentalongtheaxonà neuron,muscle,organ,gland

Theneuron(nervecell)Aneuron isaspecializednervecellthatisthefunctionalunitofthenervoussystem

1. Cellbody• Containsnucleusandmostcellorganelles

2. Dendrites• Highlybranchedprojectionsthatreceivesignalsandtransmitsthemtowardsthecellbody

3. Axons• Conductssignalstowardsanotherneuronoraneffector

4. Axonterminal• Enablesthesignalstothetransmittedfromoneneurontoanotheroraneffector

Theneuron(nervecell)

5. Nucleus• OrganellewhereDNAisstored

6. Schwanncells• Aglialcell;formtightlywrappedlayersofplasmamembranecalledmyelinsheath

• Glialcells:Containsnucleusandmostcellorganelles;donot conductsignals;providesupportandnutrientstoneurons

7. Myelinsheath• Fattyproteinthatactsaselectricalinsulatorsandhelpincreasespeedofimpulses

8. NodesofRanvier• GapbetweenSchwanncellswhichexposetheaxondirectlytoextracellularfluids

NeuralCircuitConsistsof5components:

1. Receptor• Detectionofstimulibysensoryreceptorsonafferent

neurons

2. Afferentneuron(sensor)• Transmission(movement)ofamessagealongafferentneuronstointerneurons3. Interneuron• InterpretationofneuralmessagesintheCNSanddeterminationoftheappropriateresponse4. Efferentneuron(motor)• Efferentneuronstransmitresponsesignalsfrominterneuronstoeffectors5. Effector• Transmissionofneuralmessagetoeffectors(i.e.skeletalmuscles,glands,organs),where

appropriateactionoccurs

ReflexArc

• Simplestnervecircuitpathway

• Allowsquickreactionusinganeuralcircuitthroughthespinalcord

• Governsanumberofcommonbodyresponses,especiallythosewhicharerepeated(e.g.,breathing,heartbeat,sweatglandsecretion,etc.)• Doesnot involvethebrain• However,interneuronsconnectedtoreflexcircuitsalsosendsignalstothebrain,makinganindividualawareofthestimulusthatcausedthereflex

Summary1. Howisthenervoussystemdivided?

• CNSandPNS

2. Whatarethecomponentsofaneuron?

• Dendriteà cellbodyà axon

3. Howdoesaneuralcircuitwork?

• Stimulià afferentneuronà interneuronà efferentneuronà response

4. Whatisareflexarc?

• Neuralpathwaythatcontrolsareflex(arapid,involuntaryresponsetoastimulus)

Homework

•Worksheetquestions