Nervous tissue

Introduction to nervous tissue
Cells of nervous tissues
Neuron
Neuroglia
Classification of neuron
Function of nervous tissue

1. Chapter: 2
The Tissues
Part 2: Nervous tissue
By: BithikaBaidya
Content:
1. Introduction to nervous tissue
2. Cells of nervous tissue
-Neuron
-Neuroglia cell and types of neuroglia cells
3. Classification of neurons
4. Function of nervous tissue

2. ❖Introduction to nervous tissue
•Nervoustissueisthetermforgroupoforganized
cellsinnervoussystem(consistofCNSandPNS).
•Nervoussystemcoordinatesallthevoluntaryand
involuntaryactionofbodybysendingandcarrying
signalstoandfromthedifferentpartsofthebody.
•Thesignalsentbythenervoussystemareelectrical
signalcallednerveimpulseandtheyaretransmitted
byspecializednervoussystemcellscalledtheneuron
ornervecells.
https://www.google.com/search?q=neuron+animation&source=lnms&tbm=isch&
sa=X&ved=2ahUKEwjxqTQ2LXrAhWzwzgGHQOMDEoQ_AUoAnoECA4QBA&biw=139
6&bih=686#imgrc=BqVkPTYUPPRpeM&imgdii=qOpqWKqkDQNkFM

3. ❑CELLS OF NERVOUS SYSTEM :
❖Nervoustissueconsistsoftwotypesofcells:
a)Neurons:
Neuronprovidemostoftheuniquefunctionsofthe
nervoussystem,suchassensing,controllingmuscle
activity,regulatingglandularsecretions,etc.
a)Neuroglia:
Neurogliasupport,nourish,andprotecttheneurons.

4. ❖Neuron
•SantiagoCajalwasaNeuroscientistandaNobel
laureateprovideddetaileddescriptionsofnervecell.
•Anervecellwithallitsprocessesiscalledaneuron.Itis
thestructuralandfunctionalunitofthenervoussystem.
•Mostneuronshavethreeparts:(1)acellbody,(2)
dendrites,and(3)anaxon.
1)CELLBODY:
•Thecellbody,alsoknownastheperikaryonorsoma,containsa
nucleussurroundedbycytoplasmthatincludescellularorganelles.
•Neuronalcellbodiescontainfreeribosomesandprominentclusters
ofRER,termedNisslbodies.
•Theribosomesarethesitesofproteinsynthesis.Newlysynthesized
proteinsproducedbyNisslbodiesareusedtoreplacecellular
componentsasmaterialforgrowthofneuronsandtoregenerate
damagedaxons.

5. 2. DENDRITES:
•Dendriteordendronistheprocessthatcarriesimpulsetowardsthecell
bodyfromsensorycells,axons,orotherneurons.
•Dendritespossessarborizedterminals,whichpermitaneurontoreceive
stimulisimultaneouslyfrommanyotherneurons.
•Itcollectsimpulsesfromotherneuronsandcarriesthemtowardsthecell
body.
•TheircytoplasmcontainsNisslbodies,mitochondria,andother
organelles.
3)AXON
•Thesingleaxonofaneuronpropagatesnerveimpulsestowardanother
neuron,lengthofaxonsvary.
•Axonsoriginatefromapyramid-shapedregionoftheperikaryoncalled
theaxonhillock.
•Theplasmamembraneoftheaxonisoftencalledtheaxolemmaandits
contentsareknownasaxoplasm.
•Alongthelengthofanaxon,sidebranchescalledaxoncollateralsmay
branchoff,typicallyatarightangletotheaxon.
•Theaxonanditscollateralsendbydividingintomanyfineprocesses
calledaxonterminals(telodendria)
•Thesiteofcommunicationbetweentwoneuronsorbetweenaneuronand
aneffectorcelliscalledasynapse.Thetipsofsomeaxonterminalsswell
intobulb-shapedstructurescalledsynapticendbulbs.

6. ❖Neuroglia:
•Neuroglialcellsarespecialtypeofinterstitialcellsthatoutnumber
neuronsbyapproximately10to1.
•Thesecellsareembeddedinaweboftissuecomposedofmodified
ectodermalelements;theentiresupportingstructureistermedthe
neuroglia.
•Theyfunctiontosupportandprotectneurons,buttheydonot
conductimpulses
•Therearesixtypesofglialcells
a)Oligodendrocytes
b)Astrocytes-ii)Protoplasmicastrocytesiii)Fibrousastrocytes
c)Ependymalcells
d)Microglia
e)Schwanncells
f)Satellitecells

7. a) Oligodendrocytes
Oligodendrocytes(Gr.oligos,small,few+dendron,tree+kytos,
cell)producethemyelinsheaths,themyelinsheathisa
multilayeredlipidandproteincoveringaroundsomeaxonsthat
insulatesthemandincreasesthespeedofnerveimpulseconduction.
Suchaxonsaresaidtobemyelinated.
b)Astrocytes:
▪Astrocytes(Gr.astron,star+kytos)havealargenumberof
radiatingprocesses.Astrocytesarebyfarthemostnumerous
glialcellsoftheCNS,aswellasthemostdiversestructurally
andfunctionally.
▪Thosewithrelativelyfew,longprocessesarecalledfibrous
astrocytesandaretypicalinwhitematter;thosewithmany
shorter,branchedprocessesarecalledprotoplasmicastrocytes
andpredominateinthegraymatter.

8. c)Ependymalcells:
➢Ependymalcellsarecuboidaltocolumnarcellsarranged
inasinglelayerthatpossessmicrovilliandcilia.
➢Thesecellslinetheventriclesofthebrainandcentral
canalofthespinalcord(spacesfilledwithcerebrospinal
fluid,whichprotectsandnourishesthebrainandspinal
cord).
➢Functionally,ependymalcellsproduce,possiblymonitor,
andassistinthecirculationofcerebrospinalfluid.
d)Microglia
➢MICROGLIATheseneurogliaaresmallcellswithslender
processesthatgiveoffnumerousspinelikeprojections.
Microgliafunctionasphagocytes.
➢Theyremovecellulardebrisformedduringnormal
developmentofthenervoussystem.
➢Theyareantigen-presentingcellsoftheCNS.

9. e)SchwannCells
➢ThesecellsencirclePNSaxons.
➢Likeoligodendrocytes,theyformthemyelinsheatharound
axons.
➢However,asingleoligodendrocytemyelinatesseveral
axons,buteachSchwanncellmyelinatesasingleaxon.
➢Schwanncellsparticipateinaxonregeneration,whichis
moreeasilyaccomplishedinthePNSthanintheCNS
f)Satellitecells
➢TheseflatcellssurroundthecellbodiesofneuronsofPNS
ganglia.
➢Besidesprovidingstructuralsupport,satellitecellsregulate
theexchangesofmaterialsbetweenneuronalcellbodiesand
interstitialfluid

10. ➢Origin, location and principal functions of neuroglialcells.

11. •ClassificationofNeurons
Structurally,neuronsareclassifiedaccordingtothe
numberofprocessesextendingfromthecellbody
1.Multipolarneuronsusuallyhaveseveraldendrites
andoneaxon.Mostneuronsinthebrainandspinal
cordareofthistype.
2.Bipolarneuronshaveonemaindendriteandone
axon.Theyarefoundintheretinaoftheeye,inthe
innerear,andintheolfactoryareaofthebrain.
3.Unipolarneuronshavedendritesandoneaxon
thatarefusedtogethertoformacontinuousprocess
thatemergesfromthecellbody.Theseneuronsare
alsoknownaspseudounipolarneuronsbecause
theybeginintheembryoasbipolarneurons.
Duringdevelopment,thedendritesandaxonfuse
togetherandbecomeasingleprocess.
4.Anaxonicneuron:Itisatypeofneuronwherethe
differentiationofaxonfromthedendritescannotbe
done.Suchanaxonicneuronsarepresentinbrain
andretina.

12. Function Of Nervous Tissue
•Neuronsgenerateandcarryoutnerveimpulses.
•Theyproduceelectricalsignalsthataretransmittedacross
distances,theydosobysecretingchemical
neurotransmitters.
•Respondstostimuli
•Carriesoutcommunicationandintegration
•Provideselectricalinsulationstonervecellsandremoves
debris
•Carriesmessagesfromotherneuronstothecellbody
•Diagram of Neuron

13. Question:
1.Draw a well-labeled diagram of Neuron. Describe its structural component.
2.Write a note on neuroglia cells.
3.Classification of neurons
4.Define: Axon, Nisslbodies, Myelin sheath, Axolemma, Axoplasm, Node of Ranvier, Axon Hillock, Saltatoryconduction,
Neuroglia cells,anaxonicneurons
References:
•PrinciplesofAnatomyandPhysiology12
th
EditionbyGerardJ.TortoraandBryanDerricksonValencia
•CCChatterjee'sHumanPhysiology12
th
edition
•Cellbiologyandhistology/LeslieP.Gartner,JamesL.Hiatt,JudyM.Strum.—6thed
•Junqueira’sBasicHistologyTextandatlas13
th
Edition,AnthonyL.Mescher
Thank You….