Histology of the Nervous System

Nervous Tissue

Histology of the Nervous System

Nervous Tissue

TJ del Mundo, MD, DPBOTJ del Mundo, MD, DPBO

environmentenvironment

animalanimalorganismorganism

animalanimalorganismorganism

Nervous systemNervous system

sensory sensory neuronneuron

stimulusstimulus reactionreaction

effectoreffectorInter-Inter-

neuronneuronreceptorreceptorMotorMotor

neuronneuron

Nervous System Nervous System stimulus and reaction stimulus and reaction Nervous System Nervous System stimulus and reaction stimulus and reaction

Nervous SystemNervous SystemNervous SystemNervous System

• Central Nervous SystemCentral Nervous System brain, spinal cord: brain, spinal cord: nervous tissuenervous tissue meninges, choroid plexus: meninges, choroid plexus: connective tissueconnective tissue

• Peripheral Nervous SystemPeripheral Nervous System nerve, ganglion, nerve plexusnerve, ganglion, nerve plexus:: nervous tissuenervous tissue and and connective tissueconnective tissue

cf.cf. SomaticSomatic vs vs AutonomicAutonomic Nervous System Nervous System Enteric Nervous SystemEnteric Nervous System

Nervous TissueNervous TissueNervous TissueNervous Tissue

Cellular ElementsCellular Elements

- - Neuron (Nerve Cell)Neuron (Nerve Cell)

- Neuroglial Cells- Neuroglial Cells central neurgliacentral neurglia

astrocyte, oligodendrocyte, microglia andastrocyte, oligodendrocyte, microglia and ependymal cellependymal cell

peripheral neurogliaperipheral neuroglia Schwann cell Schwann cell in nerve and ganglionin nerve and ganglion satellite (capsular) cell satellite (capsular) cell in ganglionin ganglion

Intercellular SubstanceIntercellular Substance: extremly scarse: extremly scarse

NeuronNeuronNeuronNeuron

Neuronal MorphologyNeuronal Morphology

Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)

- Nucleus - Nucleus - - PerikaryonPerikaryon

Neuronal ProcessesNeuronal Processes

AxonAxon DendritesDendrites

cf. Diversity of Neuronal Size and Morphologycf. Diversity of Neuronal Size and Morphology

Diversity ofDiversity of

NeuronalNeuronal

MorphologyMorphology

1. nucleus1. nucleus

2. perikaryon 2. perikaryon

3. cell body3. cell body

4. axon4. axon

5. dendrite5. dendrite

6. Nissl body6. Nissl body

7. axon hillock7. axon hillock

8. myelin sheath8. myelin sheath

9. oligodendrocyte9. oligodendrocyte

10. Schwann cell10. Schwann cell

11. skeletal muscle cell11. skeletal muscle cell

12. neuromuscular junction12. neuromuscular junction

Morphology of

Typical Motor Neuron

Morphology of

Typical Motor Neuron

NeuronNeuronNeuronNeuron

Neuronal FunctionNeuronal Function

CommunicationCommunication

Receptor - Neuron - Effector Receptor - Neuron - Effector - - Excitability (Irritability)Excitability (Irritability) - - ConductivityConductivity through membrane through membrane in intraneuronal conductionin intraneuronal conduction

via via synapsesynapse in in interneuronal conductioninterneuronal conduction neurotransmittersneurotransmitters

Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)

NUCLEUSNUCLEUS

ŸŸ Chromatin Pattern: Chromatin Pattern: EuchromaticEuchromatic euchromatin >>> heterochromatineuchromatin >>> heterochromatin

active active mRNAmRNA transcription transcription

cf. Barr bodycf. Barr body (facultative heterochromatin)(facultative heterochromatin)

inactive inactive X chromosomeX chromosome in female in female

ŸŸ Conspicuous NucleolusConspicuous Nucleolus NOR (nucleolar organizing region)NOR (nucleolar organizing region)

activeactive rRNArRNA transcription -- ribosometranscription -- ribosome

NB: neuronal cell bodyNB: neuronal cell body NS: Nissl substanceNS: Nissl substance

NL: nucleolusNL: nucleolus BB: Barr bodyBB: Barr body

MurrayLlewellyn

Barr 1908-1995

MurrayLlewellyn

Barr 1908-1995

Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)

Cytoplasmic OrganellesCytoplasmic Organelles

ŸŸ Nissl substance: Nissl substance: rERrER abundant, parallally arranged rER cisternaabundant, parallally arranged rER cisterna

active site of active site of protein (polypeptide)protein (polypeptide) synthesis synthesis

- - transport vesicletransport vesicle

ŸŸ Golgi complexGolgi complex complex of perinuclear Golgi substancecomplex of perinuclear Golgi substance glycosylation, sulfation & phosphorylationglycosylation, sulfation & phosphorylation

packing and condensation protein to transportpacking and condensation protein to transport

Camilio Golgi

(1843-1926)

Golgi apparatus

Golgi method

(Golgi’s metallic impregnation)

Golgi type I & II cell

Golgi tendon organ

Golgi-Mazzoni corpuscle

Camilio Golgi

(1843-1926)

Golgi apparatus

Golgi method

(Golgi’s metallic impregnation)

Golgi type I & II cell

Golgi tendon organ

Golgi-Mazzoni corpuscle

Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)

Protein Synthesizing AssemblyProtein Synthesizing Assembly

ŸŸ Euchromatic NucleusEuchromatic Nucleus ------- mRNA transcription------- mRNA transcription

ŸŸ Prominent NucleolusProminent Nucleolus ------- rRNA (ribosome) synthesis------- rRNA (ribosome) synthesis

ŸŸ Nissl substance:Nissl substance: rERrER ------- polypeptide chain------- polypeptide chain

ŸŸ Golgi complexGolgi complex ----- ----- destined to transportdestined to transport

-- no protein synthesizing assembly in axonno protein synthesizing assembly in axon - neurotransmitters, enzymes, membrane proteins- neurotransmitters, enzymes, membrane proteins - transport via axonal (axoplasmic) transport- transport via axonal (axoplasmic) transport

Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)

Other Cytoplasmic OrganellesOther Cytoplasmic Organelles

ŸŸ Mitochondria Mitochondria - - energy source for energy source for ion exchangeion exchange (Na (Na++-K-K++ exchange pump) exchange pump) and and axonal transportaxonal transport

ŸŸ LysosomeLysosome - hydrolytic enzymes --- waste products- hydrolytic enzymes --- waste products - lysosomal storage disease (mental retardation, seizure)- lysosomal storage disease (mental retardation, seizure)

Pigment GranulesPigment Granules

Lipofuscin granuleLipofuscin granule, , Melanin granuleMelanin granule

PigmentsPigmentsPigmentsPigments

lipofuscinlipofuscinmelaninmelanin

Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)

Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)Neuronal Cell Body (Soma)

CytoskeletonCytoskeleton

ŸŸ Neurofilament: Intermediate Filament Neurofilament: Intermediate Filament - supporting- supporting

- neurofibril -------- neurofibril ------- reduced silver stainingreduced silver staining

Fink-Heimer methodFink-Heimer method

ŸŸ MicrotubuleMicrotubule - tubulin- tubulin - fast anterograde axonal transport and- fast anterograde axonal transport and retrograde axonal transportretrograde axonal transport

cf. microfilament:cf. microfilament: actin, postsynaptic membraneactin, postsynaptic membrane

CytoskeletonCytoskeleton

NeurofilamentNeurofilament

MicrotubuleMicrotubule

Neurofibril - Neurofibril - neurofilamentneurofilament

Distinction between Axon and DendritesDistinction between Axon and DendritesDistinction between Axon and DendritesDistinction between Axon and Dendrites

Axon Axon Dendrite Dendrite

DimensionDimensionnumbernumber 11 multiple (0, 1, or more)multiple (0, 1, or more)lengthlength 200 200 m – 1 mm – 1 m less than 700 less than 700 m mdiameterdiameter constant throughoutconstant throughout gradually tapered gradually tapered

Branching patternBranching patternangleangle almost right anglealmost right angle acute angle acute anglesitesite distant from cell bodydistant from cell body near cell body near cell body

Structural componentsStructural componentsNissl substanceNissl substance absentabsent could be present could be presentdendritic spinedendritic spine absentabsent could be present could be presentmyelin sheathmyelin sheath could be associatedcould be associated not associated not associated

DendriteDendrite

NisslNissl

dendritic spinedendritic spine

Distinction between Axon and DendritesDistinction between Axon and DendritesDistinction between Axon and DendritesDistinction between Axon and Dendrites

Axon Axon Dendrite Dendrite

Staining propertyStaining property GolgiGolgi hard to impregnatehard to impregnate well delineated well delineated impregnation impregnation (except rapid Golgi method)(except rapid Golgi method)

reduced silverreduced silver more darkly stainedmore darkly stained less darkly stained less darkly stained

FunctionalFunctional direction ofdirection of efferent efferent afferent afferent conductionconduction (soma (soma → axon terminal) (dendrite → soma)→ axon terminal) (dendrite → soma)

exception: pseudounipolar neuronexception: pseudounipolar neuron

Golgi methodGolgi method

Reduced silver methodReduced silver method

SYNAPSESYNAPSESYNAPSESYNAPSE

ŸŸ Presynaptic Portion: Synaptic Button Presynaptic Portion: Synaptic Button - synaptic vesicle- synaptic vesicle

- mitochondria- mitochondria - presynaptic membrane: tubulin- presynaptic membrane: tubulin

ŸŸ Synaptic Cleft Synaptic Cleft - 20-30 nm- 20-30 nm

ŸŸ Postsynaptic PortionPostsynaptic Portion - postsynaptic membrane: actin, fodrin, spectrin- postsynaptic membrane: actin, fodrin, spectrin

- mitochondria- mitochondria

SYNAPSESYNAPSESYNAPSESYNAPSE

SYNAPSESYNAPSE

Components of Axonal (Axoplasmic) TransportComponents of Axonal (Axoplasmic) Transport

Components Velocity (mm/day) Transporting SubstancesComponents Velocity (mm/day) Transporting Substances

Anterograde Axonal TransportAnterograde Axonal Transport Fast Transport Fast Transport 200-400200-400 synaptic vesicle, enzymes neurotransmitters Mitochondrial Transport 50-10050-100 mitochondria

Slow TransportSlow Transport

Slow Components a (SCa) 0.1 - 1.00.1 - 1.0 tubulin, neurofilament protein Slow Comnponent b (SCb) 2 - 62 - 6 actin, clathrine, calmodulins spectrin, cytoplasmic enzymes Retrograde Axonal Transport Retrograde Axonal Transport 100-200100-200 prelysosomal vesicles, recycled proteins, HRP, WGA neurotrophic viruses

Axonal (Axoplasmic) TransportAxonal (Axoplasmic) TransportAxonal (Axoplasmic) TransportAxonal (Axoplasmic) Transport

Mechanism ofMechanism of Axonal Axonal TransportTransport

FastFast AnterogradeAnterograde Axonal transportAxonal transport

andand

RetrogradeRetrograde Axonal transportAxonal transport

Mechanism ofMechanism of Axonal Axonal TransportTransport

FastFast AnterogradeAnterograde Axonal transportAxonal transport

andand

RetrogradeRetrograde Axonal transportAxonal transport

Degeneration and RegenerationDegeneration and Regenerationof Nervous Systemof Nervous System

Degeneration and RegenerationDegeneration and Regenerationof Nervous Systemof Nervous System

1. Wallerian Degeneration1. Wallerian Degeneration - changes distal to the injury site- changes distal to the injury site - myelin breakdown- myelin breakdown - von B- von Büüngnerngner’’s band - Schwann cells band - Schwann cell - neuroma formation- neuroma formation

2. Axon Reaction (Chromatolysis, 2. Axon Reaction (Chromatolysis, Nissl Reaction)Nissl Reaction) - displacement of nucleus- displacement of nucleus - chromatolysis- chromatolysis - regenerative processes- regenerative processes

Augustus Waller (1816-1870) Augustus Waller (1816-1870)

Wallerian degenerationWallerian degeneration

Axon (Nissl) Reaction - chromatolysis Axon (Nissl) Reaction - chromatolysis Axon (Nissl) Reaction - chromatolysis Axon (Nissl) Reaction - chromatolysis

Tract Tracing MethodsTract Tracing MethodsTract Tracing MethodsTract Tracing Methods

1) retrograde tracing methods1) retrograde tracing methods

axon, axon terminal axon, axon terminal cell body cell body

2) anterograde tracing methods2) anterograde tracing methods

cell body cell body axon, axon terminal axon, axon terminal

cell body ---- axon terminalcell body ---- axon terminal

based on based on nerve degenerationnerve degeneration and and axonal transportaxonal transport

1. Nissl Reaction1. Nissl Reaction

methylene blue, toluidine blue,methylene blue, toluidine blue,

thionin, cresyl violetthionin, cresyl violet

2. Retrograde Tracer2. Retrograde Tracer

Horseradish Peroxidase (HRP)Horseradish Peroxidase (HRP)

Wheat-germ Agglutinin (WGA) Wheat-germ Agglutinin (WGA)

Fluorescence TracerFluorescence Tracer

- Lucifer Yellow, Fast Blue, Nuclear Yellow- Lucifer Yellow, Fast Blue, Nuclear Yellow

Viruses and ToxoidsViruses and Toxoids

Retrograde Tracing MethodsRetrograde Tracing MethodsRetrograde Tracing MethodsRetrograde Tracing Methods

Retrograde Labeling of HRPRetrograde Labeling of HRP Retrograde Labeling of HRPRetrograde Labeling of HRP

1. Marchi Method1. Marchi Method OsO4 after tract of nerve lesionOsO4 after tract of nerve lesion

2. Nauta Method - Fink Heimer method2. Nauta Method - Fink Heimer method

Reduced Silver Method after tract lesionReduced Silver Method after tract lesion

3. Autoradiograhy with Radiolabelled Amino Acid3. Autoradiograhy with Radiolabelled Amino Acid

Tritiated Glycine Tritiated Glycine

4. Anterograde Tracer4. Anterograde Tracer

Phageolus Vulgaris Leucoagglutinin (PHA-L)Phageolus Vulgaris Leucoagglutinin (PHA-L)

Anterograde Tracing MethodsAnterograde Tracing MethodsAnterograde Tracing MethodsAnterograde Tracing Methods

Marchi method - Wallerian degeneration Marchi method - Wallerian degeneration Marchi method - Wallerian degeneration Marchi method - Wallerian degeneration

Nauta methodNauta method

Reduced silver methodReduced silver method

after axon transectionafter axon transection

neurofilamentneurofilament transport transport

continues after axoncontinues after axon

transectiontransection

Nauta-GygaxNauta-Gygax method method

Fink-HeimerFink-Heimer method method

33H-labeled amino acidH-labeled amino acid

AutoradiographyAutoradiography

Amino acid is incorporatedAmino acid is incorporated

to protein in neuronal to protein in neuronal

cell bodies cell bodies

Proteins are slowly Proteins are slowly

transported to axonaltransported to axonal

endingsendings

Classification of NeuronsClassification of NeuronsClassification of NeuronsClassification of Neurons

(1) by the Number of Processes(1) by the Number of Processes 1. unipolar neuron1. unipolar neuron 2. pseudounipolar neuron2. pseudounipolar neuron 3. bipolar neuron3. bipolar neuron 4. multipolar neuron4. multipolar neuron

(2) by the Length of Axon(2) by the Length of Axon 1. Golgi type I neuron1. Golgi type I neuron 2. Golgi type II neuron2. Golgi type II neuron

(3) by the Morphology of Dendrites(3) by the Morphology of Dendrites (Topognostic Value)(Topognostic Value) 1. isodendritic neuron1. isodendritic neuron 2. allodendritic neuron2. allodendritic neuron 3. idiodendritic neuron3. idiodendritic neuron

1. unipolar neuron 2. bipolar neuron

3. pseudounipolar neuron 4. multipolar neuron

a. axon d. dendrite

1. unipolar neuron 2. bipolar neuron

3. pseudounipolar neuron 4. multipolar neuron

a. axon d. dendrite

Pseudounipolar NeuronPseudounipolar Neuron

DRG (dorsal root ganglion) neuronDRG (dorsal root ganglion) neuron

pseudounipolar cellpseudounipolar cell

peripheralperipheralprocessprocess

centralcentralprocessprocess

telodendrontelodendrontelodendrontelodendron

cell body cell body in DRGin DRG

Neuroglia (Neuroglial Cells)Neuroglia (Neuroglial Cells)Neuroglia (Neuroglial Cells)Neuroglia (Neuroglial Cells)

Central NeurogliaCentral Neuroglia AstrocyteAstrocyte protoplasmic astrocyteprotoplasmic astrocyte fibrous astrocytefibrous astrocyte

OligodendrocyteOligodendrocyte perineuronal satellite cellperineuronal satellite cell interfascicular cellinterfascicular cell

MicrogliaMicroglia Ependymal CellEpendymal Cell

Peripheral NeurogliaPeripheral Neuroglia Schwann CellSchwann Cell

in peripheral nervein peripheral nerve

and ganglionand ganglion

Capsular (Satellite) CellCapsular (Satellite) Cell

in ganglionin ganglion

AstrocyteAstrocyte Oligodendrocyte Oligodendrocyte Microglia Microglia

Central NeurogliaCentral NeurogliaCentral NeurogliaCentral Neuroglia

AstrocyteAstrocyteAstrocyteAstrocyte

• Protoplasmic Astrocyte: Gray Matter Protoplasmic Astrocyte: Gray Matter • Fibrous Astrocyte: White MatterFibrous Astrocyte: White Matter

Cell BodyCell Body ‘‘potatopotato’’ shape nucleus, scarse pale cytopasm shape nucleus, scarse pale cytopasm

ProcessesProcesses - - GFAP GFAP (glial fibroacidic protein):(glial fibroacidic protein): intermediate filament intermediate filament

-- Perivascular Feet Perivascular Feet (Foot Process, Vascular End-Feet)(Foot Process, Vascular End-Feet) surrounding blood vesselssurrounding blood vessels

Specialized AstrocytesSpecialized Astrocytes

- Bergmann- Bergmann’’s gial cell, Muller cell, pituicytes gial cell, Muller cell, pituicyte

ProtoplasmicProtoplasmic Fibrous Fibrous Synaptic Synaptic

AstrocyteAstrocyte AstrocyteAstrocyte Glomerulus Glomerulus

OligodendrocyteOligodendrocyteOligodendrocyteOligodendrocyte

• Perineuronal Satellite Cell Perineuronal Satellite Cell • Interfascicular CellInterfascicular Cell

Cell BodyCell Body round, heterochromatic nucleusround, heterochromatic nucleus dark cytopasmdark cytopasm - rER, free ribosome, Golgi complex, mitochondria- rER, free ribosome, Golgi complex, mitochondria

Myelin forming cell in CNSMyelin forming cell in CNS - - Myelin SheathMyelin Sheath

Each process constitutes a Each process constitutes a internodal segmentinternodal segment

Oligodendrocyte

1. nucleus of

oligodendrocyte

2. process of

oligodendrocyte

3. myelin sheath

4. axon

Oligodendrocyte

1. nucleus of

oligodendrocyte

2. process of

oligodendrocyte

3. myelin sheath

4. axon

MicrogliaMicrogliaMicrogliaMicroglia

Cell BodyCell Body slender, indented, heterochromatic nucleusslender, indented, heterochromatic nucleus dark cytopasmdark cytopasm - prominent secondary lysosome- prominent secondary lysosome

ProcessesProcessesshort, highly branchedshort, highly branched

Macrophage (Mononuclear Phagocytic) SystemMacrophage (Mononuclear Phagocytic) SystemMesenchymal Origin - Blood MonocyteMesenchymal Origin - Blood MonocyteIncreased inIncreased in Inflammation Inflammation

Microglia

1. nucleus of

microglia

2. process of

microglia

3. lysosome

4. capillary

5. pericyte

Microglia

1. nucleus of

microglia

2. process of

microglia

3. lysosome

4. capillary

5. pericyte

Ependymal CellEpendymal CellEpendymal CellEpendymal Cell

Epithelial Cell Epithelial Cell lining ventricular surfacelining ventricular surface cilia and microvilli on luminal surfacecilia and microvilli on luminal surface simple cuboidal cell with round nucleussimple cuboidal cell with round nucleus

TanicyteTanicytebasal process, numerous in 3rd ventriclebasal process, numerous in 3rd ventriclemost ependymal cell has basal processmost ependymal cell has basal process (Chung & Lee, 1988)(Chung & Lee, 1988)

Choroid Plexus Epithelial CellsChoroid Plexus Epithelial Cellsion transporting cell: numerous mitochondriaion transporting cell: numerous mitochondria

Schwann CellSchwann CellSchwann CellSchwann Cell

Slender Cell Slender Cell with small heterochromatic nucleiwith small heterochromatic nuclei

Myelin forming cell in PNSMyelin forming cell in PNS - - Myelin Sheath: Myelin Sheath: Myelinated FiberMyelinated Fiber

A Schwann cell constitutes a internodal SegmentA Schwann cell constitutes a internodal Segment

Surround Surround Unmyelinated AxonsUnmyelinated Axons A schwann cell surround A schwann cell surround

many unmyelinated axonsmany unmyelinated axons

Schwann CellSchwann Cell

Satellite (Capsular) CellSatellite (Capsular) CellSatellite (Capsular) CellSatellite (Capsular) Cell

Squamous Cell encircles Squamous Cell encircles neuronal cell bodyneuronal cell body

in Ganglion in Ganglion

- completely encircles pseudounipolar neuron- completely encircles pseudounipolar neuron

in in spinal and cranial ganglionspinal and cranial ganglion

- neurons of autonomic ganglia were - neurons of autonomic ganglia were

less completely surrounded by satellite cellless completely surrounded by satellite cell

Myelin Sheath - MYELINMyelin Sheath - MYELIN cf. Schwann sheath, Neurilemmacf. Schwann sheath, Neurilemma

• formed by wrapped plasma membrane offormed by wrapped plasma membrane of OligodendrocyteOligodendrocyte in CNS in CNS Schwann CellSchwann Cell in PNS in PNS

• Node of RanvierNode of Ranvier - Saltatory Conduction - Saltatory Conduction evolutionary innovation in chordateevolutionary innovation in chordate - - conduction velocityconduction velocity

MyelinMyelinMyelinMyelin

MyelinMyelinMyelinMyelin

Node of Ranvier - Internodal segmentNode of Ranvier - Internodal segmentSchmidt-LantermannSchmidt-Lantermann’’s clefts cleft

Osmium tetroxide (OsOOsmium tetroxide (OsO44)) stain for Myelinstain for Myelin

MyelinMyelin

Structure of fast nerve conductionStructure of fast nerve conduction

Giant squid axon 0.5-1 mm in diameterGiant squid axon 0.5-1 mm in diameter

conduction velocity 25 m/sconduction velocity 25 m/s

MyelinMyelinMyelinMyelin

Conduction velocityConduction velocity is proportional to is proportional to

1. The Length of Internodal Segment1. The Length of Internodal Segment

2. Thickness of Myelin2. Thickness of Myelin

3. Diameter of Nerve Fiber3. Diameter of Nerve Fiber

Conduction velocity of Conduction velocity of

mammalian nerve fibermammalian nerve fiber

Group IGroup I AA 10 - 20 10 - 20 70 -120 70 -120

Group IIGroup II AA 5 - 12 5 - 12 30 - 70 30 - 70

AAγγ 3 - 6 3 - 6 15 - 30 15 - 30

Group IIIGroup III AAδδ 2 - 5 2 - 5 12 - 30 12 - 30

BB < 3 < 3 3 - 15 3 - 15

Group IVGroup IV CC 0.1 - 1.5 0.1 - 1.5 0.5 - 20.5 - 2

Myelinated fiberMyelinated fiber

Unmyelinated fiberUnmyelinated fiber

Myelin FormationMyelin FormationMyelin FormationMyelin Formation

MyelinMyelinMyelinMyelin

MyelinMyelinformationformation

Schwann cellSchwann celloligodendrocyteoligodendrocyte

MYELIN - Fusion of Plasma MembraneMYELIN - Fusion of Plasma Membrane Major Dense LineMajor Dense Line - fusion of inner leaflet - fusion of inner leaflet ---- Myelin Basic Protein (MBP)---- Myelin Basic Protein (MBP)

Intraperiod LineIntraperiod Line - fusion of outer leaflet - fusion of outer leaflet ---- Proteolipid Protein (PLP)---- Proteolipid Protein (PLP)

in oligodendrocytein oligodendrocyte ---- Protein Zero (P---- Protein Zero (P00) )

in Schwann Cellin Schwann Cell

MyelinMyelinMyelinMyelin

MyelinMyelinMyelinMyelin

1. trilaminar unit membrane1. trilaminar unit membrane 2. major dense line 2. major dense line

3. intraperiod line3. intraperiod line 4. Cytoplasm of Schwann cell 4. Cytoplasm of Schwann cell

Multiple Slerosis Multiple Slerosis – disease of the myelin– disease of the myelin

Jacqueline Du PreJacqueline Du PreJacqueline Du PreJacqueline Du Preoligodendrocyteoligodendrocyte

LEPROSY:LEPROSY: Mycobactrium lepraeMycobactrium leprae infection ofinfection of Schwann cellSchwann cell

Rembrandt. Rembrandt. The King Uzziah Stricken with Leprosy. The King Uzziah Stricken with Leprosy.

Organization of Nervous SystemOrganization of Nervous SystemOrganization of Nervous SystemOrganization of Nervous System

Central Nervous SystemCentral Nervous System

Gray MatterGray Matter Nucleus and CortexNucleus and Cortex White MatterWhite Matter TractsTracts

Peripheral Nervous SystemPeripheral Nervous System

Nerve (Peripheral Nerve)Nerve (Peripheral Nerve) GanglionGanglion

Peripheral NervePeripheral Nerve

Nerve FiberNerve Fiber

Myelinated Nerve Fiber Myelinated Nerve Fiber

Axon,Axon, Myelin sheathMyelin sheath, Schwann cell, Schwann cell

Unmyelinated Nerve Fiber Unmyelinated Nerve Fiber Axon, Schwann cellAxon, Schwann cell

Connective Tissue SheathConnective Tissue Sheath

EndoneuriumEndoneurium Perineurium – blood vesselsPerineurium – blood vessels EpineuriumEpineurium

Composition of Peripheral NerveComposition of Peripheral NerveComposition of Peripheral NerveComposition of Peripheral Nerve

Composition of Peripheral NerveComposition of Peripheral NerveComposition of Peripheral NerveComposition of Peripheral Nerve

Peripheral Nerve Endings:Peripheral Nerve Endings:Afferent EndingsAfferent Endings

RReceptor Neurons of Craniospinal Ganglioneceptor Neurons of Craniospinal Ganglion

ŸŸpseudounipolar neurons of dorsal root gangliapseudounipolar neurons of dorsal root ganglia

ŸŸ trigeminal (semilunar, Gasserian ganglion), trigeminal (semilunar, Gasserian ganglion), geniculate (VII), superior IX, superior X ganglia (GSA)geniculate (VII), superior IX, superior X ganglia (GSA)

ŸŸgeniculate (VII), inferior IX, inferior X ganglia (VA)geniculate (VII), inferior IX, inferior X ganglia (VA)

Morphological ClassificationMorphological Classification

ŸŸ free nerve endingsfree nerve endings

ŸŸ expanded tip endings expanded tip endings

ŸŸ encapsulated endings encapsulated endings ----- CT envestment----- CT envestment

Afferent EndingsAfferent Endings

Free Nerve EndingsFree Nerve Endings

- Nerve endings without special structural- Nerve endings without special structural

organizationorganization

- - pain and temperaturepain and temperature receptor receptor

Expanded Tip EndingsExpanded Tip Endings

- - MerkelMerkel’’s Touch Corpuscles Touch CorpuscleMerkel cells in basal layer of epidermisMerkel cells in basal layer of epidermis

- - Type I Hair cellsType I Hair cells of Vestibular Labyrinth of Vestibular Labyrinth

Afferent EndingsAfferent Endings

Encapsulated EndingsEncapsulated Endings

- Meissner- Meissner’’s Corpuscles Corpuscle

- Pacinian Corpuscle- Pacinian Corpuscle

(Corpuscle of Vater-Pacini)(Corpuscle of Vater-Pacini)

- Genital Corpuscle- Genital Corpuscle

- Ruffini- Ruffini’’s Endings Ending

- End Bulb of Krause- End Bulb of Krause

- - Golgi tendon organ:Golgi tendon organ: ProprioceptorProprioceptor

Receptor Receptor

EndingsEndings

ŸŸ Free nerve Free nerve endingending

ŸŸ Expanded Expanded tip endingtip ending

ŸŸ Encapsulated Encapsulated endingending

MerkelMerkel’’s s

Touch CorpuscleTouch Corpuscle

ŸŸ expanded tip endingexpanded tip ending

ŸŸ Merkel cell Merkel cell - clear cell located in the- clear cell located in the

basal layer of epidermisbasal layer of epidermis

- membrane bound electron - membrane bound electron

dense granules resemblesdense granules resembles

synaptic vesiclesynaptic vesicle

MeissnerMeissner’’s Corpuscles Corpuscle

Pacinian CorpusclePacinian Corpuscle

Other Encapsulated EndingsOther Encapsulated Endings

End Bulb of KrauseEnd Bulb of Krause Genital Corpuscle Lingual CorpuscleGenital Corpuscle Lingual Corpuscle

Efferent EndingsEfferent Endings

Somatic Efferent EndingsSomatic Efferent Endings

Neuromuscular JunctionNeuromuscular Junction (Myoneural Junction, Motor End Plate)(Myoneural Junction, Motor End Plate)

Autonomic Efferent EndingsAutonomic Efferent Endings

Endings on smooth muscle Endings on smooth muscle

and blood vessels and blood vessels

Somatic Efferent EndingsSomatic Efferent Endings

Neuromuscular JunctionNeuromuscular Junction (Myoneural Junction, Motor End Plate)(Myoneural Junction, Motor End Plate)

Autonomic Efferent EndingsAutonomic Efferent Endings

Endings on smooth muscle Endings on smooth muscle

and blood vessels and blood vessels

NeuromuscularNeuromuscularJunctionJunction

(Myoneural Junction,(Myoneural Junction,

Motor End Plate)Motor End Plate)

NeuromuscularNeuromuscularJunctionJunction

(Myoneural Junction,(Myoneural Junction,

Motor End Plate)Motor End Plate)

NMJNMJNMJNMJ

MM

NN

Neuromuscular JunctionNeuromuscular Junction

(Motor End Plate)(Motor End Plate)Neuromuscular JunctionNeuromuscular Junction

(Motor End Plate)(Motor End Plate)

Myasthenia GravisMyasthenia GravisMyasthenia GravisMyasthenia Gravis

• muscle weaknessmuscle weakness which is greatly which is greatly increased by exertion or increased by exertion or repeated contractionrepeated contraction

• autoimmune disease autoimmune disease with autoantibodieswith autoantibodies against against Ach receptorAch receptor

• maybe fatal if untreatedmaybe fatal if untreated by respiratory paralysisby respiratory paralysis

• treated withtreated with AchT inhibitorsAchT inhibitors, , thymectomy, and thymectomy, and corticosteroidscorticosteroids

Defects in NMDefects in NM

TransmissionTransmission

before treatment after treatmentbefore treatment after treatment

Autonomic Efferent EndingsAutonomic Efferent EndingsAutonomic Efferent EndingsAutonomic Efferent Endings

Neuromuscular SpindleNeuromuscular Spindle

• Both receptor and effectorBoth receptor and effector

• StructureStructure

1. Capsule1. Capsule

2. Intrafusal Muscle Fibers2. Intrafusal Muscle Fibers

- Nuclear Bag Fiber- Nuclear Bag Fiber - Nuclear Chain Fiber- Nuclear Chain Fiber

3. Receptor and Effector Nerve Endings3. Receptor and Effector Nerve Endings

- Afferent Ending- Afferent Ending - Efferent Ending- Efferent Ending

NB: nuclear bag fiber NB: nuclear bag fiber IF: intrafusal muscle fiberIF: intrafusal muscle fiber

CA: capsule CA: capsule EF: extrafusal muscle fiberEF: extrafusal muscle fiber

Neuromuscular SpindleNeuromuscular Spindle

• INTRAFUSAL MUSCLE FIBERSINTRAFUSAL MUSCLE FIBERS

(1) Nuclear Bag Fiber(1) Nuclear Bag Fiber

- 1-4 / each spindle- 1-4 / each spindle

- longer and thicker than nuclear chain fiber- longer and thicker than nuclear chain fiber

- large central aggregation of nucleus in- large central aggregation of nucleus in

equatorial regionequatorial region

(2) Nuclear Chain Fiber(2) Nuclear Chain Fiber - many fibers / spindle- many fibers / spindle - smaller and thinner than nuclear bag fiber- smaller and thinner than nuclear bag fiber - central row of nucleus in equatorial region- central row of nucleus in equatorial region

Neuromuscular SpindleNeuromuscular Spindle

INNERVATIONINNERVATION

Afferent Fibers: ProprioceptorsAfferent Fibers: Proprioceptors

(1) Primary (Annulospiral) Endings(1) Primary (Annulospiral) Endings

- Group Ia (12-20 - Group Ia (12-20 m in diameter) afferentsm in diameter) afferents

- terminate in both NB and NC fibers- terminate in both NB and NC fibers

- wound around the central equatorial region- wound around the central equatorial region

(2) Secondary (Flower-Spray) Endings(2) Secondary (Flower-Spray) Endings - group II (6-8 - group II (6-8 m in diameter) afferentm in diameter) afferent - terminates predominantly in nuclear chain fiber- terminates predominantly in nuclear chain fiber - terminates around juxtaequatorial region- terminates around juxtaequatorial region

Neuromuscular SpindleNeuromuscular Spindle

• INNERVATIONINNERVATION

Efferent FibersEfferent Fibers

Gamma (Gamma () Motor Fiber) Motor Fiber

- terminates in small motor end plates- terminates in small motor end plates

of the non-nucleated (striated) regionof the non-nucleated (striated) region

of both intrafusal muscle fibers of both intrafusal muscle fibers