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8/3/2019 Topic 3 (Neurons and Glia July 2010)
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NEURONS AND GLIANEURONS AND GLIA
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BIO616BIO616 Neurons and GliaNeurons and Glia 22
LEARNING OBJECTIVESEARNING OBJECTIVESAt the end of this topic students should beAt the end of this topic students should be
able to:able to: discuss the difference between neurons anddiscuss the difference between neurons and
gliaglia discuss the structure of neurons and gliadiscuss the structure of neurons and glia Discuss the different techniques of stainingDiscuss the different techniques of staining
nerve cellsnerve cells discuss the functions of neurons and gliadiscuss the functions of neurons and glia discuss the neuron doctrinediscuss the neuron doctrine classify different types of neuronsclassify different types of neurons
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BIO616BIO616 Neurons and GliaNeurons and Glia 33
LEARNING OUTCOMESEARNING OUTCOMESAt the end of this topic students must be able to:At the end of this topic students must be able to: differentiate between different histologicaldifferentiate between different histological
techniques used to differentiate different parts oftechniques used to differentiate different parts ofneuronsneurons
draw and correctly label a typical neurondraw and correctly label a typical neuron state and discuss the functions of neuronsstate and discuss the functions of neurons state and discuss the functions of gliastate and discuss the functions of glia name the different types of glianame the different types of glia
Correctly classify neurons based on structure, neuralCorrectly classify neurons based on structure, neuralconnections, axonal length and types ofconnections, axonal length and types ofneurotransmitterneurotransmitter
Discuss the concept of neural circuits and state atDiscuss the concept of neural circuits and state atleast one example of a neural circuitleast one example of a neural circuit
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IntroductionntroductionNeurophilosophyNeurophilosophy
Brain is the origin of mental abilitiesBrain is the origin of mental abilities
NeuronsNeurons
Process and transmit informationProcess and transmit information
Sense environmental changesSense environmental changes
Communicate changes to other neuronCommunicate changes to other neuron
Command body responseCommand body response
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Introductionntroduction Glial cellsGlial cells (10-50x more of these than
neurons)
Structural support Maintenance of ionic compositions
Remove extrachemicals (neurotransmitters,) followingtheir release from neurons
Insulate neurons electrically
Formation of blood-brain barrier Secretion of compounds for neuronal maintenance
Participate in information flow in the nervous system
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The Neuron Doctrinehe Neuron Doctrine HistologyHistology
Study of tissueStudy of tissue
structurestructure The Nissl StainThe Nissl Stain
Facilitates the studyFacilitates the study
of cytoarchitecture inof cytoarchitecture in
the CNSthe CNS
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The Neuron Doctrinehe Neuron DoctrineNISSLBODIES
NEURONS
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The Neuron Doctrinehe Neuron Doctrine Silver nitrate stainSilver nitrate stain
Stains random neuronsStains random neurons
Discovered by Golgi (1873) inDiscovered by Golgi (1873) in
a kitchen workinga kitchen working bybycandlelightcandlelight
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Camillo Golgi (1843-1926)
Purkinje cell(cerebellum)
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The Neuron Doctrinehe Neuron Doctrine Golgi-stain shows twoGolgi-stain shows two
parts of neurons:parts of neurons: Cell body, soma orCell body, soma or
perikaryonperikaryon
Neurites: Axons andNeurites: Axons anddendritesdendrites
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BIO616BIO616 Neurons and GliaNeurons and Glia 1010
The Neuron Doctrinehe Neuron Doctrine Cell bodyCell body
The expended portion of the neuron that contains nucleusThe expended portion of the neuron that contains nucleus Stains basophilically due to the abundance of RER andStains basophilically due to the abundance of RER and
polyribosomespolyribosomes
The clumps of RER and polyribosomes are referred to asThe clumps of RER and polyribosomes are referred to asNissl BodiesNissl Bodies DendritesDendrites
One to many extensions of the cell bodyOne to many extensions of the cell body Specialized to receive input from other neurons or fromSpecialized to receive input from other neurons or from
receptorsreceptors
Contain Nissl bodies in their proximal parts and thus theContain Nissl bodies in their proximal parts and thus theinitial portions of dendrites stain basophilicallyinitial portions of dendrites stain basophilically
Often have small protrusions, called dendritic spines, thatOften have small protrusions, called dendritic spines, thatexpand the dendritic surface area and serve as sites ofexpand the dendritic surface area and serve as sites ofsynaptic contantsynaptic contant
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BIO616BIO616 Neurons and GliaNeurons and Glia 1111
The Neuron Doctrinehe Neuron Doctrine Golgi silver stain: neuron from theGolgi silver stain: neuron from the
cerebellumcerebellum
CELL BODYENDRITES
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The Neuron Doctrinehe Neuron Doctrine Neurons: Continuous or contiguous?Neurons: Continuous or contiguous?
Fused neural networks or independent?Fused neural networks or independent?
If fused How can there be localizationIf fused How can there be localizationof function as suggested by Brocasof function as suggested by Brocas
finding?finding?
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The Neuron Doctrinehe Neuron Doctrine Cajals ContributionCajals Contribution
Neural circuitryNeural circuitry
Neurons communicateNeurons communicateby contact, notby contact, not
continuitycontinuity
Neuron doctrineNeuron doctrine Neurons adhere to cellNeurons adhere to cell
theorytheory
Santiago Ramon y Cajal(1852-1934)
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The great debate what units make uphe great debate what units make upthe brain?he brain?Camillo Golgiamil lo Golgi Santiago Ramon y Cajalantiago Ramon y CajalInvented Golgi technique ofInvented Golgi technique of Used the Golgi method on brainUsed the Golgi method on brain tissuetissue
examining brain tissueexamining brain tissue
Argued fervently (and correctly)Argued fervently (and correctly) thatthat
Argued fervently (andArgued fervently (and neurons are single cellsneurons are single cells
incorrectly) that the brainincorrectly) that the brain
is ais a network, or reticulum, ofnetwork, or reticulum, of Guessed correctly at the directionGuessed correctly at the direction
connected cellsconnected cells of information flow within theof information flow within the
nervous system, judging by cellnervous system, judging by cell structurestructure
Discovered the Golgi apparatusDiscovered the Golgi apparatus
and the Golgi stretch receptorand the Golgi stretch receptor Described many cell types inDescribed many cell types in many brainmany brain
structures, including developing neuronsstructures, including developing neurons
Neuron doctrineNeuron doctrine
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The great debate what unitshe great debate what unitsmake up the brain?ake up the brain? The two men disagreed up to theThe two men disagreed up to the
death of Golgi 10 years before Cajaldeath of Golgi 10 years before Cajal
They also shared the Nobel prize inThey also shared the Nobel prize in19061906
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Neurons and GliaNeurons and Glia
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Neurons and GliaNeurons and Glia
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The Prototypical Neuronhe Prototypical Neuron Neuronal membraneNeuronal membrane
The cell body (soma)The cell body (soma) Contains nucleus & organelles common
functions Mainly found in CNS Cytosol: Watery fluid inside the cellCytosol: Watery fluid inside the cell
Organelles: Membrane-enclosed structures withinOrganelles: Membrane-enclosed structures withinthe somathe soma Cytoplasm: Contents within a cell membraneCytoplasm: Contents within a cell membrane
(e.g., organelles, excluding the nucleus)(e.g., organelles, excluding the nucleus)
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Neurons and GliaNeurons and Glia
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The Prototypical Neuronhe Prototypical Neuron The SomaThe Soma
Gene expressionGene expression
Protein synthesisProtein synthesis
RNA splicingRNA splicing
Molecular biologyMolecular biology
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The Prototypical Neuronhe Prototypical Neuron The SomaThe Soma
Rough EndoplasmicRough Endoplasmic
Reticulum (ER)Reticulum (ER) Major site for proteinMajor site for protein
synthesissynthesis
Free ribosomesFree ribosomes
PolyribosomesPolyribosomes
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The Prototypical Neuronhe Prototypical Neuron The SomaThe Soma
Rough ERRough ER
Protein synthesis in neuronsProtein synthesis in neurons
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BIO616BIO616 Neurons and GliaNeurons and Glia 2020
The Prototypical Neuronhe Prototypical Neuron The SomaThe Soma
Smooth ER and Golgi ApparatusSmooth ER and Golgi Apparatus
Sites for preparing/sorting proteins forSites for preparing/sorting proteins fordelivery to different cell regions (trafficking)delivery to different cell regions (trafficking)
and regulating substancesand regulating substances
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The Prototypical Neuronhe Prototypical Neuron The SomaThe Soma
MitochondrionMitochondrion
Site of cellularSite of cellularrespiration (inhale andrespiration (inhale and
exhale)exhale)
Krebs cycleKrebs cycle
ATP- cells energyATP- cells energysourcesource
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The Prototypical Neuronhe Prototypical Neuron The Neuronal MembraneThe Neuronal Membrane
Barrier that encloses cytoplasmBarrier that encloses cytoplasm
~5 nm thick~5 nm thick
Protein concentration in membrane variesProtein concentration in membrane varies
Structure of discrete membrane regionsStructure of discrete membrane regions
influences neuronal functioninfluences neuronal function
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The Prototypical Neuronhe Prototypical Neuron The CytoskeletonThe Cytoskeleton
Not staticNot static
Internal scaffolding ofInternal scaffolding ofneuronal membraneneuronal membrane
Three bonesThree bones
MicrotubulesMicrotubules MicrofilamentsMicrofilaments
NeurofilamentsNeurofilaments
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The Prototypical Neuronhe Prototypical NeuronAxon
Forms connection with target (effector)
Conducts impulses away from the cellbody Typically one per neuron Lacks Nissl bodies and does not stain with
routine histological stains
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The Prototypical Neuronhe Prototypical Neuron The AxonThe Axon
Axon hillock (beginning)Axon hillock (beginning)
Axon proper (middle)Axon proper (middle)
Axon terminal (end)Axon terminal (end)
Differences betweenDifferences between
axon and somaaxon and soma
ER does not extend intoER does not extend into
axonaxon
Protein composition:Protein composition:
UniqueUnique
I t Z
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Output ZoneAxon
Terminals
Nucleus
Axon
Cell body
Dendrites
Input Zone
Dendrites
and
Cell body
Trigger Zone
Axon hillock
Conducting Zone
Axon (may be from 1mm
to morethan 1 m long
Arrows indicate the
direction in which nervesignals are conveyed.
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The Prototypical Neuronhe Prototypical Neuron The AxonThe Axon
The Axon TerminalThe Axon Terminal
Differences between the cytoplasm of axonDifferences between the cytoplasm of axonterminal and axonterminal and axon
No microtubules in terminalNo microtubules in terminal
Presence of synaptic vesiclesPresence of synaptic vesicles
Abundance of membrane proteinsAbundance of membrane proteins Large number of mitochondriaLarge number of mitochondria
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The Prototypical Neuronhe Prototypical Neuron The AxonThe Axon
SynapseSynapse
Gap between a synapticGap between a synapticterminal and target cellterminal and target cell Synaptic transmissionSynaptic transmission Electrical-to-chemical-to-Electrical-to-chemical-to-
electrical transformationelectrical transformation Synaptic transmissionSynaptic transmission
dysfunctiondysfunction Mental disordersMental disorders
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The Prototypical Neuronhe Prototypical Neuron The AxonThe Axon
Axoplasmic transportAxoplasmic transport
Anterograde (soma to terminal) vs.Anterograde (soma to terminal) vs.
Retrograde (terminal to soma) transportRetrograde (terminal to soma) transport
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The Prototypical Neuronhe Prototypical Neuron DendritesDendrites
Where incoming fibres make connectionsWhere incoming fibres make connections
Conveys signals to the cell bodyConveys signals to the cell bodyAntennae of neuronsAntennae of neurons
Dendritic treeDendritic tree
Synapse - receptorsSynapse - receptors Dendritic spinesDendritic spines
Postsynaptic (receives signals from axonPostsynaptic (receives signals from axon
terminal)terminal)
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The Prototypical Neuronhe Prototypical Neuron
DENDRITICSPINES
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Classifying Neuronslassifying Neurons A single neuron
on the surfaceof a
microprocessor A cm3 of the
human brain willcontain morethan 50 millionneurons.
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Classifying Neuronslassifying Neurons Structural (Anatomical)Structural (Anatomical)
Classification Based on theClassification Based on theNumber of Neurites (Processes)Number of Neurites (Processes) Unipolar (Psuedounipolar)Unipolar (Psuedounipolar)
Has one neurite thatbifurcates The cell body of this neuronal
type is found in spinal andcranial ganglia
BipolarBipolar Has 2 neurites (relatively rare;
retina of eye and certain cranialganglia)
MultipolarMultipolar Many neurites; typically 1 axon
and 2 or more dendrites (mostcommon type of neuron)
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Classifying Neuronslassifying Neurons Structural ClassificationStructural Classification
Based on Dendritic andBased on Dendritic and
Somatic MorphologiesSomatic Morphologies Stellate cells (star-Stellate cells (star-
shaped) and pyramidalshaped) and pyramidal
cells (pyramid-shaped)cells (pyramid-shaped)
Spiny or aspinousSpiny or aspinous
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Classifying Neuronslassifying Neurons Some lack dendritesSome lack dendrites
altogetheraltogether
Some showSome showdendriticdendritic
arborizations (tree-arborizations (tree-
like arrangement)like arrangement)
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Classifying Neuronslassifying Neurons
FunctionallyFunctionally Motor (Efferent) Related to innervation of muscle, glands
etc. Activation ofthese neurons leads to some
motor event (i.e., contraction of amuscle)
Sensory (Afferent) Related to the transfer of sensory
information (i.e., pain touch, pressure,etc.)
Most synapse with interneurons e.g., neurons of spinal (dorsal root)
ganglia Interneurons
Neither motor or sensory (e.g., neuronsresponsible for the various spinalreflexes)
Synapse only with other neurons
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Comparison of Structuralomparison of StructuralClasses of Neuronslasses of Neurons
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Structuralructural D iversity ofversity ofNeuronsurons
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Classifying Neuronslassifying Neurons Further ClassificationFurther Classification
Based on axonal lengthBased on axonal length
Golgi Type IGolgi Type I Golgi Type IIGolgi Type II
Based on neurotransmitter typeBased on neurotransmitter type e.g., Cholinergic = Acetycholine at synapsese.g., Cholinergic = Acetycholine at synapses
Adrenergic = Adrenaline at synapsesAdrenergic = Adrenaline at synapses
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Simple circuitSimple circuit
Synapse between sensory neurons & motorSynapse between sensory neurons & motor
neurons, resulting in a simpleneurons, resulting in a simple reflexeflex Complex circuitComplex circuit
Such as those associated with most behaviors,Such as those associated with most behaviors,
involve integration by interneurons in the CNSinvolve integration by interneurons in the CNS
Convergent circuitsConvergent circuits Divergent circuitsDivergent circuits
Reverberating circuits (memory storage)Reverberating circuits (memory storage)
Neural Circuitseural Circuits
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Neural Circuitseural Circuits The myotaticThe myotatic
(knee-jerk) spinal(knee-jerk) spinal
reflexreflex
The synapticThe synapticconnections betweenconnections between
thethe sensorysensoryafferentsafferentsand the extensorand the extensor
efferentsefferents areare
excitatoryexcitatory
TheThe interneuronsinterneuronsactivated by theactivated by the
afferentsafferents areare
inhibitoryinhibitory
BIO616BIO616 Neurons and GliaNeurons and Glia 4141
http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2855http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2855http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2435http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2435http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2556http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2556http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2556http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2435http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A28558/3/2019 Topic 3 (Neurons and Glia July 2010)
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Neural Circuitseural Circuits Action potentialAction potential activity measured from each element (activity measured from each element (
afferentsafferents,, efferentsefferents, and, and interneuronsinterneurons) before, during,) before, during,
and after a stimulusand after a stimulus
BIO616BIO616 Neurons and GliaNeurons and Glia 4242
http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2254http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2254http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2435http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2435http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2556http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2556http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2556http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2435http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2263http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A22548/3/2019 Topic 3 (Neurons and Glia July 2010)
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Neural Circuitseural Circuits Intracellular recording ofIntracellular recording of
the potential changesthe potential changes
underlying the synapticunderlying the synaptic
connections of theconnections of themyotaticmyotatic reflexreflex circuitcircuit
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http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2819http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A2819http://www.ncbi.nlm.nih.gov/bookshelf/?book=neurosci&part=A2251&rendertype=def-item&id=A28198/3/2019 Topic 3 (Neurons and Glia July 2010)
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Neural Circuitseural Circuits The three functional classes of neurons are theThe three functional classes of neurons are the
basic constituents of all neural circuitsbasic constituents of all neural circuits After birth, neurons grow, and their connectionsAfter birth, neurons grow, and their connections
are enrichedare enriched Neurons are organized in different ways inNeurons are organized in different ways in
different parts of the NSdifferent parts of the NS The density of cells of different types varies asThe density of cells of different types varies as
wellwell Neural projections, example, the dendrites ofNeural projections, example, the dendrites of
neurons, are enriched through experienceneurons, are enriched through experience
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Neural Circuitseural CircuitsExperiment:Experiment:
Rats from the same litter are divided intoRats from the same litter are divided into
two setstwo setsRat A is placed in regular lab box that isRat A is placed in regular lab box that isclean but otherwise boringclean but otherwise boring
Rat B, is put in a nice cage with toysRat B, is put in a nice cage with toys
After 6 months, the animals are sacrificed,After 6 months, the animals are sacrificed,and their brains studiedand their brains studied
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Neural Circuitseural CircuitsResults:Results:
Rat A, has fewer glial cells than does rat BRat A, has fewer glial cells than does rat B
The neurons in rat A have fewer projections thanThe neurons in rat A have fewer projections thanrat B does: the neurons are not as rich inrat B does: the neurons are not as rich in
projection to other neuronsprojection to other neurons
This demonstrates how experience andThis demonstrates how experience and
interaction with the environment enhance neuralinteraction with the environment enhance neural
developmentdevelopment
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Coordination by clusteroordination by cluster Nerve cell bodies are often arranged intoNerve cell bodies are often arranged into
clustersclusters
Allow coordination of activities by only a part of theAllow coordination of activities by only a part of the
nervous systemnervous system
A nucleuA nucleuss is a cluster of nerve cell bodiesis a cluster of nerve cell bodieswithin the CNS (accumulation of grey matter)within the CNS (accumulation of grey matter)
A ganglion is a cluster of nerve cell bodies inA ganglion is a cluster of nerve cell bodies inthe PNSthe PNS
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Coordination by clusteroordination by cluster
Ganglion cells inthe PNS
Dorsal
RootGanglia
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Coordination by clusteroordination by cluster
Brain nuclei
Brainnuclei
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Supporting cellsupporting cells Do not conduct impulsesDo not conduct impulses Outnumber neurons by 10- 50-Outnumber neurons by 10- 50-
foldfold Neurons in CNSNeurons in CNS
Terminally differentiatedTerminally differentiated Incapable of divisionIncapable of division
Glial cells Certain subtypes possess ability to
divide Of interest in terms of understanding
this ability applicable to neurons?Ability to divide most CNS (brain)
tumors linked to glial cells
50
m
Astrocytes
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Supporting cellsupporting cells The CNS has three types and the PNS
has one Neuroglia in the CNS
AstrocytesAstrocytes
Star-shaped cells that play an active role inbrain function by influencing the activity ofneurons
Clearing and recycling of neurotransmitters Clean up brain debris Transport nutrients (neurotrophins e.g.
neural growth factor) to neurons Hold neurons in place Digest parts of dead neurons Regulate content of extracellular space Contribute to formation of blood brain barrier
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Astrocyte labeled with anti-GFAP antibody
GFAP: glial cell fibrillary acidicprotein
Neuron growing on an astrocyticneuroglia cell
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Supporting cellsupporting cells Fibrous astrocytesFibrous astrocytes
Prevalent in white matterPrevalent in white matter
Higly filamentousHigly filamentous Protoplasmic astrocytesProtoplasmic astrocytes
Abundant in grey matterAbundant in grey matter
Less filamentousLess filamentous
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Supporting cellsupporting cells Neuroglia in the CNS
OligodendrocytesOligodendrocytes The analogue of the Schwann cell in the central
nervous system Form the myelin sheaths that insulate the CNS nerveForm the myelin sheaths that insulate the CNS nerve
processesprocesses
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Stained for galactocerbroside
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Supporting cellsupporting cells Neuroglia in the CNS
MicrogliaMicroglia The smallest of glial cells
Involved in immune responseInvolved in immune responsein CNSin CNS Help clean up debris/dyingHelp clean up debris/dying
cellscells Probably a distinct lineage ofProbably a distinct lineage of
cells from other gliacells from other glia
May be linked to destructionMay be linked to destruction
of myelin-producingof myelin-producing
oligodendrocytesin certainoligodendrocytesin certain
forms of multiple sclerosisforms of multiple sclerosisBIO616BIO616 Neurons and GliaNeurons and Glia 5454
Microglialcells (yellow) ingestbranched oligodendrocytecells(purple) ---the process thought to
occur in multiple sclerosis
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Supporting cellsupporting cells Supporting cells inSupporting cells in
the CNSthe CNS
Ependymal cellsEpendymal cells Epithelial-like cellsthat line the surfacesof the brain(ventricles and thecentral canal of thespinal cord)
form barriersform barriers
betweenbetween
compartments (BBB)compartments (BBB)
Ependymalcells
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Supportingupportingcellsel ls
Supporting cells in the CNSSupporting cells in the CNS
Radial gliaRadial glia
Important during developmentImportant during developmentof the CNSof the CNS
Provide pathways for neuronalProvide pathways for neuronal
growth and targetinggrowth and targeting
In adult: Mller cells (retina);In adult: Mller cells (retina);Bergmann cells (cerebellum) areBergmann cells (cerebellum) are
derived from radial gliaderived from radial glia
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DiI fill of an individual radial gliacell (red) inthe mouse embryonic olfactory bulbcounterstained for tissue architecture (green)
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Supportingupportingcellsel ls Neuroglia in the PNS
Lemmocytes(Schwann cells)Schwann cells) Form the insulating myelinForm the insulating myelin
sheath around axons in thesheath around axons in thePNS (wrap individually aroundPNS (wrap individually around
the shaft of peripheral axons)the shaft of peripheral axons) Composed primarily of lipids The lipid serves as an insulator
thereby speeding thetransmission rate of actionpotentials along the axon
Analogous to oligodendrocytesAnalogous to oligodendrocytes Surround other axons w/oSurround other axons w/oforming myelinforming myelin
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A Schwann cell inculture
electron micrograph showing a Schwanncell (G) surrounding an axonal process (A)
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Supporting cellsupporting cells Myelination of neuronsMyelination of neurons
Occurs when Schwann cells or oligodenrocytes grow around anOccurs when Schwann cells or oligodenrocytes grow around an
axon so their plasma membranes form concentric layersaxon so their plasma membranes form concentric layers
In MS, myelin sheaths deteriorate causing a disruption of nerveIn MS, myelin sheaths deteriorate causing a disruption of nerve
impulse transmission & consequent loss of coordinationimpulse transmission & consequent loss of coordination
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Supporting cellsupporting cells Myelination of neuronsMyelination of neurons
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Oligodendrocyte
Oligo processes forming myelinsheaths on CNS axons
Axon
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Supporting cellsupporting cells Neuroglia in the PNS
Sattelite cells
Important for structure ofImportant for structure ofperipheral nervous systemperipheral nervous system
support cellsupport cell
Common in gangliaCommon in ganglia
May contribute toMay contribute toinsulation of neuroninsulation of neuron
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This type I neuron is ensheathedby processesfrom a satellite glialcell (S), which forms a thinmyelin sheath. On the right is the axon hillock.
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Supporting cellsupporting cells
Neuron
Astrocytes
Oligodendrocytes
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Supporting cellsupporting cells
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Supporting cellsupporting cells
Oligodendrocytes
Astrocytes
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Supporting cellsupporting cells
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Supporting cellsupporting cellsPNS: Glia =Lemmocyte
Nerve fibres
Lemmocyte
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Supporting cellsupporting cells
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Summaryummary
Structuralcharacteristics of a
neuron tell us about
its function
NEURONS
Soma
AxonsDendrites
Synapse
Elaborate
structure of
dendritic tree =
receiver
e.g., Dense Nissl
stain = protein;
suggests
specialization
Structure Correlateswith Function