Nerve Tissue - Nikolai Lazarov's web-sitenikolai.lazarov.pro/.../2014/medicine/histology/06_Nerve_Tissue.pdf · Nerve tissue 1.Nerve tissue –characteristic s, histogenesis and classification

Nerve tissueNerve tissue1.1.Nerve tissueNerve tissue –– characteristiccharacteristicss, , histogenesishistogenesis and classificationand classification

2.2.NeuronsNeurons –– classesclasses and structureand structure::

�� cell body (perikaryon)cell body (perikaryon)

�� neuronal processesneuronal processes

3.3.Nerve fibersNerve fibers –– typestypes

4.4.SynapsesSynapses

5.5.Neurotransmitters and receptorsNeurotransmitters and receptors

6.6.Neuroglial cellsNeuroglial cells

7.7.Nerve endingsNerve endings::

�� sensorysensory ((afferentafferent)) receptorsreceptors

�� effector (efferent) endingseffector (efferent) endings

Prof. Dr. Nikolai LazarovProf. Dr. Nikolai Lazarov 22

Nerve tissueNerve tissue

� main functions: � sensing stimuli and

creating, analyzing and integrating information

� regulates and controls body functions

� provides the unity with the environment

� properties:�� iirritabilityrritability

� capacity to respond to a stimulusto respond to a stimulus –

generation of a nerve impulsegeneration of a nerve impulse

�� conductivityconductivity

�� capacity to transfer the responsecapacity to transfer the responsethroughout the neuron by the plasma membrane

� Textus nervosus:Textus nervosus:�� cellscells –– nervenerve and glial cellsand glial cells�� extracellular matrixextracellular matrix


Classification of nervous systemClassification of nervous system


NeurulationNeurulation

� embryonic origin:

�� neuroectodermneuroectoderm

� formation of neural tube (neurulationneurulation)

� begin of the process – E17

� neural (primary embryonic) induction –signaling molecules (growth factors) fromthe underlying notochord:

�� neural plateneural plate

�� neural grooveneural groove

�� neural foldneural fold

�� neural tube neural tube � CNSCNS

�� neural crestneural crest �� ganglion ridgeganglion ridge � PNSPNS

� transverse segmentation of neural tube:

� cranial neuropore – Е25

� caudal neuropore – Е27


HistogenesisHistogenesis

�� undifferentiated neuroepithelial cells undifferentiated neuroepithelial cells (stem cells) (stem cells) –– pluripotential:pluripotential:

�� histogenesishistogenesis –– zones::�� ependymal layerependymal layer

�� mantle layermantle layer

�� marginal layermarginal layer

�� unipotentunipotent progenitor cellsprogenitor cells::�� neuroblastsneuroblasts (immature neurons)

� unipolar, bipolar and multipolar

�� glioblastsglioblasts (glial precursor cells)� oligodendrocytes� protoplasmic astrocytes� fibrillar astrocytes

�� ependymal cellsependymal cells

�� microgliamicroglia � mesenchymal origin?


� neuron – more than 10 billion in the human NS�� cell body (perikaryoncell body (perikaryon)�� axonaxon – Golgi type І and ІІ neurons

�� dendritesdendrites

Nerve cellsNerve cells


�� perikaryonperikaryon (Gr. periperi, around + karyon,karyon, nucleus)� a trophic and receptive center of the neuron� diameter – 20-40 µm (4-120 µm)� shape – pyramidal, stellate, fusiform, flask-shaped etc.

Cell bodyCell body

� composition:� large, euchromatic nucleus with

a prominent nucleolus� organelles:

� Nissl bodies� Golgi complex� mitochondria� microtubules� neurofilaments� lypofuscin and

neuromelanin


�� axonaxon (Lat. axis,axis, axle or pivot)� length – 1 mm-100 cm� diameter – 0.2-20 µm

Nerve processesNerve processes

� structure:�� axon hillockaxon hillock�� initial segmentinitial segment�� collateralcollateral branches�� axonalaxonal ending (terminal)terminal)

� synapse�� axolemmaaxolemma�� axoplasmaxoplasm:

� ribosomes – occasionallyabsence of rER and GA

�� axonal transportaxonal transport:�� slowslow streamstream – 0.2 µm/day

anterograde flow

�� fastfast streamstream – 10-40 cm/dayanterograde and retrograde flow


�� dendritesdendrites (Gr. dendron,dendron, tree)� number – variable, most frequently 5-15� 80-90% of the surface

Nerve processesNerve processes

� structure:� short, dendritic treedendritic tree�� dendritedendrite spinesspines� dendritic cytoplasmcytoplasm:

� Nissl bodies� mitochondria� neurofilaments� microtubules� absence of Golgi complex


Basic neuronal typesBasic neuronal types

� morphological classes:�� pseudounipolar neuronspseudounipolar neurons

�� bipolar neuronsbipolar neurons

�� multipolar neuronsmultipolar neurons

� functional classes:�� motormotor ((efferentefferent)) neuronsneurons

�� sensorysensory ((afferentafferent)) neuronsneurons

�� interneuronsinterneurons


�� Nerve fiberNerve fiber::� axon� sheath derived from cells of ectodermal origin:

� oligodendrocyte – CNS� Schwann cell – PNS

Nerve fibersNerve fibers

� Types of nerve fibersnerve fibers:�� unmyelinatedunmyelinated – 0.1-2 µm diameter

� both in the CNS and PNS� absence of nodes of Ranvier� 0.5-2 m/sec conduction velocity

�� myelinatedmyelinated – 1-20 µm� both in the CNS and PNS�� mesaxonmesaxon�� nodes ofnodes of RanvierRanvier�� internodalinternodal segmentsegment – 1-2 mm

�� SchmidtSchmidt--LantermanLanterman cleftsclefts� 4-120 m/sec velocity


�� myelinationmyelination in humansin humans::� begin – fetal period� end – 7 years� regulation – neuroregulin NRG1

MyelinationMyelination

� Myelin-forming cells:�� oligodendrocytesoligodendrocytes – CNS�� Schwann cellsSchwann cells – PNS

�� myelinmyelin::� lipids – 70%� proteins – 30% in CNS

� MBP (myelin basic protein)� P0 – peripheral axons� PMP-22 – peripheral axons

� myelin sheath:� major dense lines� intraperiod lines


� structure:�� presynaptic componentpresynaptic component,,

axon terminal� presynaptic membrane� presynaptic grid�mitochondria� synaptic vesicles –

(20-65 nm) � transmitters

� synaptic cleft (20-30 nm)

� postsynaptic membrane� postsynaptic thickening� receptors

C.S. SherringtonC.S. Sherrington18571857––19521952

SynapsesSynapses

�� synapsesynapse (Gr. ssynapteinynaptein,, to join together)


� way of transmission:�� electrical synapseselectrical synapses�� chemical synapseschemical synapses

Types of synapsesTypes of synapses

� contacting structures:� axosomatic synapses� axodendritic� axoaxonic� dendrodendritic� somatodendritic etc.

� morphologically:� asymmetrical (type I) – Glu� symmetrical (type IІ) – GABA

�� functionallyfunctionally::� excitatory synapses� inhibitory synapses

� atypical synapses:� reciprocal dendrodendritic

�serial synapses�“ribbon” synapse�synaptic glomeruli


NeurotransmittersNeurotransmitters

� types of neurotransmitters:� classical transmitters

� amino acids� biogenic amines� other major transmitters – ACh

� neuroactive peptides (neuropeptides)

�� atypical neuralatypical neural messengers:� arachidonic acid derivatives � purines

� adenosine, ATP� gaseous – NO, CO

� postsynaptic effect:� excitatory

� acetylcholine� glutamate� aspartate

� inhibitory�monoamines�GABA and glycine

�� neurotransmittersneurotransmitters – criteria

�� neuromodulatorsneuromodulators


�� TransportersTransporters:�� integral proteinsintegral proteins ––

NaNa++ transporttransport symporterssymporters

Transporters and receptorsTransporters and receptors

� Transmitter receptorsreceptors:�� ionotropicionotropic –– transmittertransmitter--gatedgated ionion channelschannels

� for ACh, GABA, Gly, SER� for glutamate

• NMDA-receptors• non-NMDA-receptors (AMPA and kainate)

�� metabotropic receptorsmetabotropic receptors�� GG--proteinprotein--coupled receptorscoupled receptors

• muscarinic ACh receptors• α- and β-adrenergic receptors• receptors for Glu, SER, GABA, neuropeptides

�� tyrosine kinasestyrosine kinases rreceptor eceptor familyfamily�� guanylate cyclguanylate cyclase ase rreceptoreceptorss�� cytokine receptorscytokine receptors

�� autoreceptorsautoreceptors

�� AcetylcholinesteraseAcetylcholinesterase (AChE)


Arvid CarlssonArvid CarlssonArvid CarlssonArvid Carlsson, Paul GreengardPaul GreengardPaul GreengardPaul Greengard andandandand Eric Kandel Eric Kandel Eric Kandel Eric Kandel for their discoveries for their discoveries for their discoveries for their discoveries concerning "signal transduction in the nervous system"concerning "signal transduction in the nervous system"concerning "signal transduction in the nervous system"concerning "signal transduction in the nervous system"

Arvid CarlssonArvid CarlssonArvid CarlssonArvid Carlsson, Department of Pharmacology, Göteborg University, Sweden,

is rewarded for his discovery that dopamine is a brain transmitter of great

importance for our ability to control movements that has led to the realization

that Parkinson's disease is caused by a lack of dopamine in certain parts of the

brain.

Paul GreengardPaul GreengardPaul GreengardPaul Greengard, Laboratory of Molecular and Cellular

Science, Rockefeller University, New York, USA, is

rewarded for his discovery of how dopamine and a

number of other transmitters exert their action in the

nervous system.

Eric KandelEric KandelEric KandelEric Kandel, Center for Neurobiology and Behavior, Columbia

University, New York, USA, is rewarded for his discoveries of how

the efficiency of synapses can be modified, and which molecular

mechanisms that take part.


NeurogliaNeuroglia

�� centralcentral gliocytesgliocytes

– neural tube:

�� astrocytesastrocytes

�� oligodendrocytesoligodendrocytes

�� ependymal cellsependymal cells

��microglial cellsmicroglial cells

�� peripheral gliocytesperipheral gliocytes – neural crest:

��SchwannSchwann cellscells ((neurolemmocytesneurolemmocytes))

�� satellite cells ofsatellite cells of CajalCajal

((syn: mantle cells or amphicytessyn: mantle cells or amphicytes))

� Glial cells – glioblastic origin:�� centralcentral –– macrogliamacroglia and microgliaand microglia ((inin CNSCNS))�� peripheralperipheral –– in PNSin PNS


Central gliocytesCentral gliocytes

�� oligodendrocytesoligodendrocytes� large light

� medium-sized

� small dark – ¼ of the light cells

� myelin-forming cells in the CNS

�� ependymal cellsependymal cells – neural crest

� line the ventricles of the brain and central canal of the spinal cord

� absorption and secretion of cerebrospinal fluid (liquor)

� tanycytes (ependymal astrocytes)

�� microgliamicroglia –– 15%15% ofof thethe totaltotal cellscells of CNS

� non-dividing cells

� derived from monocytes

� role of macrophages (mononuclear phagocyte system in nervous tissue)

�� astrocytesastrocytes�� protoplasmicprotoplasmic�� fibrous astrocytesfibrous astrocytes

((GrGr. . astronastron–– starstar))

((Gr. Gr. oligosoligos–– smallsmall))


Peripheral gliocytesPeripheral gliocytes

� neural crest origin

� myelin-forming cells in the PNS

� maintenance of the axon integrity

� phagocytotic activity and cellular debris that allows for regrowth of PNS neuron

�� SchwannSchwann cellscells ((neurolemmocytesneurolemmocytes))

�� satellite cellssatellite cells ((amphicytesamphicytes))� in sensory and autonomic ganglia

�help regulate the external chemical environment


�� 3 main groups 3 main groups –– SherringtonSherrington, 1906, 1906::

�� exteroceptorsexteroceptors

�� proprioceptorsproprioceptors

�� interoceptorsinteroceptors

�� by sensory modality:by sensory modality:

�� baroreceptorsbaroreceptors – respond to pressure

�� chemoreceptorschemoreceptors – chemical stimuli

�� mechanoreceptorsmechanoreceptors – mechanical stress

�� nociceptorsnociceptors – pain perception

�� thermoreceptorsthermoreceptors – temperature

(heat, cold or both)

�� by location:by location:

�� cutaneous receptorscutaneous receptors – in the skin

�� muscle spindlesmuscle spindles – in the muscles

�� by morphologyby morphology:

�� free nerve endingsfree nerve endings

�� encapsulated receptorsencapsulated receptors

C.S. SherringtonC.S. Sherrington18571857––19521952

Sensory receptorsSensory receptors –– classificationclassification


�� free nerve endingsfree nerve endings:

� unencapsulated

� unspecialized, detect pain

� most widely distributed, most numerous in the skin, mucous&serous membranes, muscle, deep fascia, viscera walls

�� peritrichal endings of hair folliclesperitrichal endings of hair follicles

�� tactile discs of tactile discs of MerkelMerkel:�mechanoreceptors –

pressure and texture

�superficial layers of glabrous and hairy skin

Sense of touchSense of touch

�� four kinds of touch sensationsfour kinds of touch sensations::�� light tlight touchouch (contact)(contact)

�� coldcold

�� heatheat

�� painpain


�� tactile corpuscles of tactile corpuscles of MeissnerMeissner – glabrous skin

�� end bulbs (of end bulbs (of KrauseKrause)) – responds to pressure,

genital corpusclesgenital corpuscles

Encapsulated receptorsEncapsulated receptors

�� Pacinian (Pacinian (VaterVater--PaciniPacini) corpuscles) corpuscles – vibration

�� GolgiGolgi--Mazzoni Mazzoni corpusclescorpuscles – in the fingertips

�� RuffiniRuffini endingsendings – responds to pressure

�� neurotendinous organs (neurotendinous organs (GolgiGolgi tendon organs)tendon organs)

�� neuromuscular spindles neuromuscular spindles – proprioceptors::

�� intrafusal fibersintrafusal fibers

�� extrafusal fibersextrafusal fibers


�� structurestructure::

�� myelinated axonmyelinated axon �� collateralscollaterals

�� ~~50 50 axon terminals (boutons)axon terminals (boutons)

•• synaptic vesiclessynaptic vesicles –– ACh ACh

•• presynaptic membranepresynaptic membrane

�� sarcolemmasarcolemma �� junctional folds junctional folds

postsynaptic membranepostsynaptic membrane

• nicotinic ACh ACh receptors

�� autonomic effector endings:autonomic effector endings:

�� sympatheticsympathetic –– adrenergicadrenergic ((NANA))

�� parasympatheticparasympathetic –– cholinergiccholinergic ((AChACh))

�� purinergicpurinergic –– ATPATP and adenosineand adenosine

�� do not makedo not make

specialized synaptic contactssynaptic contacts

Effector nerve endingsEffector nerve endings

�� myoneural junction myoneural junction –– motor end platemotor end plate::


Thank youThank youThank youThank youThank youThank youThank youThank you……………………

Nerve Tissue - Nikolai Lazarov's web-sitenikolai.lazarov.pro/.../2014/medicine/histology/06_Nerve_Tissue.pdf · Nerve tissue 1.Nerve tissue –characteristic s, histogenesis and classification

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