Nervous SystemSlide 2Nervous TissueMajor Structures of the Nervous SystemSubdivisions of the PNSOrganizationSlide 8NeuronsDendritesAxonsStructural Classification of NeuronsSlide 15Slide 16Association or InterneuronsNeuroglial CellsNeuroglial Cells (CNS): AstrocytesNeuroglial Cells (CNS): OligodendrocytesNeuroglial Cells (CNS): MicrogliaNeuroglial Cells (CNS): Ependymal cellsNeuroglial Cells (PNS): Satellite CellsNeuroglial Cells (PNS): Schwann CellMyelinationMyelination: PNSSlide 27Myelination: CNSGray and White MatterSlide 30Electrical Signals in NeuronsIon ChannelsGated Ion Channels (Voltage-Gated)Gated Ion Channels (Ligand-Gated)Action PotentialRepolarizing Phase of Action PotentialRefractory Period of Action PotentialPropagation of Action PotentialContinuous versus Saltatory ConductionSaltatory ConductionSlide 52Signal Transmission at SynapsesChemical SynapsesExcitatory & Inhibitory PotentialsSlide 56Removal of NeurotransmitterSummationSlide 59Summation: Three Possible ResponsesSlide 64Neurotransmitter EffectsSmall-Molecule NeurotransmittersSlide 68Small-Molecule Neurotransmitters (2)Small-Molecule Neurotransmitters (3)NeuropeptidesSlide 72Neuronal CircuitsSlide 74Slide 75Slide 76Slide 771Nervous SystemI. OverviewII. HistologyIII. Electrical SignalsIV. Signal Transmission at SynapsesV. NeurotransmittersVI. Neural CircuitsVII. RepairsVIII.Pathology2Nervous SystemI. Overview1. Structures2. Functions3. OrganizationII. HistologyIII. Electrical SignalsIV. Signal Transmission at SynapsesV. NeurotransmittersVI. Neural CircuitsVII. RepairsVIII. Pathology3Nervous TissueControls and integrates all body activities within limits that maintain lifeThree basic functions1. sensing changes with sensory receptors2. interpreting and remembering those changes3. reacting to those changes with effectors4Major Structures of the Nervous SystemBrainspinal cordcranial nervesspinal nervesganglia enteric plexuses sensory receptors6Subdivisions of the PNS1. Central nervous system (CNS) 2. Peripheral nervous system (PNS)a) Somatic (voluntary) nervous system (SNS)b) Autonomic (involuntary) nervous systems (ANS)c) Enteric nervous system (ENS)7OrganizationIntegration MotorSensorySNS(Sensory)ANS(Sensory)BrainSpinal cordSNS(Motor)ANS(Motor)ENS(Sensory)8Nervous SystemI. OverviewII. Histology1. Neurons2. Neurogliaa) CNSb) PNS3. Myelination4. Gray and White MatterIII. Electrical SignalsIV. Signal Transmission at SynapsesV. NeurotransmittersVI. Neural CircuitsVII. RepairsVIII. Pathology9NeuronsFunctional unit of nervous system1. Cell bodya) Nissl bodies b) Neurofilaments c) Microtubules d) Lipofuscin pigment clumps2. Cell processes a) Dendrites b) Axons11DendritesConducts impulses towards the cell bodyTypically short, highly branched & unmyelinatedSurfaces specialized for contact with other neuronsContains neurofibrils & Nissl bodiesimpulse12AxonsConduct impulses away from cell bodyLong, thin cylindrical process of cell Arises at axon hillock Impulses arise from initial segment (trigger zone)Side branches (collaterals) end in fine processes called axon terminalsSwollen tips called synaptic end bulbs contain vesicles filled with neurotransmitters14Structural Classification of NeuronsBased on number of processes found on cell body1. multipolar = several dendrites & one axonmost common cell type2. bipolar neurons = one main dendrite & one axonfound in retina, inner ear & olfactory 3. unipolar neurons = one process only(develops from a bipolar)are always sensory neurons15Structural Classification of NeuronsBased on number of processes found on cell body1. multipolar = several dendrites & one axonmost common cell type2. bipolar neurons = one main dendrite & one axonfound in retina, inner ear & olfactory 3. unipolar neurons = one process only(develops from a bipolar)are always sensory neurons16Structural Classification of NeuronsBased on number of processes found on cell body1. multipolar = several dendrites & one axonmost common cell type2. bipolar neurons = one main dendrite & one axonfound in retina, inner ear & olfactory 3. unipolar neurons = one process only(develops from a bipolar)are always sensory neurons17Association or InterneuronsNamed for histologist that first described them or their appearance18Neuroglial CellsHalf of the volume of the CNS Smaller cells than neurons50X more numerousCells can divide rapid mitosis in tumor formation (gliomas)4 cell types in CNSastrocytes, oligodendrocytes, microglia & ependymal2 cell types in PNSschwann and satellite cells19Neuroglial Cells (CNS): AstrocytesStar-shaped cellsForm blood-brain barrier by covering blood capillariesMetabolize neurotransmittersRegulate K+ balanceProvide structural support20Neuroglial Cells (CNS): OligodendrocytesMost common glial cell typeEach forms myelin sheath around more than one axons in CNSAnalogous to Schwann cells of PNS21Neuroglial Cells (CNS): MicrogliaSmall cells found near blood vesselsPhagocytic role -- clear away dead cellsDerived from cells that also gave rise to macrophages & monocytes22Neuroglial Cells (CNS): Ependymal cellsForm epithelial membrane lining cerebral cavities & central canalProduce cerebrospinal fluid (CSF)23Neuroglial Cells (PNS): Satellite CellsFlat cells surrounding neuronal cell bodies in peripheral gangliaSupport neurons in the PNS ganglia24Neuroglial Cells (PNS): Schwann CellCells encircling PNS axonsEach cell produces part of the myelin sheath surrounding an axon in the PNS25MyelinationInsulation of axonIncrease speed of nerve impulse26Myelination: PNSAll axons surrounded by a lipid & protein covering (myelin sheath) produced by Schwann cellsNeurilemma is cytoplasm & nucleusof Schwann cellgaps called nodes of RanvierMyelinated fibers Unmyelinated fibersNode of Ranvier27Myelination: PNSSchwann cells myelinate (wrap around) axons in the PNS during fetal developmentSchwann cell cytoplasm & nucleus forms outermost layer of neurolemma with inner portion being the myelin sheathTube guides growing axons that are repairing themselves28Myelination: CNSOligodendrocytes myelinate axons in the CNS Broad, flat cell processes wrap about CNS axons, but the cell bodies do not surround the axonsNo neurilemma is formedLittle regrowth after injury is possible due to the lack of a distinct tube or