[神经生物学_课件_北大]_2_1神经元和神经胶质细胞-神经元.doc

Cellular NeurobiologyAlbert Cheung-Hoi YU 于常海 京大學神經科學研究所Neuroscience Research Institute Peking UniversityDepartment of Neurobiology Peking University Health Science COne of the Cajals many drawings ofBrain circuityThe letters label the differentelements Cajal identified in anarea of the human cerebralcortex that controls voluntarymovement.Cellular Components Neurons: Excitable cells “wiring” “Signal Senders” Neuroglia: Support, Nurturing,InsulationNerve CellsNeurons NeurogliaStructure of Neurons Cell body (soma; perikaryon) Axon : only one (branches are collaterals;terminals are end feet) Dendrites : much shorter; one or more thanone; branch extensively into dendritic trees (Axonal end feet)Axon HillockThe Axonand AxonCollateralsNeurons Structure & Function Cell Body (Soma): Life Support Protein Synthesis Single Nucleus, RER (Nissl Bodies) Axon: Longest process transmits messagesaway from cell body Dendrites: Multiple processes off cellbody receive messagesWhat are inside of a neuron? Neurons are similar to other cells in thebody in some ways such as:1. Neurons are surrounded by a membrane.2. Neurons have a nucleus that contains genes.3. Neurons contain :NucleusNucleolusMicrofilaments/Neuro tubulesEndoplasmic Reticulum (ER) MitochondriaGolgi ApparatusNissl BodiesOthersAxon and Dendrites Dendrites : dendrite tree Axon : axon hillock (axon origination) axonal transport system initial segment (first myelin sheath) action potential generation myelin sheathDifferences between Axons and DendritesAxons DendritesTake information away Take information to the cellfrom the cell body bodySmooth surface Rough surface (dendritic spines)Generally only 1 axon percellUsually many dendrites percellNo ribosome Have ribosomesCan have myelin No myelin insulationBranch further from thecell bodyBranch near the cell bodyNeuron Classification by ShapeMultipolar: “multi-” many processesMajority: Single axon, many dendrites (motorneuron and interneuron)Bipolar: “bi-” 2 processesFound in some sensory organs (retina, taste,smell, inner ear neuron)Unipolar (pseudo-unipolar): “uni -” 1 process (withbranches)Sensory afferent neurons (dorsal root ganglia)Classification of Neurons byMorphologyClassification of Neuronsby Axon Length1. Golgi type I Neurons Long axons (longest from the cortex to the tip of spinal cord, 50-70 cm)2. Golgi type II Neurons Short axons (shortest axons terminate only a few micron from cell body, interneurons)3. Amacrine Neurons An unusual cell type, lack axonsFunctional Classification of NeuronSensory neuron from receptor to CNS; receive stimuli and transmit afferent impulses to CNSInterneurons communicating between neurons; form circuits in the CNSMotor neuron from CNS to effector cells; deliver efferent impulses out through the PNS to the effectors to carry out the actions directed by the CNSImportant Features of Neurons EXCITABLE Membrane: Able to regulate the movement of ions (charges) across and along membrane SIGNAL TRANSDUCTION DO NOT Replicate: Damagedcells cannot be replaced!ActionPotentialFour Functional Regions of Model NeuronsClassification of Synapses Impulse transmission : electrical chemical Morphology : axodendritic axonsomatic axoaxonic dendrodendriticVesicles release Neurotransmitters4synapseSynapse Structures Chemical synapse : presynaptic knob (presynaptic component) synaptic vesicles synaptic cleft postsynaptic membrane (postsynapticcomponent) Electrical synapse : gap junctionsDistinguishing Properties ofElectrical and Chemical SynapsesTypes ofsynapseDis-tanceCytoplasmic continuityUltrastruct- uralcomponentAgent of trans-missionSynaptic delayDirection of trans- missionElectrical 3.5 nm Yes Gap-junction channelIon current Virtually absentUsuallybidirectionalChemical 20-40 nm No Presynaptic vesicle and active zone;postsynaptic receptorsChemicaltransmitters Significant: at least 0.3 ms;usually 1-5 ms or longerUni-directionalAt a chemical synapse, neurons transmit information across a cleft.List of Some Neurotransmitters1. Small Molecule Neurotransmitter SubstancesAcetylcholine (ACh); Dopamine (DA); Norepinephrine(NE); Serotonin (5-HT); Histamine2. Amino AcidsGamma-aminobutyric acid (GABA); Glycine; Glutamate;Aspartate3.Neuroactive Peptides - partial list!Bradykinin; beta-endorphin; calcitonin; cholecystokinin;enkephalin; dynorphin; insulin; gastrin; substance P;glucagon; secretin; vasopressin; oxytocin, etc.Axonal Transport Systems Axonal transport : intracellular communication Bidirectional mechanism : anterograde transport retrograde transport Classified by transport rates : slow transport system (0.2 to 1 mm/day) fast transport system (200 to 400 mm/day)Hitching aRide on“Retrorail”NucleusMembranes of organellesinvolved insynaptictransmission arereturned to theCytoskeletoncell body for(Anterograde transport)reuse or degradationMajor Rate Components of Axonal TransportComponent Rate Structure and composition(mm/day) Fast transportAnterograde 200-400 Small vesiculotubular structures,neurotransmitters; membrane proteins and lipidsMitochondria 50-100 MitochondriaRetrograde 200-300 Lysosomal vesicles and enzymesSlow transportSCb 2-8 Microfilaments, metabolic enzymes,clathrin complexSCa 0.2-1 Neurofilaments and microtubulesNeurons differ from Other Cells1. Neurons have specialized projections called dendrites and axons. Dendrites takeinformation to the cell body and axon