1、Cellular NeurobiologyNeuroscience Research InstitutePeking UniversityDepartment of NeurobiologyPeking University Health Science CenterAlbert Cheung-Hoi YU 于常海于常海北京大學神經科學研究所北京大學神經科學研究所One of the Cajals many drawings of Brain circuityThe letters label the different elements Cajal identified in an area
2、 of the human cerebral cortex that controls voluntary movement.Neurons:Excitable cells “wiring”“Signal Senders”Neuroglia:Support,Nurturing,InsulationCellular ComponentsNerve CellsNeuronsNeuroglia Cell body(soma;perikaryon)Axon:only one(branches are collaterals;terminals are end feet)Dendrites:much s
3、horter;one or more than one;branch extensively into dendritic treesStructure of NeuronsAxon Hillock(Axonal end feet)The Axon and Axon Collaterals Cell Body(Soma):Life Support Protein Synthesis Single Nucleus,RER(Nissl Bodies)Axon:Longest process transmits messages away from cell body Dendrites:Multi
4、ple processes off cell body receive messagesNeurons Structure&Function Neurons are similar to other cells in the body in some ways such as:1.Neurons are surrounded by a membrane.2.Neurons have a nucleus that contains genes.3.Neurons contain:What are inside of a neuron?Nucleus NucleolusMicrofilaments
5、/NeurotubulesEndoplasmic Reticulum(ER)Mitochondria Golgi ApparatusNissl BodiesOthers Dendrites:dendrite tree Axon:axon hillock(axon origination)axonal transport system initial segment(first myelin sheath)action potential generation myelin sheath Axon and DendritesAxonsDendritesTake information away
6、from the cell bodyTake information to the cell bodySmooth surfaceRough surface(dendritic spines)Generally only 1 axon per cellUsually many dendrites per cellNo ribosomeHave ribosomesCan have myelinNo myelin insulationBranch further from the cell bodyBranch near the cell bodyDifferences between Axons
7、 and DendritesNeuron Classification by ShapeMultipolar:“multi-”many processesMajority:Single axon,many dendrites(motor neuron and interneuron)Bipolar:“bi-”2 processes Found in some sensory organs(retina,taste,smell,inner ear neuron)Unipolar(pseudo-unipolar):“uni-”1 process(with branches)Sensory affe
8、rent neurons(dorsal root ganglia)Classification of Neurons by MorphologyClassification of Neurons by Axon Length1.Golgi type I NeuronsLong axons(longest from the cortex to the tip of spinal cord,50-70 cm)2.Golgi type II NeuronsShort axons(shortest axons terminate only a few micron from cell body,int
9、erneurons)3.Amacrine NeuronsAn unusual cell type,lack axonsSensory 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
10、 to the effectors to carry out the actions directed by the CNSFunctional Classification of Neuron EXCITABLE Membrane:Able to regulate the movement of ions(charges)across and along membrane SIGNAL TRANSDUCTION DO NOT Replicate:Damaged cells cannot be replaced!Important Features of NeuronsAction Poten
11、tialFour Functional Regions of Model Neurons Impulse transmission:electrical chemical Morphology:axodendritic axonsomatic axoaxonic dendrodendriticClassification of Synapsessynapse4Vesicles release Neurotransmitters Chemical synapse:presynaptic knob(presynaptic component)synaptic vesicles synaptic c
12、left postsynaptic membrane(postsynaptic component)Electrical synapse:gap junctionsSynapse Structures Types of synapseDis-tanceCytoplasmic continuityUltrastruct-ural componentAgent of trans-missionSynaptic delayDirection of trans-missionElectrical3.5 nmYesGap-junction channelIon currentVirtually abse
13、ntUsually bidirectionalChemical20-40 nmNoPresynaptic vesicle and active zone;postsynaptic receptorsChemical transmittersSignificant:at least 0.3 ms;usually 1-5 ms or longerUni-directional Distinguishing Properties of Electrical and Chemical SynapsesAt a chemical synapse,neurons transmit information
14、across a cleft.1.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;enkeph
15、alin;dynorphin;insulin;gastrin;substance P;glucagon;secretin;vasopressin;oxytocin,etc.List of Some Neurotransmitters Axonal transport:intracellular communication Bidirectional mechanism:anterograde transport retrograde transport Classified by transport rates:slow transport system(0.2 to 1 mm/day)fas
16、t transport system(200 to 400 mm/day)Axonal Transport SystemsHitching a Ride on“Retrorail”Membranes of organelles involved in synaptic transmission are returned to the cell body for reuse or degradationNucleusCytoskeleton(Anterograde transport)ComponentRate(mm/day)Structure and compositionFast trans
17、port Anterograde 200-400Small vesiculotubular structures,neurotransmitters;membrane proteins and lipidsMitochondria50-100MitochondriaRetrograde 200-300Lysosomal vesicles and enzymesSlow transport SCb2-8Microfilaments,metabolic enzymes,clathrin complexSCa0.2-1Neurofilaments and microtubulesMajor Rate
18、 Components of Axonal Transport1.Neurons have specialized projections called dendrites and axons.Dendrites take information to the cell body and axons take information away from the cell body2.Neurons communicate with each other through an electrochemical process3.Neurons contain some specialized structures(like synapses)and chemicals(like neurotransmitters)4.Nissl Bodies 5.DO NOT Replicate:Damaged cells cannot be replaced!Neurons differ from Other Cells
