Cellular NeurobiologyCellular NeurobiologyNeuroscience Research Institute Peking University Department of Neurobiology Peking University Health Science CenterAlbert Cheung-Hoi YU 于常海于常海京大學神經科學研究所京大學神經科學研究所achybjmu.edu.cnOne of the Cajals many drawings of Brain circuity One of the Cajals many drawings of Brain circuityThe letters label the different elements Cajal identified in an area of the human cerebral cortex that controls voluntary movement. Neurons: Excitable cells “wiring”“Signal Senders” Neuroglia: Support, Nurturing, InsulationCellular ComponentsCellular ComponentsNerve CellsNerve CellsNeuronsNeuroglia Cell body (soma; perikaryon) Axon : only one (branches are collaterals; terminals are end feet) Dendrites : much shorter; one or more than one; branch extensively into dendritic treesStructure of NeuronsStructure of NeuronsAxon Hillock(Axonal end feet)The Axon and Axon Collaterals 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: Multiple processes off cell body receive messagesNeurons Structure receive stimuli and transmit afferent impulses to CNS Interneurons communicating between neurons; form circuits in the CNS Motor neuron from CNS to effector cells; deliver efferent impulses out through the PNS to the effectors to carry out the actions directed by the CNSFunctional Classification of NeuronFunctional 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 NeuronsImportant Features of NeuronsAction Potential Action PotentialFour Functional Regions of Model NeuronsFour Functional Regions of Model Neurons Impulse transmission : electrical chemical Morphology : axodendritic axonsomatic axoaxonic dendrodendriticClassification of SynapsesClassification of Synapsessynapse4Vesicles release Neurotransmitters Chemical synapse : presynaptic knob (presynaptic component) synaptic vesicles synaptic cleft postsynaptic membrane (postsynaptic component) Electrical synapse : gap junctionsSynapse StructuresSynapse StructuresTypes of synapseDis- tanceCytoplasmic continuityUltrastruct- ural componentAgent of trans- missionSynaptic delayDirection of trans- missionElectrical3.5 nmYesGap-junction channelIon currentVirtually absentUsually bidirectionalChemical20-40 nmNoPresynaptic vesicle and active zone; postsynaptic receptorsChemical transmittersSignificant: at least 0.3 ms; usually 1-5 ms or longerUni- directionalDistinguishing Properties of Electrical and Chemical Synapses Distinguishing Properties of Electrical and Chemical SynapsesAt a chemical synapse, neurons transmit information across a cleft.1. Small Molecule Neurotransmitter Substances Acetylcholine (ACh); Dopamine (DA); Norepinephrine (NE); Serotonin (5-HT); Histamine 2. Amino Acids Gamma-aminobutyric acid (GABA); Glycine; Glutamate; Aspartate 3.Neuroactive Peptides - partial list! Bradykinin; beta-endorphin; calcitonin; cholecystokinin; enkephalin; dynorphin; insulin; gastrin; substance P; glucagon; secretin; vasopressin; oxytocin, etc. List of Some NeurotransmittersList 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) fast transport system (200 to 400 mm/day)Axonal Transport SystemsAxonal 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 transportAnterograde 200-400Small vesiculotubular structures, neurotransmitters; membrane proteins and lipids Mitochondria50-100MitochondriaRetrograde 200-300Lysosomal vesicles and enzymesSlow transportSCb2-8Microfilaments, metabolic enzymes, clathrin complexSCa0.2-1Neurofilaments and microtubulesMajor Rate Components of Axonal TransportMajor Rate 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 body 2. Neurons communicate with each other through an electrochemical process 3. 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 CellsNeurons differ from Other Cells