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1、Cellular Neurobiology,Neuroscience Research InstitutePeking UniversityDepartment of NeurobiologyPeking University Health Science Center,Albert Cheung-Hoi YU 于常海,北京大學(xué)神經(jīng)科學(xué)研究所,One of the Cajals many drawings of Brain circuity,The letters label the different elements Cajal identified in an area of the h

2、uman cerebral cortex that controls voluntary movement.,Neurons: Excitable cells “wiring” “Signal Senders”Neuroglia: Support, Nurturing, Insulation,Cellular Components,Nerve Cells,Neurons,Neuroglia,Cell body (soma; perikaryon) Axon : only one (branches are collaterals; terminals are end feet)Dendrite

3、s : much shorter; one or more than one; branch extensively into dendritic trees,Structure of Neurons,Axon Hillock,(Axonal end feet),The Axon and Axon Collaterals,Cell Body (Soma): Life SupportProtein SynthesisSingle Nucleus, RER (Nissl Bodies)Axon: Longest process transmits messages away from cell b

4、odyDendrites: Multiple processes off cell body receive messages,Neurons 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?,N

5、ucleus NucleolusMicrofilaments/Neurotubules,Endoplasmic Reticulum (ER) Mitochondria Golgi ApparatusNissl BodiesOthers,Dendrites :dendrite treeAxon :axon hillock (axon origination)axonal transport systeminitial segment (first myelin sheath)action potential generationmyelin sheath,Axon and Dendrites,D

6、ifferences between Axons and Dendrites,Neuron Classification by Shape,Multipolar: “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): “u

7、ni -” 1 process (with branches)Sensory afferent neurons (dorsal root ganglia),Classification of Neurons by Morphology,Classification of Neurons by Axon Length,Golgi type I NeuronsLong axons (longest from the cortex to the tip of spinal cord, 50-70 cm)Golgi type II NeuronsShort axons (shortest axons

8、terminate only a few micron from cell body, interneurons)Amacrine NeuronsAn unusual cell type, lack axons,Sensory 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 ce

9、lls; deliver efferent impulses out through the PNS to the effectors to carry out the actions directed by the CNS,Functional Classification of Neuron,EXCITABLE Membrane: Able to regulate the movement of ions (charges) across and along membrane SIGNAL TRANSDUCTIONDO NOT Replicate: Damaged cells cannot

10、 be replaced!,Important Features of Neurons,Action Potential,Four Functional Regions of Model Neurons,Impulse transmission : electrical chemical Morphology : axodendriticaxonsomaticaxoaxonicdendrodendritic,Classification of Synapses,synapse,4,Vesicles release Neurotransmitters,Chemical synapse :pres

11、ynaptic knob (presynaptic component)synaptic vesiclessynaptic cleftpostsynaptic membrane (postsynaptic component)Electrical synapse :gap junctions,Synapse Structures,Distinguishing Properties of Electrical and Chemical Synapses,At a chemical synapse, neurons transmit information across a cleft.,Smal

12、l Molecule Neurotransmitter SubstancesAcetylcholine (ACh); Dopamine (DA); Norepinephrine (NE); Serotonin (5-HT); Histamine Amino AcidsGamma-aminobutyric acid (GABA); Glycine; Glutamate; AspartateNeuroactive Peptides - partial list!Bradykinin; beta-endorphin; calcitonin; cholecystokinin; enkephalin;

13、dynorphin; insulin; gastrin; substance P; glucagon; secretin; vasopressin; oxytocin, etc.,List of Some Neurotransmitters,Axonal transport : intracellular communicationBidirectional mechanism :anterograde transport retrograde transport Classified by transport rates :slow transport system (0.2 to 1 mm

14、/day) fast transport system (200 to 400 mm/day),Axonal Transport Systems,Hitching a Ride on “Retrorail”,Membranes of organelles involved in synaptic transmission are returned to the cell body for reuse or degradation,Nucleus,Cytoskeleton,(Anterograde transport),Major Rate Components of Axonal Transp

15、ort,1. 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

16、) and chemicals (like neurotransmitters)4. Nissl Bodies 5. DO NOT Replicate: Damaged cells cannot be replaced!,Neurons differ from Other Cells,Neuron :Supporting cells :CNS : neuroglia (glia)PNS : Schwann cells and satellite cellsFunctions :physical supportelectrical insulationmetabolic exchangeblood-brain barrier,Composition of Nervous Tissue,Neuroglia in the CNS,Able to replicate!Importance in nervous system function is VASTLY underestimated!Evidence is mounting: Nurturing roleSignaling role (