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  2. 2. CELLS IN THE NERVOUS SYSTEMGlia Neurons Process informationInsulates, supports, Sense environmental changesand nourishes Communicate changes to other neuronsneurons Command body response
  3. 3. THE NEURON DOCTRINECells are in the range of 0.01 – 0.05 mm of diameterNeed for techniques that allow to see such small structuresHistology Microscopic study of tissue structure The Nissl Stain (late XIX century) Colors selectively only part of the cell (Nissl body) Facilitates the study of cytoarchitecture in the CNS Differentiation between neuron and glia The Golgi Stain (1873) Revealed the entire structure of the neuron
  5. 5. THE NEURON DOCTRINECamillo Golgi’s reticular theoryNeurites of different cells are fused together to form a continuous reticulum, anetwork (like blood circulation)Santiago Ramon y Cajal’s neuron doctrineNeuron are not continuous one another but communicate by contact Shared the 1906 Nobel Prize in Physiology or Medicine
  6. 6. THE NEURONNeuronal membraneseparate the inside from the outsideThe SomaCytosol: Watery fluid inside the cellOrganelles: Membrane-enclosedstructures within the soma Nucleus Rough Endoplasmatic Reticulum, Smooth Endoplasmatic Reticulum, Golgi Apparatus MitochondriaCytoplasm: Contents within a cellmembrane (e.g., organelles, excludingthe nucleus)
  7. 7. THE NUCLEUSContains chromosomes that have thegenetic material (DNA)Genes: segment of DNAGene expression: reading of DNA in orderto synthesize proteinsProtein synthesis happen in the cytoplasmRNA is the messenger that carry theinformation contained in the DNA to thecytoplasm
  8. 8. THE NUCLEUSThe enzyme RNA polymerase binds to the promoter of the gene in order to initiatetranscriptionExons: coding regionsIntrons: non –coding regionsIn the cytoplasm mRNA transcriptis used to assemble proteinsfrom amino acidsDNA transcription mRNA translation Proteins
  9. 9. ROUGH ENDOPLASMATIC RETICULUM Major site for protein synthesis Contains ribosomes attached to the ER and free ribosomesCytosol Membrane
  10. 10. SMOOTH ER and GOLGI APPARATUSSites for preparing/sorting proteins for delivery to different cell regions (trafficking)and regulating substances
  11. 11. THE MITOCHONDRIONSite of cellular respiration (inhale andexhale)Pyruvic acid and O2, trough the Krebscycle are transformed in ATP and CO21 Pyruvic acid = 17 ATPATP- cell’s energy source (by breakdownof ATP in ADP)
  12. 12. THE NEURONAL MEMBRANEBarrier that encloses cytoplasm~5 nm thickProtein concentration in membrane variesStructure of discrete membrane regions influences neuronalfunction
  13. 13. THE CYTOSKELETONNot staticInternal scaffolding of neuronal membraneThree “bones” Microtubules Microfilaments NeurofilamentsMicrotubulesBig and run longitudinally along the neuron.MicrofilamentsSame size of the membrane. Role in changing cellshapeNeurofilamentsMediam size. Structurally very strong
  14. 14. THE AXONThe Axon is specialized for the transferinformation over long distances Axon hillock (beginning) Axon proper (middle) Axon terminal (end)Differences between axon and soma ER does not extend into axon (This means no protein synthesis there) Protein composition: Unique Variable diameter and length
  15. 15. THE SYNAPSEThe axon terminal is the site of contact withanother neuron or cell (synapse) andtransfer of information (synaptictransmission)In the Axon Terminal there are nomicrotubulesPresence of synaptic vesicles (containneurotransmitter)Abundance of membrane proteins postsynapsis)Large number of mitochondria
  16. 16. THE AXOPLASMIC TRANSPORTAllows the transport of the proteinssynthesized in the soma to the axonterminalAnterograde (soma to terminal):could be fast (1000mm per day) orslow (1-10 mm per day). Legs areKinesinRetrograde (terminal to soma)transport: feedback information.Legs are dynein
  17. 17. THE DENDRITE“Antennae” of neuronsAll the dendrites of a neuron are called dendritic treeDendritic spinesPostsynaptic: receives signals from axon terminal by using proteinmolecules called receptors that detect neurotransmitters in the synapticcleft
  18. 18. CLASSIFICATION OF NEURONSClassification Based on the Number of Neurites Single neurite Unipolar Two or more neurites Bipolar- two Multipolar- more than twoClassification Based on Dendritic and Somatic Morphologies Stellate cells (star-shaped) and pyramidal cells (pyramid- shaped) Spiny or aspinous
  19. 19. CLASSIFICATION OF NEURONSFurther Classification By connections within the CNS Primary sensory neurons, motor neurons, interneurons Based on axonal length Golgi Type I - long axon, projection neurons Golgi Type II - short axon, local circuit neurons Based on neurotransmitter type e.g., – Cholinergic = Acetycholine at synapses
  20. 20. GLIAMainly supports neuronal functionsAstrocytes Most numerous glia in the brain Fill spaces between neurons (Influence neurite growth) Regulate the chemical context of the external environment of the neurons Myelinating Glia Oligodendroglia (in CNS) and Schwann cells (in PNS) insulate axons Node of Ranvier: region where the axonal membrane is exposed