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lec 2 Neurons_Neuroanatomy2014 - Nervous System Structure...

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1Nervous System Structure andCellular ComponentsBio 334Gross Organization of the Cerebral Cortex
2Functional Organization of the Cerebral CortexFunctional Organization of the Cerebral Cortex
3Cell Types of the BrainThe brain is made of two types of cells:neuronsandglia.Neurons~100 billion neurons in the human brainNeurons carry out most (all?) of the information processing in thenervous systemEnormous diversity of structure and function, as we will seeshortlyGliaOutnumber neurons by 10 to 1Main roles are in maintaining homeostasis of extracellular spacein the brain, insulating neurons, and providing both structural andnutrient support to neuronsTypically divided into only three types (although this probablyreflects our relative ignorance of glial cell function): astrocytes,oligodendrocytes, and microgliaThe “Neuron Doctrine” is a recent conceptPrior to the late 1800’s it was thought that nerves andthe brain consisted of a continuous network of fusedcells. One variant of this was “hydraulic” models ofneural function, before it became clear that the nervoussystem operates using electrical signals.The most noted proponent of the idea that neurons areseparate cells (the “neuron doctrine”) that mustcommunicate in some way at contact points wasSantiago Ramon y Cajal.Cajal used the Golgi stain (invented byCamillo Golgiin1873) to study neuroanatomy, and he concluded thatnerve cells are in fact not continuous with each other.Golgi vigorously disputed the neuron doctrine, althoughGolgi and Cajal shared the Nobel Prize in 1906. Cajal, ofcourse, was right.
4Golgi and Cajal: Pioneers of Neuronal StructureA Golgi-stained neuronin the cerebral cortexSantiago Ramon y CajalCamillo GolgiThe Basic Parts of a NeuronCell body, where the nucleus is locatedsynonyms: soma (plural: somata),perikaryon (plural: perikarya)Neurites: thin processes that radiate outfrom the somaTwo types of neurites: dendrites, axonGenerally speaking, dendrites receiveincoming signals from other neurons,and axons carry output signals toother neurons (although there areexceptions to both rules)Also generally speaking, a neuron cellbody gives rise to only a single axon(which might subsequently branchprofusely) but many dendrites
5Neurons come in many shapes and sizesPurkinje cell from cerebellumJust a few examples:The plasma membrane is theexternal membrane that separatesthe intracellular space from theextracellular space.As we will see in subsequentlectures, the characteristics of theneuronal plasma membrane arecrucial for the generation andtransmission of electrical signals inthe brain.The cell body contains an aqueouscytosol (a potassium-rich saltsolution) and membrane-boundorganelles:• nucleus• rough endoplasmic reticulum• smooth endoplasmic reticulum• Golgi apparatus• mitochondria.

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Term
Fall
Professor
Matthews

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