·334·PARTVINERVOUSSYSTEMPes hippocampiInferior hom of lateral ventricleUncusHippocampusPahippocampal gyrusDentate gyrusFimbriaCollateraleminenceSplenium-CollateraltrigoneForceps majBulb of posterior comiCalcar aviPosteriorcormuA.hippocampus,the posterior inferior horn of the rightlateral ventricle(posted from above)HippocampusFimbriaAlveusFimbriodentatesulcusPolymorphic layer-Pyramidal layerDentategyrus-Molecular layerProsubiculumInferior horn of lateral ventricleSubiculum-Presubiculum/ParasubiculumEntorhinal areaB.hippocmpus andrelated struture(seen in a coronal sectionofthefloorofthe inferiorhomofthelateral ventricle)Fig.VI-2-39 Hippocampus and hippocampal formationIn the limbic system,hippocapal efferent fibersThe limbic system participates in the organizationtravel in the fomix and synapse neurons in the ma-of the autonomic nervous system. Most of the limbicmillary bodies.These neurons of the mamillary bodysystem output connects to hypothalamus, in part viaproject axons to the anterior thalamic nuclei via thethe medial forebrain bundle. Stimulation of variousmamillothalamic tract.The anterior thalamic nucleilimbic system can produces changes in cardiovascularproject, in turn, to the cingulate gyrus, which containsor gastrointestinal functions. However, the sympathet-the cingulum that reaches the parahippocampal gyrus.ic and parasympathetic aspects of autonomic controlSo, the circuit is formed: parahippocampal gyrusare not well localized in the limbic system.hippocampal formation -mamillary bodies-→anteri-The limbic system, especially the hippocampusor thalamic nuclei -cingulate gyrusparahippocam-together with the mamillary body and the portionspal gyrus. This circuit ties together the cerebral cortexof the cerebrum, functions in memory and learningand hypothalamus, called the hippocampal circuit orExperimental and clinical observations suggest thatPapez circuit after the neuroanatomist who defined it.memory impairment results from lesions in the limbicIt provides an anatomic substrate for the convergencesystem. People with the hippocampus and adjacentofcognitive (cortical learning and memory)activities,cortex in the medial temporal lobes damage may for-emotional experience, and expression.get recent events and even cannot commit anything to扫描全能王创建
Chapter 2 Central Nervous System · 335 .tiaa40% of the weight of the human brain. Phylogenet-atailyutwmically,the cerebral cortex is often divided into twotemfunctionsinmemoryremains uncleartypes: an older (original) part, consisting of the ar-Thelimbicsystemalsofunctionsinthemotionalchicortex (including hippocampus and dentate gyrus)aspcsobhavilatdsurivalEermenand paleocortex (mesocortex), such as entorhinalonthelimbicsystemofmonkeysandotheranimalscortex,and a newer development,neocortex.Thecorindicatethatheamygdaloidnucleusassumesamajortex has a characteristic structure, consisting of nerveroleincontrolling theoverall patternofbehaviorcells (neurons) and nerve fibers arranged in layers.Amygdaloid body reives thefibers from hypothal.Generally,the ncocertex can be divided into six layersamusandassociationareasinthfronta,temporal(Fig.VI-2-40),from the most external surface to theinulaandfactryortexonrunbackfrmdeep layer in proper order: the molecular (plexi-amydaloidbodyothassociationortexpreopform),contains nonspccific afferentfibers that comearea and hypothalamus.The amygdaloid body mod.from inner parts ofthe cortexorfromthethalamusulates sensory information processing in the associ-@external granular, is a rather dense layer composedation cortex, and also participates in regulating enofsmallcells(neurons);③externalpyramidal,condocrine activity, sexual behavior, and food and watertains pyramidal cells,frequently in row formation,intake. Lesions in some areas of the amygdaloid bodywhich send association fibers to other cortical aeras:can modify, inhibit, or unleash these behaviors.@ internal granular, is usually a thin layer with cellssimilar to those in external granular layer. These cellsOtherexperiments haveshownthat the limbicareinterneuronswhich receive specificfibersfromsystem is associated with pleasure and pain. Whenthe thalamus and remain its output fibers within thecertain areas of the limbic system or the thalamus, hyinternal pyramidal,containspyramidialpothalamus, and midbrain are stimulated in animals,cortex;cells that are fewer in number but larger in size thantheir reactions indicate that they are experiencingthose in the external pyramidal layer. These cellsintense punishment.When other areas are stimulated,project axons to distal structures (eg., brain stem andthe animal reactions indicate that they are experienc-spinal cord);polymorphic (multiformorfusiform)ing extreme pleasure.Electrical stimulation of thelamina,consists ofirregularfusiformcellsgivingriseamygdaloid nucleus in humans may result in fear,to corticothalamic projections. The details of theseanxiety,or rage and aggression.Because it assumes alayers differ from one region to another.From neocor-primary function in emotions such as pain,pleasure,tex to archicortex, they change their structure from arage,fear, sorrow,sexual feelings,docility and affec-modified six layered to a four or three layered cortex,tion, the limbic system is sometimes called the “vis-for instance, the hippocampus is a primitive trilami-ceral brain" or"emotional brain"nar cortex with molecular, pyramidal, and polymor-The limbic system is concerned with: cogni-phic layers from the original external surface to thetive processes involved in memory:② controling theventricular ependyma,whereas thetransition eventsvisceral and endocrine activity; emotional expres-from hippocampus to parahippocampal gyrus changesion and genesis, together with visceral response totheir structure to four layers,five layers and six layersthe emotions, survival of individual and species.The(including prosubiculum, subiculum, presubiculum,limbic system is also known as the visceral brain be-parasubiculum)(Figs.VI-2-41)cause ofits substantial influence on visceral functionsThe cerebral cortex has been divided into cytoar-through the autonomic nervous system.chitectural areas, based on differences in the thick-ness of individual layers,neuronal morphologyin theII . Cerebral Cortexlayers, and connection of nervefiberlamination.Themost commonly employed system is the Brodmann'ssystem, Brodmann's map, which consists of approx-Histological structure of theimately 52 areas (Fig. VI-2-40). These anatomicallydefined areas have been used as a reference base forcerebral cortexthe physiologic and pathologic processes.Each cerebral hemisphere has a mantle of grey扫描全能王创建