Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
M555 Medical Neuroscience Limbic System The Limbic System is a wide-spread system of interconnected neural structures located around the border (or “limb”) of the lateral ventricle. The Limbic System is involved in emotions, memory acquisition/consolidation and behaviors and physiological responses such as eating and reproduction that have basic survival and reproductive values. The structures of the limbic system include several regions of cerebral cortex, nuclei deep to the cortex, the hypothalamus and thalamus as well as the connections that tie all these neural structures together. Look for large areas of cerebral cortex associated with the Limbic System. cingulate gyrus medial view of left cerebral hemisphere with corpus callosum (in black) parahippocampal gyrus The medial, inferior temporal lobe is the location of the parahippocampal gyrus. Most areaes of cerebral coretx have six layers of cells and axons; the cortex of the parahippocampal gyrus has three layers. The cortex of the parahippocampal gyrus can be separated into regions of piriform cortex and entorhinal cortex. anterior piriform piriform cortex brain stem entorhinal cortex lateral ventral view of temporal lobe entorhinal There are two major centers in the medial, inferior temporal lobe in the parahippocampal gyrus. You can see them in dissected brains and in the plastic-embedded brains. amygdaloid complex = a number of nuclei grouped together as the amygdala The amygdala lies deep to the prirform cortex of the parahippocampal gyrus. hippocampal complex = a number of structures grouped together as the hippocampus The hippocampus lies deep to the entorhinal cortex of the parahippocampal gyrus. anterior piriform uncus A brain H stem entorhinal lateral Two MAjor Limbic Pathways (fornix) amygdala hippocampus amygdala figure 23-10 (5th) figure 23-15 (6th) There are two major bundles of axons associated with these structures - the stria terminalis and the fornix. They are found near the lateral ventricles. Both follow a curved path - as though they are coming up and forward from the temporal lobe. First, the smaller stria terminalis. stria terminalis A: amygdala H: hypothalamus in the diencepalon below the thalamus SN: septal nuclei (in frontal lobe near the lamina terminals and anterior commissure) Fig 23-20 (5th) Fig 23-21 (6th) The stria terminalis contains axons that carry signals from the amygdala (A). It’s not the only bundle of amygdalar efferents, but it is more easily seen than the others. Axons in the stria terminalis terminate in the a region of the telencephalon (septal nuclei) and in the hypothalamus. fornix The fornix is larger than the stria terminalis. It is subdivided into several parts. Like the stria terminalis, the parts of the fornix follow a curved path coming up and forward from the temporal lobe. body crus body crus fimbria column column hippocampus precommissural anterior fornix commissure Fimbria (near the hippocampus) Crus (both fimbria come together along midline) Body of Fornix (“hanging” from septum pellucidum beneath corpus callosum) Columns of Fornix extending downward toward anterior commissure and hypothalamus. Some axons in the columns of the fornix columns go in front of the anterior commissure to the septal nuclei (SN) and to the ventral part of the striatum (VS). This part of the fornix is called: the precommissural fornix (smaller) More axons in the columns of of the fornix go behind the anterior commissure to the hypothalamus, including the mammillary bodies (MB). This part of the fornix is called: the postcommissural fornix (larger) H: hippocampus Another major connection in the limbic system extends from the mammillary bodies to the anterior nucleus of the thalamus. This connection is called the mammillothalamic tract. The anterior nucleus of the thalamus projects to the cingulate gyrus. interventricular foramen anterior commissure fornix body fornix column anterior nucleus mammillothalamic tract hypothalamus septum pellucidum corpus callosum hippocampal commissure Important structures amygdala anterior commissure (as a point of reference) anterior nucleus of thalamus cingulate gyrus (not labeled on figures) hippocampus hypothalamus mammillothalamic tract parts of the fornix 9fimbria, crus, body, column) fornix body fornix column fornix crus fimbria alveus hippocampus don’t be concerned with alveus hippocampal commissure interventricular foramen septum pellucidum You should also be able to identify these structures. stria terminalis stria terminalis ? 5 4 13 6 6 5 7 15 8 10 1 2 3 19 9 8 12 3 8 11 11 ? 12 ? 12 14 ? 16 17 ?4 1 18 hypothalamus figure 23-21 (5th) figure 23-20 (6th) 1 10 2 11 3 12 5 13 14 6 15 7 16 8 9 17 18 19