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Limbic System


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Limbic System

  1. 1. Limbic system By Prof. Adel Abdel Aziz <ul><li>It is formed of groups of nuclei connected together by fiber bundles. </li></ul><ul><li>Nuclei of the limbic system : </li></ul><ul><li>1. Limbic lobe : formed of the cingulated gyrus, parahippocampal gyrus and the uncus . </li></ul><ul><li>2. Hippocampus : is continuous externally with the parahippocampal gyrus. </li></ul><ul><li>3. Hypothalamus : especially the mamillary bodies. </li></ul><ul><li>4. Thalamic nuclei : anterior and medial nuclei. </li></ul><ul><li>5. The prefrontal cortex (the personality center). </li></ul><ul><li>6. Amygdaloid nucleus . </li></ul><ul><li>7. Septal area (medial olfactory area): below the rostrum. </li></ul><ul><li>8. Habenular nucleus . </li></ul>
  2. 2. Cingulate gyrus Body of fornix Lingual gyrus Isthmus of cingulate gyrus Column of fornix Uncus Collateral sulcus Parahippocampal gyrus Crus of fornix Fimbria Dentate gyrus Splenium
  3. 3. Uncus Parahippocampal gyrus Isthmus of cingulate gyrus Lingual gyrus Splenium Collateral sulcus
  4. 4. Fiber bundles of limbic system <ul><li>1. Fornix : it arises from the hippocampus and terminates in the mamillary body. The fornix is formed of 4 parts: </li></ul><ul><li>a. Fimbria : is the continuation of alveus which is formed of axons of the neurons of the hippocampus and passes along its medial border. </li></ul><ul><li>b. Crus of the fornix: is the continuation of the fimbria below the splenium. </li></ul><ul><li>c. Body of the fornix: the two crura fuse to form the body of the fornix. </li></ul><ul><li>d. Anterior column of the fornix: each one terminates in the mamillary body. </li></ul><ul><li>2. Cingulum : is the fiber bundle of the limbic lobe. </li></ul><ul><li>3. Mamillothalamic tract : connects the mamillary body with the anterior thalamic nucleus. </li></ul><ul><li>4. Stria terminalis : it begins in the septal area and in the habenular nucleus. </li></ul>
  5. 5. Pes hippocampus Dentate gyrus Hippocampus Fimbria Columns of fornix Corpus callosum Head of caudate Septum pellucidum Collateral trigone Thalamus
  6. 6. Anterior column of fornix Body of fornix Crus of fornix Pes hippocampus Hippocampus Fimbria Dentate gyrus Splenium Stria terminalis Inf. horn of lat. vent. Commissure of fornix Head of caudate Corpus callosum Thalamus
  7. 7. Anterior fornix fornix
  8. 8. Connections <ul><li>Afferent connections : </li></ul><ul><li>1. Fibers arise from the cingulated gyrus pass to the hippocampus . </li></ul><ul><li>2. Fibers from hippocampus of one side pass to hippocampus of the other side along the fornix. </li></ul><ul><li>3. Fibers arise from the parahippocampal and dentate gyri pass to hippocampus . </li></ul><ul><li>4. Fibers arise from the olfactory association cortex pass to the hippocampus . </li></ul><ul><li>Efferent connections : </li></ul><ul><li>The fibers of the fornix are distributed to: </li></ul><ul><li>1. Fibers pass to the anterior commissure to the mamillary body and anterior part of hypothalamus . </li></ul><ul><li>2. Fibers pass to the anterior commissure to end in the anterior nuclei of thalamus . </li></ul><ul><li>3. Fibers pass to the anterior commissure to enter the tegmentum of the midbrain . </li></ul><ul><li>4. Fibers join the habenular nuclei . </li></ul>
  9. 9. Functions of the limbic system <ul><li>1. Recent memory : the hippocampus plays a role in remembering the recent events. </li></ul><ul><li>2. Emotional behavior : it plays a role in anger, fear, and emotional behavior associated with sexual behavior. </li></ul><ul><li>Malfunction of the limbic system </li></ul><ul><li>The malfunction is involved in psychiatric disorder, including schizophrenia , depression , and senile dementia . Antipsychotic drugs block limbic dopamine receptors. </li></ul><ul><li>Lesions </li></ul><ul><li>1. Lesion in the hippocampus causes loss of the recent memory. </li></ul><ul><li>2. In Alzheimer's disease , there is extensive degeneration in the hippocampus. </li></ul><ul><li>3. Lesions in the amygdaloid nucleus cause loss of the aggressive behavior, fear and anger . </li></ul>
  10. 10. Part Function Amygdala AGGRESSION and FEAR Cingulate gyrus AUTONOMIC FUNCTION Hippocampus RECENT MEMORY Hypothalamus ENDOCRINE FUNCTION Mammillary body LONG MEMORY Nucleus accumbens ADDICTION Prefrontal area PERSONALITY Parahippocampus SPATIAL MEMORY
  11. 11. <ul><li>Degenerative disease of the brain of unknown cause. </li></ul><ul><li>Diffuse atrophy of cerebral cortex. </li></ul><ul><li>Middle to late life. </li></ul><ul><li>Genetic predisposition. </li></ul><ul><li>Senile Plaques. </li></ul><ul><li>Manifestations include: </li></ul><ul><ul><li>complete disorientation. </li></ul></ul><ul><ul><li>deterioration of speech. </li></ul></ul><ul><ul><li>restlessness. </li></ul></ul><ul><ul><li>Loss of RECENT MEMORY ( HIPPOCAMPUS ) </li></ul></ul>