5 limbic system

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5 limbic system

  1. 1. THE LIMBIC SYSTEM DR.SWATI PATIL
  2. 2. LIMBIC SYSTEM• Introduction• Anatomical structures• Connecting pathways• Functions• Applied
  3. 3. INTRODUCTION• Broca –great limbic lobe• Papez –circuit of Papez• Paul D. Maclean – reintroduced term limbic• Kluver Bucy –temporal lobectomy –Extreme behavioral syndrome – Kluver Bucy syndrome Paul D. MacLean
  4. 4. FUNCTIONS OF LIMBIC SYSTEM• Integration of olfactory, visceral, somatic impulses• Control of activities necessary for survival of animal• Control of activities necessary survival of species• Emotional behaviour• Retention of recent memory
  5. 5. Cortical & Subcortical Limbic Areas
  6. 6. COMPONENTS OF LIMBIC SYSTEM• Limbic lobe• Hippocampal formation• Amygdaloid body• Connecting pathways
  7. 7. LIMBIC SYSTEM
  8. 8. OVERVIEW OF LIMBIC STRUCTURE
  9. 9. HIPPOCAMPAL FORMATION• Hippocampus proper• Dentate gyrus• Subicular complex• Entorhinal area
  10. 10. HIPPOCAMPUS• Cornu ammonis• Location :-• Pes hippocampi• Alveus• Fimbria
  11. 11. HIPPOCAMPUS
  12. 12. HIPPOCAMPUS• Trilaminar archicortex :--3 distinct fields :-CA1,CA2,CA3• CA3:- largest Pyramidal cells - receive mossy fibres• CA2 :-pyramidal cells -input from supramammillary region• CA1 :-most complex
  13. 13. • Strata within layers of hippocampus :-- Stratum oriens- Stratum pyramidalis- Stratum radiatum- Stratum lacunosum• Schaffer’s collaterals• Perforant pathway
  14. 14. DENTATE GYRUS• Crenated strip of cortex• Beaded/ toothed surface• Fimbriodentate sulcus• Gyrus fasciolaris& indusium griseum
  15. 15. LIMBIC SYSTEM
  16. 16. [
  17. 17. • Cotrex of dentate gyrus-granule cell layer(principal cells)-molecular cell layer-polymorphic layer• Mossy fibres• Fascia dentata
  18. 18. SUBICULAR COMPLEX• Subicular complex :-• Trilaminar archicortex-molecular layer-pyramidal layer:-major subcortical projections-polymorphic layer
  19. 19. ENTORHINAL CORTEX (Brodmann’s area no 28)• Location :-• Receive projections from olfactory bulb• Layer 1-6:-
  20. 20. FORNIX & FIMBRIA• FimbriaOf hippocampus• Crus of fornix : ->1 million fibres-afferent and efferents• Columns of fornix
  21. 21. HIPPOCAPMAL COMPLEX: CIRCUITARY• Excitatory pathways-perforant pathway-mossy fibres-schaffer’s collaterals• Inhibitory pathways-GABA neurons in denatate gyrus
  22. 22. AFFERENT CONNECTIONS1. Cerebral neocortex2. Septal area3. c/l hippocampus4. Nuclei in reticular formation of brain stem
  23. 23. • Entorhinal area :-follow 2 routes to hippocampus-Perforant path-Alveolar path• Fornix and fimbria :- fibres come from C/L hippocampus-thalamic and hypothalamic nuclei-ventral tegmental nuclei-locus ceruleus-raphe nuclei
  24. 24. EFFERENT CONNECTIONS • Efferents – same cortex - diencephalon - brain stem • Fornix :-largest efferents -originate in subiculum, hippocampus -Alveus – fimbria – crus of fornix – body of fornix • Parahippocampal gyrus – dorsal hippocampal commissure – hippocampal formation
  25. 25. EFFERENTS• Columns of fonix- septal area, ant part of hypothalamus, substantia innominata• Lateral dorsal thalamic nucleus – thalamus – mamillary body – ant nucleus of thalamus• Mamillotegmental fasciculus
  26. 26. PAPEZ CIRCUIT• The circuit of Papez• Ring of interconnected neurons• Input to circuit• Output to circuit• Mamillotegmental fasciculus
  27. 27. FUNCTIONS OF HIPPOCAMPUS • Retention of short term memory – long term declarative memory
  28. 28. LIMBIC SYSTEM STRUCTURE
  29. 29. AMYGDALA• Almond• Involved in Central regulation of ANS connection to hypothalamus• Controls survival fight- or-flight response of ANS• Emotional & visceral responses
  30. 30. AMYGDALA• Several group of nucleus• B/w inferior horn of lateral ventricle & lentiform nucleus• Two divisions :- -dorsomedial -ventrolateral – Basolateral - central
  31. 31. AFFERENTS OF AMYGDALA• Reciprocal connections• Subcortical afferents• Dopaminergic afferents – ventral tegmental area• Cholinergic afferents – basal forebrain nuclei• Olfactory corticomedial & non olfactory basolateral nuclei – central nuclei
  32. 32. EFFERENTS OF AMYGDALA• Stria terminalis – septal area, preoptic area, anterior hypothalamus• Medial forebrain bundle – brain stem• Ventral amygdalofugal pathway – diagonal band of broca – septal area – nucleus accumbens – dorsomedial nucleus of thalamus – prefrontal cortex
  33. 33. • Septal area – stria medullaris thalami – habenular nuclei – reticular formation – autonomic nuclei
  34. 34. Amygdala Connections Cerebral cortex Stria Olfactory system terminalis Hypothalamus ThalamusBrainstem reticular formation AMYGDALA Ventral Amygdalofugal fibers
  35. 35. FUNCTIONS OF AMYGDALA• Central and basolateral nuclei of amygdala – behavioral and emotional functions• Emotional responses• Electric stimulation – feeling of fear, general irritability, anger• Behavioral and cognitive disturbances
  36. 36. APPLIED• Kluver Bucy syndrome-complete removal of both temporal lobes-amygdaloid body, hippocampal formation-docility, lack of emotional responses, increased sexual activity (perverted), visual agnosia-Amygdaloid body lesion-Lesion of hippocampi
  37. 37. • Anxiety states-Inappropriate activity of amygdala-Panic attacks of excessive activity of sympathetic nervous system, subjective feeling of worry-Treatment – anxiolytic drugs
  38. 38. • Schizophrenia-anatomical measurements reduced in size-antipsychotics antagonise action of dopamine-parkinsonism-tardive dyskinesia
  39. 39. • Memory disorders-consolidation of new short term memory-arterial occlusion – infarction – loss of hippocampal function-transient global amnesia-head injury –damage to hippocampus – hemorrhage – anterograde amnesia
  40. 40. - B/l hippocampal lesion – major circuit of hippocampus- B/l transaction of fornix – severe amnesia• Alzheimer’s disease –- loss of cholinergic neurons of substantia innominata which project to hippocampus -ass. with degenerative changes in entorhinal cortex, hippocampus, extensive neocortical atrophy-amnesia for recently occurred events as mechanism for retention of new memory not operating

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