5 limbic system
TRANSCRIPT
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THE LIMBIC SYSTEM
DR.SWATI PATIL
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LIMBIC SYSTEM
• Introduction• Anatomical structures• Connecting pathways• Functions• Applied
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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
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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
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Cortical & Subcortical Limbic Areas
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COMPONENTS OF LIMBIC SYSTEM • Limbic lobe• Hippocampal formation• Amygdaloid body• Connecting pathways
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LIMBIC SYSTEM
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OVERVIEW OF LIMBIC STRUCTURE
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HIPPOCAMPAL FORMATION
• Hippocampus proper• Dentate gyrus• Subicular complex• Entorhinal area
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HIPPOCAMPUS
• Cornu ammonis• Location :-• Pes hippocampi• Alveus • Fimbria
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HIPPOCAMPUS
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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
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• Strata within layers of hippocampus :-
- Stratum oriens- Stratum pyramidalis- Stratum radiatum- Stratum lacunosum• Schaffer’s collaterals• Perforant pathway
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DENTATE GYRUS
• Crenated strip of cortex• Beaded/ toothed
surface• Fimbriodentate sulcus• Gyrus fasciolaris& indusium griseum
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LIMBIC SYSTEM
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[
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• Cotrex of dentate gyrus-granule cell
layer(principal cells)-molecular cell layer-polymorphic layer
• Mossy fibres• Fascia dentata
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SUBICULAR COMPLEX
• Subicular complex :-• Trilaminar archicortex-molecular layer -pyramidal layer:-major
subcortical projections-polymorphic layer
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ENTORHINAL CORTEX(Brodmann’s area no 28)
• Location :-• Receive projections
from olfactory bulb• Layer 1-6:-
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FORNIX & FIMBRIA
• FimbriaOf hippocampus• Crus of fornix : ->1
million fibres -afferent and efferents• Columns of fornix
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HIPPOCAPMAL COMPLEX: CIRCUITARY
• Excitatory pathways-perforant pathway-mossy fibres-schaffer’s collaterals
• Inhibitory pathways-GABA neurons in denatate
gyrus
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AFFERENT CONNECTIONS
1. Cerebral neocortex2. Septal area3. c/l hippocampus4. Nuclei in reticular
formation of brain stem
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• 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
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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
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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
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PAPEZ CIRCUIT
• The circuit of Papez• Ring of
interconnected neurons
• Input to circuit• Output to circuit• Mamillotegmental
fasciculus
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FUNCTIONS OF HIPPOCAMPUS• Retention of short term
memory – long term declarative memory
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LIMBIC SYSTEM STRUCTURE
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AMYGDALA
• Almond• Involved in Central
regulation of ANS connection to hypothalamus
• Controls survival fight-or-flight response of ANS
• Emotional & visceral responses
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AMYGDALA
• Several group of nucleus• B/w inferior horn of lateral
ventricle & lentiform nucleus
• Two divisions :- -dorsomedial -ventrolateral – Basolateral - central
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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
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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
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• Septal area – stria medullaris thalami – habenular nuclei – reticular formation – autonomic nuclei
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Amygdala Connections
Cerebral cortexOlfactory system
ThalamusBrainstem reticular formation
Hypothalamus
AMYGDALA
Striaterminalis
Ventral Amygdalofugalfibers
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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
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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
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• Anxiety states-Inappropriate activity of amygdala-Panic attacks of excessive activity of sympathetic
nervous system, subjective feeling of worry-Treatment – anxiolytic drugs
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• Schizophrenia-anatomical measurements reduced in size-antipsychotics antagonise action of dopamine-parkinsonism-tardive dyskinesia
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• 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
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- 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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