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NEUR532 > Limbic System > Flashcards

Limbic System Flashcards

1
Q

what does the limbic system do?

A

-Brings together components of the cerebral hemispheres and the diencephalon

-The limbic system is concerned with memory and with visceral and motor responses involved in defensive and reproductive behaviours

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2
Q

describe the limbic lobe

A

-Ring of grey matter on the medial aspect of the each hemisphere
–Parahippocampal and cingulate gyri
–Septal area

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3
Q

What does the limbic system include?

A

-Limbic lobe
–Hippocampus
–Dentate gyrus
–Amygdaloid body
–Hypothalamus
–Anterior thalamus

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4
Q

how does the hippocampus develop? and what does it come to occupy?

A

-by a process of continuing the expansion of the medial edge of the temporal lobe
-comes to occupy the floor of the temporal horn of the lateral ventricle
-In the mature brain the parahippocampal gyrus on the external surface is continuous with the concealed hippocampus

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5
Q

What is the alveus of the hippocampus

A

-layer of white matter on the ventricular surface
–Forms the fimbria
–Continues to the crux of the fornix

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6
Q

describe the surface of the dentate gyrus of the hippocampus

A

-surface is toothed

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7
Q

describe the subiculum of the hippocampus

A

Transition from 3 layered hippocampus to the six layered parahippocampus

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8
Q

what are the 3 main areas of the hippocampus?

A

-CA1 (cornu ammonis)
-CA1 is adjacent to the subiculum

-CA2

-CA3
-CA3 is near the dentate gyrus

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9
Q

What are the 3 layers of the hippocampal cortex?

A

-pyramidal cell layer (stratum pyamidale)
-molecular layer
-polymorphic layer (stratum oriens)

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10
Q

describe the pyramidal layer of the hippocampus

A

-Large pyramidal neurons
-Principle cells of the hippocampus
-Dendrites extend into the molecular layer
-Axons traverse the alveus and fimbria
-Branches are called the schaffer collaterals pass through the polymorphic layer
-Synapse with dendrites of other pyramidal cells in the molecular layer

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11
Q

describe the molecular layer of the hippocampus

A

-Interacting dendrites and axons

-Located in the centre of the hippocampus surrounding the hippocampal sulcus

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12
Q

describe the polymorphic layer of the hippocampus

A

-Similar to layer 6 of neocortex
-Located beneath the alveus and contains axons, dendrites and interneurons

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13
Q

what are the 3 layers of the dentate gyrus

A

-granule cell layer
-mossy fibres
-hilus

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14
Q

Describe the granule cell layer of the dentate gyrus

A

-Small neurons
-principle cells of the dentate gyrus
-Region of adult neurogenesis

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15
Q

describe the mossy fibres of the dentate gyrus

A

-Efferent fibres of the dentate gyrus
-Many branches that synapse with the principle cells in CA3 and CA2

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16
Q

describe the hilus layer of the dentate gyrus

A

-Contains the axons of the granule cells and interneurons

17
Q

what are the main afferent connections of the hippocampus

A

-Cerebral cortex
-Septal area
-Contralateral hippocampus
-Various brainstem nuclei

18
Q

describe the cortical afferent connections of the hippocampus

A

-Largest contingent of fibres is from the entorhinal cortex
-Follow two routes to the hippocampus

19
Q

describe the perforant path

A

-From entorhinal cortex through the subiculum across the hippocampal sulcus to the dentate gyrus

20
Q

describe the alvear path

A

-Traverses the subcortical white matter to end in the hippocampus

21
Q

Describe the entorhinal cortex

A

-Part of the primary olfactory area
-Also receives association fibres from the neocortex of the temporal lobe
-Which in turn communicates with various sensory regions of neocortex
-Through these connections via the perforant and alvear paths the hippocampal formation is informed of all sensory information as well as higher brain functions

22
Q

describe the connections of the contralateral hippocampus

A

-commissural fibres cross the midline at the hippocampal commissure

23
Q

describe the septal area afferents

A

-Septal and basal forebrain cholinergic nuclei via the fimbria-fornix (cholinergic and GABAergic)

24
Q

describe the afferent connections from brainstem to hippocampus

A

-Ventral tegmental area (dopamine)
-Locus coeruleus (noradrenalin)
-Raphe nuclei (serotonin)

25
Q

describe the efferent connections of the hippocampus

A

-Connections through which the hippocampal formation receives information from the entorhinal area and neocortex are paralleled by reciprocal connections
-Descending projections to diencephalon and brainstem via the fimbria-fornix

26
Q

describe the fornix

A

-Contains around 1 million myelinated axons
-Most from the subiculum rest from hippocampus or afferents to the hippocampal formation
-Efferent fibres first traverse the alveus on the way to the fimbria
-Fimbria continues to the crus of the fornix
-The crus curves around the thalamus and joins to form the body of the fornix
-Above the third ventricle the body of the fornix separates into the columns
-Columns innervate the septal area anterior hypothalamus substantia innominata, lateral dorsal thalamus and the mammillary bodies

27
Q

what are the afferents to the circuit of papez

A

-Neocortex

-Thalamus

-Septal area

-Reticular formation:
–Raphe nuclei
–Ventral tegmental area
–Catacholamine nuclei

28
Q

what are the efferents from the circuit of papez

A

-Neocortex

-Reticular formation:
– Raphe nuclei
– Ventral tegmental area
– Catacholamine nuclei

-Brainstem/spinal cord:
– Solitary nucleus
– Dorsal nucleus of the vagal nerve
– Autonomic nuclei of the spinal cord

29
Q

what is the circuit of papez?

A

going downwards is the circuit

-Entorhinal cortex area of the parahippocampal gyrus
-VIA Perforant and alvear pathway
-Hippocampal formation
-VIA Fimbria-fornix
-Mammilary body
-VIA Mammilothalamic fasciculus
- Anterior thalamic nuclei
-VIA Internal capsule
-Cingulate gyrus
-VIA Cingulum
-Entorhinal cortex

30
Q

what is the circuit of papez for?

A

Ring of interconnected nuclei involved in emotion and emotional expression

31
Q

describe the amygdaloid body

A

-Several nuclei situated between the anterior end of the temporal horn of the lateral ventricle and the ventral surface of the lentiform nucleus

-Corticomedial group:
–Dorsomedial division of the amygdaloid body, blends in with the cortex of the uncus
–Afferent fibres come from the olfactory bulb

  • Ventrolateral division:
    – Basolateral
    – Central:
  • No input from olfactory bulb
  • Connect with the corticomedial group and entorhinal cortex
  • Included in the limbic system
32
Q

what are the reciprocal connections with cortex from basolateral amygdala

A

-Frontal
–Temporal
–Cingulate gyrus

33
Q

what are the subcortical connections of basolateral amygdala

A

– Thalamus – intralaminar nuclei

– Catecholamine nuclei

– Raphe nuclei – serotonin

– Parabrachial nuclei – substance P

– Ventral tegmental area - dopamine

– Basal forebrain nuclei – acetylcholine

34
Q

what are the afferents of central nuclei of amygdala

A

-Receives afferents from the corticomedial and basolateral nuclei

35
Q

what are the reciprocal connections with cortex of central nuclei of amygdala

A

– Prefrontal
– Temporal
– Anterior cingulate gyrus

36
Q

what are the efferent connections of central nuclei of amygdala

A

-Septal area, preoptic area, anterior hypothalamus
– Via the stria terminalis

  • Vagus nerve and the solitary nucleus
    – Via the medial forebrain bundle
  • Nucleus accumbens and the dorsomedial nucleus of the thalamus
    –Via the ventral amygdalofugal pathway
37
Q

describe the habenular nuclei connections

A

-Habenular nuclei
–Via the stria medullaris thalami

-Habenula innervates the interpeduncular nucleus
–Via the habenulointerpeduncular tract

-Habenular nuclei also receive afferents from globus pallidus providing a pathway by which the
neocortex can influence autonomic function

38
Q

What are the functions of the amygdaloid body?

A

-Central and basolateral nuclei are chiefly responsible for the behavioural and emotional functions of the limbic system

-Emotion – activities of the brain evoked by incentives for survival

-strong affective reactions such as:
–Fear and anger
–Sexual behaviour

-Electrical stimulation of the amygdala:
–Increased heart rate and respiration
–Suppression of salivation
–Pupillary dilation
–Changes in facial expression

-Therefore, the amygdala may give rise to the automatic and somatic accompaniments of fear and anxiety

NEUR532 (14 decks)

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