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CNS > Unit 6 - Cerebral White Matter > Flashcards

Unit 6 - Cerebral White Matter Flashcards

1
Q

What causes WM microstructure organisation

A

Damage to myelin, deficit in production by oligodendrocytes or change in genes that code for cell types (MAG and MOG)

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2
Q

What produces myelin

A

Oligodendrites

Concentric appearance

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3
Q

How does WM develop

A

At birth myelination is minimal

It increases dramatically during the 1st & 2nd year and continues to mature through life peaking at approx 40 yrs

then degenerates

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4
Q

What is the last to be derived

A

Association tracts (functionally speaking)

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5
Q

Striae

A

Thin bundles of fibres that pass longitudinally across the brain

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6
Q

Fascicles

A

Microscopically determined groups of fibres

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7
Q

Lamina

A

Relatively thin sheets of axons that proceed in a similar direction

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8
Q

Capsules

A

Curved sheets of fibres that partially enclose a grey matter structure

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9
Q

Tracts

A

Groups of axons subserving a similar or corresponding function

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10
Q

Radiations

A

Broad sheets of fibres that arch together to/from 1 target

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11
Q

Name for tracts that run together

A

Radiations

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12
Q

Where does the arcuate fasciculus lie

A

Within the longitudinal fasciculus

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13
Q

Commissural

A

Crossing the midline connecting cortical areas in 1 hemisphere to the other

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14
Q

Projection

A

Cortex to distant sites such as brainstem and spinal cord and vice versa

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15
Q

Association

A

Connecting cortical areas within the same hemisphere

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16
Q

Homotopic commissural fibres

A

Fibres that connect corresponding areas of cortex

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17
Q

Heterotopic

A

Fibres that connect a non-corresponding area in the contralateral hemisphere

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18
Q

main commissural fibres

A

Corpus callosum

Anterior commissure

Posterior commissure

Hippocampal commissure

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19
Q

Function of CC

A

Laterally the fibres of CC fan out into 2 wide cortical areas

Link those areas functionally related to midline - more relevant to trunk and to visual vertical meridian (than to the periphery of vision)

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20
Q

What does the rostrum of the CC continue as

A

Lamina terminalis

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21
Q

What is lamina terminalis embryonically

A

Closure point of anterior neural pore of neural tube during development

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22
Q

Synonym for genu of CC

what does it connect

A

Forceps minor

Interconnects the anterior frontal lobe, prefrontal cortices and anterior cingulate

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23
Q

Body of CC

What does it connect

A

roof of lateral ventricles between cingulum and laterally bounded by longitudinal fasciculus - interconnects precentral gyri - motor cortices, as well as insula more laterally and cingulate gyrus

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24
Q

Isthmus of CC is the location of

What does the isthmus denote

A

denotes a point of conversion during development between more posterior splenium (forceps major) - Fo

Location of commissure of fornices/hippocampal commissure

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25
Function of CC fibres anterior VS posterior to the isthmus
CC fibres anterior to the isthmus connect frontal association cortices and those of the isthmus connect precentral motor and postcentral somatosensory and Heschls, those posterior to the isthmus connect visual and association fibres of the parietooccipital cortices
26
What does the splenium connect
Posterior parietal Medial occipital Medial temporal
27
Where is there more myelination
More myelinated when connecting primary motor and somatosensory areas -and smaller and poorly myelinated when connecting association cortices (NOT PRIMARY CORTICES)
28
Overall function of CC
Facilitates inter hemispheric interaction, underlying communicating and integrating perceptual learning and volitional information - higher order cognition and emotional functioning
29
Genu as a site of lesion
Diagnostic dyspraxia - alien hand syndrome - inter-manual conflict involving 1 hand (usually left) interfering with the correct execution of movement in the other hand
30
Isthmus/splenium region lesion
Main etrangere - patients inability to recognise his left hand as his own when its in his other hand and out of the visual field
31
Splenium as a site of lesion
Optic aphasia - failure to name objects present visually
32
Where is the ant. commissure located What is its function connections
Located on lamina terminalis Reflex control of activity in the olfactory bulbs connecting them Facilitates some inter hemispheric communication between the olfactory nuclei, primary cortices of the olfactory system and the amygdalae, as well as orbital cortices ?? Facilitates communcation between the 2 accumbens nuclei (reward and addiction)
33
Where does the ant. commissure run
Crosses midline in the anterior wall of the 3rd ventricle, just rostral to the ant. fornix leading to pre and post commissural columns
34
What structure is the post. commissure a part of
Epithalamus Epithalamic commissure interconnects superior posterior brainstem nuclei bilateral pupillary reflexes in response to light
35
What does the hippocampal comissure connect
Crura of fornices Where they converge towards the midline, immediately inferior to CC Commissure connects the 2 medial temporal lobes (precebiculum, enteorhinal cortex and parahippocampal gyri but NOT hippocampal formation themselves - function is not well understood)
36
Where do most projection fibres pass through
Many fibres pass reciprocally through: The crus cerebri or cerebral peduncles (superior to pons) Pass in a compact area at the level of the basal ganglia (the IC) Relay in thalamus Reach cortex
37
Overview of fibre tracts
38
Overview of structures around the CC
39
What passes through the IC Where does it exist Inferior to IC, where do fibres pass through Superior to IC, where do fibres pass through
Majority of structures between the cerebral cortex and subcortical structures travel through the IC NOT a tract, but a compact area that tracts pass through - exists at the level of the basal ganglia Inferior to it, the fibres are passing through the CPs Superior to it, the fibres diverge to enter thalami nuclei - relay before emerging out through thalami peduncles - convey to cortex
40
Where do afferent fibres of IC arise from
thalamus and radiate to all parts of cortex - thalamic radiations, grouped into thalamic peduncles
41
Efferent fibres in IC arise from
cortical neurons and extend widely to specific portions of thalamus brainstem and spinal cord Corticotegmental Corticopontine Corticobulbar (medulla) Corticospinal
42
Ant. limb of IC connects
connects thalamus parts to cingulate and pons and thalamus to frontal cortices
43
What does the genu of the IC connect What structure is it related to
IV foramen Connects PONS and FRONTAL CORTEX - frontopontine tract Corticobulbar tract
44
Nuclei in post. limb of IC
Thalami nuclei with motor and premotor cortex and with postcentral gyri Corticospinal tract
45
Retrolenticular part of IC
Posterior to putamen/lenticular formation (putamen and GP) Fibres connecting thalamus to cortex - optic radiations and parietopontine fibres
46
Sublenticular part of IC
Inferior to lenticular formation Continuous with retrolenticular fibres and includes AUDITORY radiations
47
3 capsules
Internal - projection External - association Extreme - association
48
3 medullary lamina
Internal (within thalamus, projection) Middle Lateral
49
Define corona radiata
Collective term for all the fibre tracts connecting the brainstem to the thalamus (incl. the IC area) and those connecting thalamus and peduncles
50
4 thalamic peduncles
Anterior Superior Posterior Inferior
51
Ant. thalamic peduncle connects
separate from anterior limb of IC to interconnect the thalamus with the prefrontal and cingulate cortices
52
Sup. thalamic peduncle
separate from posterior limb of IC Corticospinal, corticopontine, corticotegmental - MOTOR FUNCTION - efferent
53
post. thalamic peduncle
separate from RETROLENTICULAR PART of the IC to interconnect the thalamus with occipital and posterior parietal and temporal lobe cortices - incorporate the geniculocalcarine tract (optic)
54
inferior thalamic peduncle
pass below the lentiform nucleus within the IC - sublenticular - to connect with the anterior temporal, orbitofrontal and insular cortices as well as the amygdala - also AUDITORY - geniculotemporal tracts
55
At what point is the transition from thalamic to cerebral peduncles
At tegmentum
56
what are the striae
Olfactory - CNI Stria medullaris Stria terminalis Medial and lateral longitudinal striae
57
Where does stria medullaris run What does it connect
Striae medullaris tracts along the medial surface of each thalami nucleus Connects the septal area - cortical area just anterior to lamina terminalis and lateral pre-optic nucleus of the thalamus and GPi with the HABENULA
58
What is the habenula implicated in
Behaviour and sleep through connections with pineal gland Pain Stress Reward Depression and anxiety
59
Where does stria terminalis run What does it connect
Courses along caudothalamic grooves where medial surface of caudate nucleus meets the thalamus on each side Prominent outflow conguit of amygdala, beginning in temporal lobe and arching with the caudate in a path to terminate rostrally in nucleus of ST - lateral to anterior columns of the fornix and dorsal to ant commissure
60
Where do the medial and lateral longitudinal striae run What do they connect
Connect dentate gyrus of the hippocampus in a path superifical to the CC with a GM - indusium grisium, terminating with the parahippocampal gyrus and continuing to diagonal band of Brocha and ultimately to amygdala
61
Where is the paraterminal gyrus
immediately anterior to lamina terminalis Inferior posterior most part of medial surface of frontal lobe
62
What are the association fibres that connect diverse regions of the same hemisphere
Cingulum bundle Superior longitudinal fasciculus (arcuate fasciculus) Inferior longitudinal fasciculus Inferior frontal longitudinal fasciculus Uncinate fasciculus
63
REVIEW: ILF IFOF UNCINATE

CNS (36 decks)

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