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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
Q

Function of CC fibres anterior VS posterior to the isthmus

A

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

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26
Q

What does the splenium connect

A

Posterior parietal

Medial occipital

Medial temporal

27
Q

Where is there more myelination

A

More myelinated when connecting primary motor and somatosensory areas -and smaller and poorly myelinated when connecting association cortices (NOT PRIMARY CORTICES)

28
Q

Overall function of CC

A

Facilitates inter hemispheric interaction, underlying communicating and integrating perceptual learning and volitional information - higher order cognition and emotional functioning

29
Q

Genu as a site of lesion

A

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
Q

Isthmus/splenium region lesion

A

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
Q

Splenium as a site of lesion

A

Optic aphasia - failure to name objects present visually

32
Q

Where is the ant. commissure located

What is its function

connections

A

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
Q

Where does the ant. commissure run

A

Crosses midline in the anterior wall of the 3rd ventricle, just rostral to the ant. fornix leading to pre and post commissural columns

34
Q

What structure is the post. commissure a part of

A

Epithalamus

Epithalamic commissure

interconnects superior posterior brainstem nuclei

bilateral pupillary reflexes in response to light

35
Q

What does the hippocampal comissure connect

A

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
Q

Where do most projection fibres pass through

A

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
Q

Overview of fibre tracts

A
38
Q

Overview of structures around the CC

A
39
Q

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

A

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
Q

Where do afferent fibres of IC arise from

A

thalamus and radiate to all parts of cortex - thalamic radiations, grouped into thalamic peduncles

41
Q

Efferent fibres in IC arise from

A

cortical neurons and extend widely to specific portions of thalamus brainstem and spinal cord

Corticotegmental

Corticopontine

Corticobulbar (medulla)

Corticospinal

42
Q

Ant. limb of IC connects

A

connects thalamus parts to cingulate and pons and thalamus to frontal cortices

43
Q

What does the genu of the IC connect

What structure is it related to

A

IV foramen

Connects PONS and FRONTAL CORTEX - frontopontine tract

Corticobulbar tract

44
Q

Nuclei in post. limb of IC

A

Thalami nuclei with motor and premotor cortex and with postcentral gyri

Corticospinal tract

45
Q

Retrolenticular part of IC

A

Posterior to putamen/lenticular formation (putamen and GP)

Fibres connecting thalamus to cortex - optic radiations and parietopontine fibres

46
Q

Sublenticular part of IC

A

Inferior to lenticular formation

Continuous with retrolenticular fibres and includes AUDITORY radiations

47
Q

3 capsules

A

Internal - projection

External - association

Extreme - association

48
Q

3 medullary lamina

A

Internal (within thalamus, projection)

Middle

Lateral

49
Q

Define corona radiata

A

Collective term for all the fibre tracts connecting the brainstem to the thalamus (incl. the IC area) and those connecting thalamus and peduncles

50
Q

4 thalamic peduncles

A

Anterior

Superior

Posterior

Inferior

51
Q

Ant. thalamic peduncle connects

A

separate from anterior limb of IC to interconnect the thalamus with the prefrontal and cingulate cortices

52
Q

Sup. thalamic peduncle

A

separate from posterior limb of IC

Corticospinal, corticopontine, corticotegmental - MOTOR FUNCTION - efferent

53
Q

post. thalamic peduncle

A

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
Q

inferior thalamic peduncle

A

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
Q

At what point is the transition from thalamic to cerebral peduncles

A

At tegmentum

56
Q

what are the striae

A

Olfactory - CNI

Stria medullaris

Stria terminalis

Medial and lateral longitudinal striae

57
Q

Where does stria medullaris run

What does it connect

A

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
Q

What is the habenula implicated in

A

Behaviour and sleep through connections with pineal gland

Pain

Stress

Reward

Depression and anxiety

59
Q

Where does stria terminalis run

What does it connect

A

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
Q

Where do the medial and lateral longitudinal striae run

What do they connect

A

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
Q

Where is the paraterminal gyrus

A

immediately anterior to lamina terminalis

Inferior posterior most part of medial surface of frontal lobe

62
Q

What are the association fibres that connect diverse regions of the same hemisphere

A

Cingulum bundle

Superior longitudinal fasciculus (arcuate fasciculus)

Inferior longitudinal fasciculus

Inferior frontal longitudinal fasciculus

Uncinate fasciculus

63
Q

REVIEW:

ILF

IFOF

UNCINATE

A

CNS (36 decks)

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