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Neuro Exam III > 4-7 Brainstem and III, IV and VI > Flashcards

4-7 Brainstem and III, IV and VI Flashcards

1
Q

What are the 2 signalling systems that pattern the dorsoventral axis of the developing NS?

A

SHH - sonic hedgehog - motor, ventral

BMPs - bone morphogenic proteins - sensory, dorsal

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2
Q

What do the following embryological structures give rise to in the adult spinal cord:

marginal zone

mantle zone

ventricle zone

alar plate

sulcus limitans

basal plate

A

marginal zone - white matter

mantle zone - gray matter

ventricle zone - ependymal cell layer

alar plate - dorsal horns

sulcus limitans - coronal section/plane, between dorsal and ventral

(around this is lateral horns, visceral motor system)

basal plate - ventral horns

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3
Q

On the spinal cord, things are organized dorsally to ventral:

dorsal

GSA

GVA

GVE

GSE

ventral

How are these same modalities organized on a developing brainstem?

A

Imagine a line going across sulcus limitans, and rotating it 90 degrees:

Lateral GSA GVA GVE GSE medial

More complete:

SSA GSA GVA GVE SVE GSE | GSE SVE GVE GVA GSA SSA

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4
Q

In the developing brain stem, the following structures in the myelencephalon become what in the adult structure?

Roof plate

Alar plate

Basal plate

A

Myencephalon = precursor to medulla

Roof plate - choroid plexus

Alar plate - sensory nuclei for CN VII - X

Basal plate - motor nuclei for CN VII - XII

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5
Q

In the developing brain stem, the metencephalon is formed in 2 divisions. What are they?

A

Dorsal division

Ventral division

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6
Q

What does the dorsal division of the metencephalon form?

A

Alar plate forms cerebellum, develops from rhombic lip

Sensory cranial nerve nuclei (V)

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7
Q

What does the ventral division of the metencephalon form?

A

Basal pons with pontine nuclei

(doesn’t follow typical dorso-ventral patterning)

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8
Q

What does the mesencephalon give rise to in the adult brain? Where is the sulcus limitans?

A

Midbrain:

Tectum & tegmentum

Sulcus limitans at cerebral aqueduct

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9
Q

What does the alar plate of the mesencephalon give rise to?

A

Tectum of midbrain

  • corpora quadrigemina

GSA of CN V

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10
Q

What does the basal plate of the mesencephalon give rise to?

A

GSE and GVE of CN III

GSE of CN IV

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11
Q

What are the GSE of the brainstem? Where are they, relatively, and what do they contain?

A

CN III, IV, VI, XII

Generally located in dorsomedial region

Contain cell bodies of LMNs

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12
Q

How are the nuclei for CN III, IV and VI connected? Where are they located, roughly? Why is this spatial relationship important?

A

CN III, IV and VI are located near medial aspect of brainstem, but at different levels

III is up in midbrain

IV in rostral pons

VI in caudal pons

MLF can connect all nuclei easily, since they are located almost on top of each other at different levels, a fiber tract can create vergence and coordination between the different nuclei

This allows for vestibuloocular reflex, saccades, tracking, etc.

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13
Q

What does control of eye movements allow you to?

A

Shift gaze, or direct image to fovea

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14
Q

What is quick phase eye movement generated by?

A

Quick phases of nystagmus generated during vestibular or optokinetic stimulation or as automatic resetting movements in the presence of spontaneous drift of eyes

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15
Q

What is the function of the omnipause neurons?

A

Keep eyes still, allow them to focus/fixate on things

Normally, these release glycine on the PPRF

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16
Q

What is the PPRF?

A

Parapontine reticular formation

activates ipsilateral abducens nucleus

Omnipause neurons release glycine on these neurons

Disinhibition supplied from superior colliculus, and allows for gaze to shift

17
Q

How is saccades initiated?

A

Sudden burst of activity from midbrain, superior colliculus

Activates mesencephalic reticular formation (MRF)

Activated MRF will release GABA onto RIPOPN/omnipause neurons

RIPOPN neurons now turned off

Inhibition of PPRF burst neurons now off, these will now activate CN VI nucleus

18
Q

What pathways converge on the superior colliculus?

A

Frontal eye fields

Supplementary eye fields

Parietal eye fields

Dorsolateral prefrontal cortex

19
Q

What cortical areas control voluntary saccades to contralateral side?

A

FEF - area 8 and supplemental eye fields

20
Q

What cortical areas control reflexive saccades?

A

parietal eye fields

21
Q

What cortical area controls voluntary inhibition of reflexive saccades?

A

Dorsolateral prefrontal cortex

22
Q

What is the pathway for voluntary saccades?

A

Voluntary command on right side for left moving saccades

Brodman’s area 8/FEF sends fiber to midbrain and superior colliculus to synapse there

Fibers will leave and travel to/decussates at contralateral MRF

Fibers will descend to pons

Fibers will inhibit RIPOPN neurons

PPRF now able to be active

PPRF activates ipsilateral CN VI/abducens

also activates contralateral CN III/medial rectus

(double check laterality on this, my notes from Vosko aren’t adding up that well)

23
Q

What is the role of the basal ganglia in oculomotor movements?

A

Helps with tracing of familiar faces with eye movements

Needs input from SNPR

Both direct and indirect pathways involved

24
Q

What is the pathway for basal ganglia involvment in eye tracking?

A

Parietal or FEF send activating projecting neuron to striatum

striatum = caudate + putamen, has GABA-ergic neurons

Striatum projects to SNPR and inhibits it

SNPR is normally inhibiting superior colliculus, VA/VL thalamus

BG is working

VA/VL and superior colliculus is disinhibited

Direct pathway shuts down SNPR, superior colliculus, and VA/VL thalamus

Activation of superior colliculus allows for gaze shift

25
Q

What does cerebellar input to the eyes do?

A

Tells eyes how much to move, saccades to send eyes to correct position relative to your body

26
Q

What is the path of afferent/efferent cerebellar input on eye tracking?

A

Neurons from FEF or parietal eye fields will descend to pons, synapse and decussate

Fibers will enter cerebellum via middle cerebellar peduncle

Fibers will head to fastigial nucleus in flocculonodular level

Synapse there

Fibers from fastigial nucleus will head out inferior cerebellar peduncle/juxtarestiform body to ipsilateral vestibular nucleus

From medial vestibular nucleus to ipsilateral abducens nucleus

PPRF will send fibers to lateral rectus and contralateral CN III nucleus

Neuro Exam III (9 decks)

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