Lecture 17 Nervous System Dev.II

Question 1

Topographical arrangement of myelecephalon is almost identical to spinal cord, what is the major change?

Answer 1

Pronounced expansion of the roof plate to form the thin roof over the fourth ventricle

Question 2

What genes are responsible for differentiation of specific nuclei in myelencephalon?

Answer 2

Hox

Question 3

What do the mutations weaver and reeler have to do with building of cerebral cortex?

Answer 3

Weaver is a mutation in a mouse with specific behavioral defects related to abnormal function of cerebellum-defect in radial glial cells.

Reeler is abnormal behaavor in absence of nrmal cortical layering.

Question 4

What is the relation of reelin to reeler?

Answer 4

Reelin is the defective extracellular protein found in the mutant reeler

Question 5

Relate columnar radial units to organization of cerebral cortex.

Answer 5

Radial units are the six layers of grey matter that form the cerebrum. They migrate up radial glial cells laying down each layer of neurons from largest to smallest.

Question 6

Cerebellum forms in region of rhombic lips. Rhombic lips are product of what inductive interaction?

Answer 6

Roof plate and neural tube via BMP signaling

Question 7

What are major derivatives of metencephalon?

Answer 7

Pons (basal plate) and Cerebellum (alar plate)

Depends on FGF-8 from isthmic organizer

Question 8

Review the migration of cells that form the cortex in cerebellar primordium.

Answer 8

Granule cells migrate anteriorly along dorsal region of rhombomere 1
Granule cells migrate interiorly through Purkinjie layer
Purkinje cells migrate radially through granule cells

Question 9

What are superior cerebellar peduncles

Answer 9

massive fiber bundles between cerebellum and mesencephalon

Question 10

What are major derivatives of the alar plates of the mesencephalon?

Answer 10

Tectum (corpora quadrigemina): Superior and inferior colliculi

Question 11

Where is Otx-2 located and how is it related to shh?

Answer 11

Confines Shh to the basal part of midbrain

Question 12

Where do cerebral peduncles form and function?

Answer 12

Ventrolateral region of the mesencephalon and they carry fibers between the cerebral hemispheres and the spinal cord

Question 13

What are major derivatives of the diencephalon?

Answer 13

epithalamus, thalamus, and hypothalamus

Question 14

What are the three patterning centers in the forebrain and their signaling molecules?

Answer 14

Rostral patterning center (FGF-8)

Dorsal patterning center (BMP’s and Wnt’s)

Ventral patterning center (Shh)

Question 15

Describe formation of corpus striatum and corpus callosum.

Answer 15

The base of each telencephalic vesicle thickens to form corpus striatum, dorsal to thalamus it becomes C shaped. Many fiber tracts converge here.

Corpus Callosum is the third commissure to shape in the lamina terminalis and most important connection btw right and left halves. Complete by 115 days. EMX2 mutation leads to split brain (schizencephaly)

Question 16

Arnold-Chiari malformation and relation to hydrocephalus?

Answer 16

Specific malformation leading to Hydrocephalus, where parts of cerebellum herniate into foramen magnum and prevent escape of CSF from skull.

Question 17

What is rhinecephalon?

Answer 17

There is a decrease in the prominence of it as the cerebrum grows. Oldest and most primitive area in the telencephalon, heavily involved in smell.

Question 18

What is archicortex?

Answer 18

Rhinencephalon the oldest and most primitive component of the telencephalon

Question 19

What is neocortex?

Answer 19

Morphologically dominant cerebral hemispheres. As development occurs neocortex takes over as the component of most of brain mass.

Question 20

Relate cranial nerves to pharyngeal pouches and modalities?

Answer 20

CN V, VII, IX, and X and VIII suppply pharynegeal arches

Question 21

Why is CN II not true nerve?

Answer 21

CN I and II are not considered true because they are extensions of brain tracts

Question 22

Origin of cranial nerve ganglia?

Answer 22

Motor nerves developed from ventral roots and sensory come from neural crest and ectodermal placodes.

Question 23

Define Rachischisis.

Answer 23

Closure defect of spinal cord

brain closure defect is cranioschisis

Question 24

What substance when present in amniotic fluid in elevated amounts can be diagnostic of closure defects?

Answer 24

a-fetoprotein

Question 25

Order closure defects from least to most serious.

Answer 25

Spina Bifida Occulata: spinal cord meninges in place but neural arch incomplete, tuft of hair over defect

Meningocele: missing duramater arachnoid bulges beneath skin

Myelomeningocele: spinal cord bulges into subarachnoid space

Raschischisis: failure of neural folds to close

Question 26

Functional regions in spinal cord and brain:

Answer 26

Alar Plate (Afferent): general somatic, special visceral afferent, General visceral afferent

Basal Plate (Efferent): General visceral efferent Special visceral efferent General somatic efferent

Question 27

Myelencephalon derivitives?

Answer 27

Medulla Oblongata