Nervous System Development

Question 1

In the brain what is the white matter and what is the gray matter?

Answer 1

Gray:

• basal nuclei and other nuclear groups
• in the cerebrum and cerebellum, additional external areas of gray matter, the cortices, are built in top of the myelinated white matter tracts

White:
-myelinated fiber tracts throughout various arts of the brain that lie superficial to the deep gray matter

Question 2

What is a true cortex?

Answer 2

• consists of multiple layers of gray matter (typically 6 in the cerebral cortex)
• a true cortex is built from the inside out with the most superficial layers being added last

Question 3

What are some exceptions to the definition of a true cortex?

Answer 3

• neuronal migration in the building of the cerebellar cortex occurs parallel to the surface (rather than perpendicular) in the early stages
• the cerebellar cortex and some areas of the cerebral cortex consist of 3 layers
• some parts of the cerebral cortex are built from the outside to inside

Question 4

What are some characteristics of radial glial cells?

Answer 4

• thought to be a subdivision of astrocytes
• they are located in the ventricular/ependymal zone
• each one extends a long process that passes through the intermediate zone, cortical plate, and marginal zone to the surface of the brain

Question 5

What are the role of glial cells in the building of a cortex?

Answer 5

-migrating bipolar neurons use the long process as a guiding mechanism to reach the surface where they can begin to layer the cortex

Question 6

The topographical arrangement of the myelencephalon is almost identical to what other structure?

Answer 6

Spinal cord

Question 7

What is the major topographical change of myelencephalon from the spinal cord?

Answer 7

-pronounced expansion of the roof plate to form the thin roof over the fourth ventricle

Question 8

Expression of which set of genes seems to be responsible for the differentiation of specific nuclei in the myelencephalon?

Answer 8

-Hox genes

Question 9

What are the major derivatives of the metencephalon?

Answer 9

• pons (basal plate)

- cerebellum (alar plate)

Question 10

The cerebellum forms in the region of what?

Answer 10

-rhombic lips (rhombomeres 1-8)

Question 11

The rhombic lips are the product of what inductive interaction?

Answer 11

-roof plate and neural tube via BMP signaling

Question 12

Describe how the cells that form the cortex in the cerebellar primordium migrate.

Answer 12

• granule cells migrate anteriorly along the dorsal region of rhombomere 1
• granule cells migrate inferiorly through the Purkinje layer
• Purkinje cells migrate radially through granule cells

Question 13

What are the superior cerebellar peduncles?

Answer 13

-massive fiber bundles between the cerebellum and the mesencephalon

Question 14

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

Answer 14

-tectum (corpora quadrigemina)
+superior colliculi
+inferior colliculi

Question 15

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

Answer 15

-it confines Shh to the basal part of the midbrain

Question 16

Where do cerebral peduncles form and what is their function?

Answer 16

• ventrolateral region of the mesencephalon

- they carry fibers between the cerebral hemispheres and the spinal cord

Question 17

What are the major derivatives of the diencephalon?

Answer 17

-epithalamus, thalamus, hypothalamus

Question 18

What are the three patterning centers in the forebrain?

Answer 18

• rostral patterning center (FGF-8)
• dorsal patterning center (BMPs and Wnts)
• ventral patterning center (Shh)

Question 19

What is rachischisis?

Answer 19

• developmental birth defect involving the neural tube
• posterior neuropore fails to close leaving the spinal cord not fully formed and exposed
• patients have sensory and motor defects

Question 20

Where is spinal cord gray matter located?

Answer 20

-centrally located in the form of anterior, posterior, and lateral horns situated around the central canal