12- Embryo 1

Question 1

Primary axes of CNS

Answer 1

rostro-caudal axis = “Nose to tail” axis

dorso-ventral axis complicated by neural tube

Question 2

How does neural tube complciate dorso-ventral axis

Answer 2

b/c neural tube takes 80degr turn at cephalic flexure (btwn dien/mesenceph) and forms

portion of CNS above flexure (where dorsal assoc with superior and ventral assoc with inferior)

portion below flexure dorsal is towards the back

Question 3

3 main planes to view the NS

Answer 3

sagittal
coronal (frontal)
axial (transverse or horizontal)

Question 4

How is nervous system because segment into rostrocaudal segments

Answer 4

1) developing neural tube enlarges at rostral end –> 3 primary cerebral vesicles (pros, mes, rhomb)
2) primary become segmented into secondary vesicles
3) caudal to myelencephalon is early spinal cord

Question 5

what does prosencephalon vesicle become

Answer 5

pair of telencephalic vesicle + more caudal diencephalic vesicle

Question 6

what does mesencephalic vesicle become

Answer 6

mesencephalon (no segmentation further)

Question 7

what does rhombencephalon become

Answer 7

metencephalon

more caudal myelencephalon

Question 8

Cerebral vesicles are segments of ___

Answer 8

hollow neural tube

Question 9

difference btwn what vesicles develop into vs neural tube

Answer 9

vesicles = adult structures of CNS

lumen of neural tube = adult CNS architecture

Question 10

paired telencephalic vesicles have lumen and become ___

Answer 10

lateral ventricles of cerebrum

Question 11

lumen of diencephalon becomes ___

Answer 11

3rd ventricle

Question 12

mesencephalon’s lumen gives rise to ___

Answer 12

cerebral aqueduct

aqueduct of Sylvius

Question 13

lumen of rhombencephalon (both metencephalon + myelencephalon) give rise to ___

Answer 13

4th ventricle

Question 14

lumen of developing spinal cord give rise to ___

Answer 14

central canal

Question 15

Rhombencephalon is comprised of ___ which are morphologically distinct

Answer 15

8 rhombomeres

Question 16

Early in development, rhombomeres ___ but each one ___

Answer 16

resemble each other in size and # of cells but each one develops differently

Question 17

What genes expressed in rhombencephalon

these genes expressed in ___ manner meaning

Answer 17

Hox (homeobox genes)

each expressed in combinatorial manner so each has specific set of Hox genes that define each rhombomere

Question 18

what creates the different combinations of Hox genes

Answer 18

morphogen gradients in rostro-caudal and antero-posterior axis

Question 19

what does a given combination of Hox genes create?

Answer 19

actives distinct pattern of differentiation by affecting transcription –> thus each rhombomere differentiates differently

Question 20

motor neurons of ___ arise from rhombencephalon

each motor nerve originate from __

thus ___ is an early step in CN formation

Answer 20

CN 4, 5, 6, 7, 9, 10, 11, 12

originate from single rhombomere or pair of neighboring rhombomeres

Hox gene expression

Question 21

General scheme of dorsoventral patterning of neural tube into alar and basal plate

DV patterning determined by ____

Answer 21

DV patterning determed by morphogen gradients with differential expression of Hox

1) when neural plate forms neural tube, lateral ectoderm lips brought together on dorsal side
2) thus, BMPs highest on dorsal tube and Shh highest near notochord on ventral tube
3) therefore, regional diff in Hox gene expression –> diff cell pop’n

Question 22

most important morphogens in DV patterning and secreted from where and where located

Answer 22

BMPs
secreted by lateral ectoderm
located at dorsal tube

Shh
secrete by notochord
located at ventral tube

Question 23

Neural progenitor cells develop into specific populations based on ___

NT creases to separate dorsal and ventral

Ventral pop’n called __ and develop into __

Dorsal pop’n called __
and develop into __

Answer 23

position along DV axis

Ventral = basal plate = motor neurons

Dorsal = alar plate = sensory neurons

Question 24

morphogen gradients in DV patterning of the prosencephalon are ___ as those for midbrain and more caudal

Shh concentration therefore highest where?

BMP concentration highest where?

Answer 24

the same!

Shh = ventral tube near notochord

BMP = dorsal tube

Question 25

When does rostral neural tube take on 3D architecture?

Based on what?

How?

Answer 25

before telencephalic vesicles form

based on morphogen gradients

by developing 3 prolif zones (cortex dorsally, lateral ganglionic eminence, and medial ganglionic eminence)

Question 26

what are the 3 proliferative zones of rostral neural tube

Answer 26

cortex dorsally
LGE
MGE

Question 27

What happens after 3 prolif zones are formed in rostral tube

Answer 27

undergo cell proliferation, migradiation, and axon guidance to transform telencephalic vesicles into complete 3D adult brain

Question 28

what does LGE and MGE become

Answer 28

LGE and MGe split by axons of corticospinal tract

forms putamen and globus pallidus laterally

caudate nucleus medially

Question 29

what happens after telencephalic vesicles form

Answer 29

they fold over themsleves (burying part of cortex (insular)) and form C-shaped distortion of ventricles and caudate

Question 30

metencephalon becomes

Answer 30

pons and cerebellum

Question 31

myelencephalon

Answer 31

medulla oblongota

Question 32

diencephalon becomes

Answer 32

thalamus/hypothal

Question 33

telencephalon

Answer 33

cerebral cortex