T12- CNS Development

Question 1

What happens during primary neurlation

Answer 1

The primary neural tube forms from the neuroectoderm of the neural plate

Question 2

What happens during secondary neurulation

Answer 2

The secondary neural tube forms from mesodermal remains of the primative streak

Question 3

What are the steps of primary neurlation

Answer 3

1. Induction of neuroectoderm 2. Elevation of the neural folds 3. Conversion, contact, and fusion of the neural folds 4. Differentiation of surface ectoderm

Question 4

In elevation of the neural folds, (a) what is created? and (b) what importance does the notocord have?

Answer 4

(a) A distinct shape is created with the aid of cell wedging at the median hinge point (b) the notochord controls the position of the median hinge point

Question 5

When does first fusion of the neural folds occur?

Answer 5

at the 5th somite pair

Question 6

In which direction does fusion occur

Answer 6

at a cranial+caudal direction

Question 7

Prior to neuropore closure, the _____________ is in open communication with the ____________ at both cranial and caudal ends

Answer 7

neural canal; amniotic cavity

Question 8

Remanining mesenchymal cells of the ____________ occupy a midline position within the____________

Answer 8

primative streak, caudal eminence (tail bud)

Question 9

Where are primative streak mesenchymal cells located in reference to the neuropore

Answer 9

they’re located caudally to the neuropore

Question 10

What does primative streak mesenchyme condense into during secondary nerulation

Answer 10

the medullary cord

Question 11

Steps of secondary neurlation

Answer 11

1. Formation of medullary cord 2. Mesenchymal cells transition into epithelial cells 3. Canalization of epithelial cells 4. Joining of lumen of medullary cord and neural canal

Question 12

What are neuroepithelial cells

Answer 12

tall columnar cells found in the ventricular zone of the neural tube

Question 13

What does rapid proliferation of the neural tube cause?

Answer 13

(a) A psuedostratified appearance on the ventricular zone (b) An overall thickening of the NT wall (c) Change in shape and size of the neural canal

Question 14

Newly formed neuroepithelial cells differentiate into what

Answer 14

neuroblasts+glioblasts

Question 15

Where do neuroblasts and glioblasts migrate into

Answer 15

the intermediate zone

Question 16

Neuroepithelial cells that remain in the ventricular zone transition into what

Answer 16

ependymal cells

Question 17

Where does the spinal cord begin to develop

Answer 17

from the neural tube caudal to the 4th pair of somites

Question 18

Neural tube that forms the spinal cord was created by both ___________ and _________ neurulation

Answer 18

primary; secondary

Question 19

Where does sonic hedgehog influence neuroepithelial cells

Answer 19

in the ventral half of spinal grey matter

Question 20

What are bone morphogenic protiens (a) produced by? and (b) what do they influence

Answer 20

(a) produced by adjacent ectoderm (b) influence neuroepithelial cells in the dorsal half of spinal grey matter

Question 21

What does the ventral half of spinal grey matter become?

Answer 21

the basal plate

Question 22

What is the basal plate associated with?

Answer 22

motor neurons

Question 23

What does the dorsal half of spinal grey matter become?

Answer 23

the alar plate

Question 24

What is the alar plate associated with?

Answer 24

sensory neurons

Question 25

With differentiation of the spinal grey matter, what happens to the neural canal?

Answer 25

The neural canal begins to shrink in size

Question 26

What does the ventricular zone become?

Answer 26

ependymal cells which line the neural canal

Question 27

What does the intermediate zone become?

Answer 27

grey matter (nerve cell bodies)

Question 28

What does the marginal zone become?

Answer 28

white matter (nerve cell axons)

Question 29

Where is the midline roof plate located?

Answer 29

dorsally

Question 30

Where is the floor plate located?

Answer 30

ventrally

Question 31

The midline roof plate and floor plate do not contain __________ and instead serve as pathways for \_\_\_\_\_\_\_\_\_\_\_\_\_

Answer 31

neuroblasts; crossing fibers

Question 32

The notochord, which is responsible for secreting ____________ determines where it has the most influence

Answer 32

sonic hedgehog

Question 33

What happens if there is no notochord

Answer 33

no motor neurons form

Question 34

What happens if the notochord is transplanted

Answer 34

there would be a formation of an ectopic floor plate with associated motor neurons

Question 35

How is the spinal cord in the early embryo

Answer 35

it extends the entire length of the vertebral cord and all SC nerve segments lie adjacent to corresponding vertebral segments

Question 36

What happens in the growing fetus concerning vertebral elongation?

Answer 36

vertebral column elongation occurs faster than that of the SC

Question 37

Where does the brain begin to develop?

Answer 37

from the neural tube, cranial to the 4th pair of somites

Question 38

Brain developent is derived from ___________ nerulation only

Answer 38

primary

Question 39

Closure of the _______ neuropore forms three ________ brain vessicles

Answer 39

cranial; primary

Question 40

What is the cervical flexure

Answer 40

the point of transition of the spinal cord and the rhombencephalon

Question 41

Where is the midbrain flexure located?

Answer 41

in the middle of the mesencephalon

Question 42

What are the three primary brain vessicles

Answer 42

proencephalon, mesencephalon, rhombencephalon

Question 43

When does transition of primary vessicles to secondary vessicles occur

Answer 43

in the 5th week

Question 44

Histogenesis of the brain What happens to ependymal cells that migrate to the intermediate zone

Answer 44

They form deep grey matter structures near the ventricles

Question 45

Histogenesis of the brain What happens to ependymal cells that migrate to the marginal zone

Answer 45

They form the grey matter surounding the white matter in the brain

Question 46

Answer 46

(a) Telencephalon (b) Diencephalon (c) Lateral Ventricles (d) Thalami (e) Midbrain (f) Cerebral Aqueduct (g) Pons (h) Cerebellum (i) Lower part of the 4th ventricle