Development of the CNS

Question 1

Gastrulation is marked by the generation of which structure?

Answer 1

The primitive streak and notochord

Question 2

What is the role of the notochord in the embryo and in adults?

Answer 2

Embryo: directs conversion of ectoderm into neurectoderm
Adult: NO function

Question 3

Briefly explain how the neural tube develops from the neural plate

Answer 3

1. The lateral edges of the neural plate elevate
2. The mid-region of the plate is depressed, forming the neural groove
3. Neural folds approach each other in the midline and fuse

Question 4

By what day is the neural tube completely closed during embryonic development?

Answer 4

Day 28-32

Question 5

Defects in what are responsible for common birth defects of the nervous system (neural tube defects)?

Answer 5

Neuropores (anterior and posterior)

Question 6

Cranial (anterior neuropore) neural tube defects result in _________

Answer 6

Anencephaly- incompatible with life

Question 7

Caudal (posterior neuropore) neural tube defects result in _________

Answer 7

Spina bifida

Question 8

Where does spina bifida most commonly occur?

Answer 8

Lumbosacral region

Question 9

How can neural tube defects be diagnosed in utero?

Answer 9

Raised maternal serum alpha-fetoprotein

Ultrasound Screening

Question 10

Deficiency in _________ has been related to neural tube defects

Answer 10

Folic acid

Question 11

The cranial neuroectoderm tube initially has how many dilations?
From these dilations how many are formed?

Answer 11

3 dilations, then 5 dilations

Question 12

What are the names given to the three dilations of the cranial neuroectoderm tube ?

Answer 12

Prosencephalon - forebrain
Mesencephalon - midbrain
Rhombencephalon - hindbrain

Question 13

What do these 3 dilations become after the neural tube closes in the 4th week?

Answer 13

Primary brain vesicles

Question 14

At 5 weeks of development, what are the names given to the secondary brain vesicles formed from the initial 3 primary brain vesicles?

Answer 14

1.Telencephalon
2.Diencephalon
(from prosencephalon)

3.Mesencephalon
(from mesencephalon)

4.Metencephalon
5.Myelencephalon
(from rhombencephalon)

Question 15

What are the mature derivatives that develop from each of the secondary brain vesicles?

Answer 15

Cerebral hemispheres
(from telencephalon)

Thalamus
(from diencephalon)

Midbrain
(from mesencephalon)

Pons, cerebellum
(from metencephalon)

Medulla
(from myelencephalon)

Question 16

What causes the neural tube to fold up?

What are produced as a result?

Answer 16

The cranial neural tube exceeds available space linearly.

Flexures are produced

Question 17

What are the name given to the flexures and where are they found?

Answer 17

Cervical flexure - spinal cord-hindbrain junction

Cephalic flexure - midbrain region

Question 18

What structure connects the III and IV ventricles?

Answer 18

Cerebral aqueduct

Question 19

What defect can occur when there is blockage of the ventricular system?
How is this treated?

Answer 19

Hydrocephalus

Using a shunt

Question 20

Which structures of the neural tube regulate dorsal and ventral patterning?

Answer 20

Roof and floor plates

Question 21

What is the name given to the structure that separates the sensory and motor nuclei in the developing neural tube?

Answer 21

Sulus limitans

Question 22

The roof plate is known as what?
The floor plate is known as what?
What type of innervation are they each responsible for?

Answer 22

Roof- Alar plate
Sensory

Floor- Basal plate
Motor