Development of Brain and Spinal Cord

Question 1

What is the last system to develop

Answer 1

CNS

Question 2

When does Myelination of the Brain begins

Answer 2

Third trimester , week 28 to 40

Question 3

Brain development in the prenatal months are under which type of control

Answer 3

Genetic and environmental control

Question 4

What are the primary Vesicles that arise from the neural tube at the cranial end

Answer 4

1- Prosencephalon
2- Mesencephalon
3- Rhombencephalon

Question 5

The Prosencephalon forms what ( secondary vesicles )

Answer 5

1- Telencephalon

2- Diencephalon

Question 6

The mesencephalon forms what ( secondary vesicles )

Answer 6

Stays the same , mesencephalon

Question 7

The Rhombencephalon form what ( secondary vesicles )

Answer 7

1- Mesencephalon

2- Myelencephalon

Question 8

What are the structures of the Telencephalon

Answer 8

Cerebrum : cerebral hemispheres, cortex , white and grey matter

Question 9

What are the structures of the Diencephalon

Answer 9

Thalamus , Hypothalamus , epithalamus , retina

Question 10

What are the structures of the Mesencephalon

Answer 10

Brainstem : midbrain

Question 11

What are the structures of the Metencephalon

Answer 11

Brain stem : pons and Cerebellum

Question 12

What are the structures of the Myelencephalon

Answer 12

Brain stem : medulla oblongata

Question 13

By the 4th week the neural tube bends to produce what

Answer 13

1- Midbrain flexure ( ventrally ) between the prosencephalon and mesencephalon
2- Cervical flexure between hind brain and the spinal cord
3- Pontine flexure in the hindbrain

Question 14

What is the purpose of the brain flexures

Answer 14

So the brain can fit into the cranial cavity ( bends it )

Question 15

When does the pontine structure usually happen

Answer 15

5th week

Question 16

Explain the development of the ventricles

Answer 16

1- Dervied from dilation of the neural canal of the neural tube
2- Dilations in the prosencephalon lead to formation of lateral ventricles and third ventricle
3- Cavitation of the mesencephalon forms the cerebral aqueduct
4- Rhombencephalon dilation leads to formation of Fourth ventricle

Question 17

Where do the meninges arise from

Answer 17

Dura : mesoderm surrounding neural tube

Pia & arachnoid : neural crest cells

Question 18

Explain how the neural tube forms the neurones

Answer 18

cells in the wall of the neural tube ( ependymal ) give rise to neurones.
Divides into
1- Mantle layer : intermediate layer containing cell bodies of motor neuron ( grey matter)
2- Marginal layer : contains axons of motor neurons ( white matter )

Question 19

What are the divisions of the Mantle Layer

Answer 19

1- Alar Plate : dorsal sensory cell bodies receiving sensory axons form DRG
2- Basilar plate : ventral , cell bodies for motor neurones
3- Neuroepithelium gives rise to neuroblasts and glioblasts

Question 20

Cell bodies in Alar plate develop into

Answer 20

Dorsal gray columns , dorsal root of spinal nerves

Question 21

Cell bodies in Basal plate develop into

Answer 21

Ventral grey Columns, ventral root of spinal nerves

Question 22

Cell Bodie sin the roof plate develop into

Answer 22

Posterior median septum

Question 23

Cell bodies in the floor plate develop into

Answer 23

Ventral medial fissure

Question 24

Explain Neurogenesis proliferation

Answer 24

Process of neurones and glia proliferating , migrate and are specified to form mature brain

Proliferation :
1- Neuroepithelial cells lining neural tube differentiate into neuroblasts and glioblasts
2- Glioblasts form Oligodendrocytes and astrocytes
3- Neuroblasts form Neurones
4- Then after ependyma cells form the epithelium of the choroid plexus

Question 25

Explain Neurogenesis Migration

Answer 25

2 directions of migrations
1- Radial migration ( straight )
- Most cortical neurones migrate this way
- Occupy the deepest cortical layers , formed first
2- Tangental migration ( at angle )

2 different mechanisms of migration
1- somal translocation is self directed : nucleus of cell moves though cytoplasm and shortens axon
2- Glial mediated migration relies on radial glial cells
- Neurone wraps around glial cell and migrates along it

Question 26

Explain Neurogenesis Synpatogenesis

Answer 26

1- After elongation axons and dendrites make contacts and establish initial synapses
2- Synapses are constantly reconfigured in development and life
3- synaptic density in cortex in 1 to 2 years of age is at the highest , then stabilizes in adulthood