Basics Of Brain Development

Question 1

What CNS cells arise from the ectoderm?

Answer 1

Neurons
Astrocytes
Oligodendrocytes

Question 2

What CNS cells arise from the mesoderm?

Answer 2

Microglia

Question 3

When does the cortical plate begin to form?

Answer 3

Around 8 weeks post conception

Question 4

What is the totipotence?

Answer 4

The potential of a cell to create a full being

Question 5

At what stage do the germ layers arise?

Answer 5

Gastrulation

Question 6

What are the three germ layers?

Answer 6

Ectoderm
Mesoderm
Endoderm

Question 7

What is the fate of ectoderm?

Answer 7

Skin or CNS

Question 8

When does the gastrulation stage take place?

Answer 8

E13 (3 weeks post conception)

Question 9

Where is the Spemann organiser and what does it do?

Answer 9

In the mesoderm
Involved in induction - changes the fate of cells

Question 10

What side of the ectoderm becomes skin?

Answer 10

Ventral

Question 11

What side of the ectoderm becomes brain? (Think of an animal lying prone)

Answer 11

Dorsal

Question 12

What morphogen induces ectoderm to become skin?

Answer 12

BMP-4

Question 13

How does the Spemann organiser induce ectoderm to become the neural plate?

Answer 13

Releases morphogens (chordin, noggin) to dorsal ectoderm
These prevent binding to BMP-4
Ectoderm take the default path and become the neural plate

Question 14

What is the role of sonic hedgehog?

Answer 14

Cells into the brain areas according to gradient
(Telencephalon to hindbrain)

Question 15

What condition occurs from a homozygous mutation in Sonic hedgehog?

Answer 15

Holoprosencephaly (Cyclopia)

Question 16

What brain areas are microglia involved in the formation of?

Answer 16

Cerebellum
Corpus callosum

Question 17

When do microglia move into the brain?

Answer 17

4 post conceptional weeks

Move from the yolk sac into the brain through the blood supply

Question 18

What is the role of CSF1R?

Answer 18

Signals the microglia to move into the brain

Without this: cerebellar and callosal agenesis

Question 19

What are the three subdivisions that form from the neural tube?

Answer 19

Forebrain - prosencephalon
Midbrain - mesencephalon
Hindbrain - rhombencephalon

Question 20

What does the forebrain a
Divide into?

Answer 20

Telencephalon - cortex
Diencephalon - subcortical structures (basal ganglia, thalamus)

Question 21

What does the rhombencephalon (hindbrain) divide into?

Answer 21

Pons
Cerebellum
Medulla

Question 22

What conditions arise from the neuropores at the neural tube not closing?

Answer 22

Anencephaly - rostral pore
Spina bifida - caudal pore

Question 23

How can neural tube defects be prevented?

Answer 23

Folic acid supplements

Question 24

When does the neural tube close?

Answer 24

Between 21 and 28 days

Question 25

What does the notch pathway do?

Answer 25

Inhibits proneural genes in a subset of progenitor cells Progenitor cells become glial cells instead of neurons

Question 26

Where do excitatory neurons arise from?

Answer 26

Ventricular zone Migrate towards the cortical (pial) surface

Question 27

Where do inhibitory neurons arise from?

Answer 27

Ganglionic eminence Migrate tangentially to pial surface

Question 28

What are the earliest born neurons in the cortex?

Answer 28

Layer 6 Deepest layer Neurons arise from the deep to the surface

Question 29

What gene mutation causes schizencephaly?

Answer 29

EMX2 Disorder of proliferation and onset of migration

Question 30

What genetic mutation causes lissencephaly?

Answer 30

LIS1 DCX Disorder of ongoing migration

Question 31

What genetic mutation causes lissencephaly type 2?

Answer 31

FCMD Disorder of arrest of migration

Question 32

What does mutation in reelin affect?

Answer 32

Layering of cortex

Question 33

How does the number of dendritic spines/synapses differ in Alzheimer’s?

Answer 33

Numbers reduce in line with the time of onset

Question 34

How does the number of dendritic spines/synapses differ in Autism?

Answer 34

Formation is higher in childhood Elimination is lower throughout life

Question 35

How does the number of dendritic spines/synapses differ in Schizophrenia?

Answer 35

Elimination is higher than in normal controls Timing is in line with onset of disorder

Question 36

What are the facial features of feral alcohol syndrome?

Answer 36

Small eye openings Smooth philtrum Thin upper lip