CNS Development

Question 1

what week does development of the brain begin?

Answer 1

3rd week post-conception and continues into early adulthood

Question 2

what do genes determine?

Answer 2

correct sequence and evolution with neuronal proliferation, migration and reorganisation
development of dendritic and axonal interconnections
development of synapses, receptors and neurotransmitters

Question 3

two types of environments that influence brain development

Answer 3

intrauterine

extrauterine

Question 4

how does the intrauterine environment affect brain development?

Answer 4

maternal heath and disease (maternal PKU risks crossing placenta and affecting the brain)
insults that are continuous or episodic during pregnancy e.g. alcohol or CMV
placental nutrition (delivery failure risks intrauterine growth retardation)

Question 5

how does the extrauterine environment affect brain development

Answer 5

• physical factors e.g. nutrition and environmental toxin
• emotion and social factors e.g. neglect and lack of stimulation
• exposure to drugs, alcohol and other related substances

Question 6

four stages to brain development

Answer 6

embryonic
foetal development
post-natal development
adolescent brain

Question 7

time frame of embryonic brain development

Answer 7

conception to week 9

Question 8

how does gastrulation and the three layered embryo formed?

Answer 8

the two layered embryo consists of epiblasts and hypoblasts between which the primitive streak/node has cells migrate through (route of migration is determined by nodal signalling)

Question 9

three layers of the embryo

Answer 9

ectoderm= skin, nails, hair and neural tissue
mesoderm= muscle, bone, cartilage and vascular system
endoderm= gut and respiratory system

Question 10

what days does the neural tube form

Answer 10

day 20-27

Question 11

describe the formation of the neural tube

Answer 11

neural progenitor cells form neural plate which develops a groove and folds into a tube. the progenitor cells line the tube (ventricular zone). hollow centre becomes the ventricular system and central channel of the spinal cord

Question 12

what does the rostral tube become?

Answer 12

brain

Question 13

what does the caudal tube become?

Answer 13

spinal cord

Question 14

signalling molecules

Answer 14

Pax6

Emx2

Question 15

what does high concentration of Pax6 and low concentration of Emx2 cause

Answer 15

progenitors become motor neurone in the anterior and rostral area

Question 16

what does low Pax6 and high Emx2 induce?

Answer 16

visual cortical neurones (posterior/caudal)

Question 17

how does the appearance of the brain change in foetal development?

Answer 17

brain is initially lissencephalic and gradually develops a folded appearance (sulcal and gyro pattern- accommodates more neurones)

Question 18

formation of three sulci

Answer 18

primary= week 8-26
seconday= 30-35
teritary= 36 to early infancy

Question 19

describe brain development in foetal stage of CNS development

Answer 19

• neuronal progenitor cells in the VZ divide to form two identical progenitor cells (days 25-42)
• asymmetrical division follows producing one progenitor cell and one neurone (post-mitotic, loss cannot be re-established)
• migrate to developmental neocortex

Question 20

two main processes in post-natal development

Answer 20

1. proliferation and migration= limited in VZ but does happen elsewhere
2. myelination

Question 21

describe the process of myelination in post-natal development

Answer 21

oligodendrocytes progenitor cells wraps around axons (myelin sheaths)

Question 22

what does myelination cause?

Answer 22

increased conduction rate
axon integrity
diameter
survival

Question 23

direction of myelination formation

Answer 23

bottom to top

back to front

Question 24

what input is needed post-natally

Answer 24

environmentally diverse and experiences

Question 25

what happens during adolescent brain development?

Answer 25

reorganisation of the brain with many synapses eliminated, increase in white volume and change in neurotransmitter system

Question 26

what does monocular visual deprivation cause in later life

Answer 26

altered organisation of primary visual cortex as both eyes develop dominance columns, if one eyes becomes blocked the band shrinks and the active eye invades this territory

Question 27

what do insults during neural tube formation lead to?

Answer 27

anencephaly | spina bifida

Question 28

insults during development of brain vesicles

Answer 28

holoprosencephaly

Question 29

disorders of myelination

Answer 29

hypermyelination dysmyelination demyelination (formed then lost)

Question 30

what does the PLP1 gene code for?

Answer 30

myelin protein present in CNS

Question 31

what is myelin protein responsible for?

Answer 31

compaction, stabilisation and maintenance of myelin sheaths oligodendrocyte development axonal survival

Question 32

where is the PLP1 gene located?

Answer 32

X chromosome (boys)

Question 33

most severe form of mutation in PLP1 gene

Answer 33

Pelizaeus-Merzbacher

Question 34

presentation of PLP1 gene mutation

Answer 34

``` infancy/early childhood nystagmus hypotonia cognitive impairment progresses to severe spasticity and ataxia life span shortened ```

Question 35

impact of malnutrition

Answer 35

brain growth and volume myelination energy and deprivation (experience and stimulation) disease and debilitation