Development of the Nervous system

Question 1

soon after fertilisation - how many germ layers form?

Answer 1

3

Question 2

what are the three germ layers that form after fertilisation?

Answer 2

ectoderm (top)
mesoderm (middle)
endoderm (bottom)

Question 3

the three germ layers roll up into a tube - which layer is on the outside etc?

Answer 3

ectoderm (outside)
mesoderm (middle)
endoderm (inside)

Question 4

notochord forms from?

Answer 4

mesoderm cells soon after gastrulation is complete

Question 5

notochord induces overlying ectoderm to become?

Answer 5

neuroectoderm

Question 6

neuroectoderm will form?

Answer 6

the neural tube (CNS)
the neural crest (PNS)

Question 7

neuroectoderm thickens to form the?

Answer 7

the neural plate along dorsal longitudinal axis of embryo

Question 8

the neural groove?

Answer 8

a longitudinal trough appears

Question 9

what form the neural tube?

Answer 9

the sides of the neural plate rise up and seal over the top of the groove to form the neural tube

Question 10

what is primary neurulation?

Answer 10

closure of the neural tube
20 days in the canine foetus (out of 60d gestation)

Question 11

where does the neural tube start and extends to where?

Answer 11

in the cervical region and extends rostrally and caudally

Question 12

rostral and caudal neuropores?

Answer 12

when the ends of the neural tube possibly remains open for a period

Question 13

what does the neural tube surround?

Answer 13

the neural canal which is fluid-filled

Question 14

where does the neural tube extend?

Answer 14

extends the length of the embryo including into the head region

Question 15

what does the neural tube form?

Answer 15

forms the basis of the brain and spinal cord (i.e. central nervous system)

Question 16

what does the neural canal form?

Answer 16

the inner ventricular system

Question 17

what are the three cell layers that develop within the neural tube?

Answer 17

innermost germinal layer (cellular proliferation giving rise to neurones and other cells)
middle mantle layer
outer marginal layer

Question 18

where do neurones migrate to - if coming from germinal layer?

Answer 18

they migrate outward from germinal layer to surface (marginal layer) in cerebrum
to mantle layer in spinal cord

Question 19

why are grey and white matter reversed in brain and spinal cord?

Answer 19

because neurones migrate outward from germinal layer

Question 20

grey matter?

Answer 20

neurone cell bodies

Question 21

white matter?

Answer 21

myelinated neurone axons

Question 22

inside the head, what happens to the neural tube?

Answer 22

it expands and develops into three main regions

Question 23

what are the three main regions that the neural tube develops into?

Answer 23

the prosencephalon (forebrain)
the mesencephalon (midbrain)
the rhombencephalon (hindbrain)

Question 25

what does the hindbrain consist of?

Answer 25

metencephalon myelencephalon

Question 26

the diencephalon forms the?

Answer 26

the thalamus

Question 27

the forebrain develops as...

Answer 27

as two further regions: diencephalon and telencephalon (cerebrum)

Question 28

bilateral outgrowths of the ventral thalamus form the?

Answer 28

they form the optic cups which form the neurones of the retina and optic nerves

Question 29

what does the hindbrain also develop as?

Answer 29

as two further regions: metencephalon and myelencephalon

Question 30

metencephalon forms the?

Answer 30

the pons and cerebellum

Question 31

myelencephalon forms?

Answer 31

forms the medulla oblongata most caudal region of the brain, continuous with spinal cord

Question 32

what is the sulcus limitans?

Answer 32

a groove which forms in the lateral walls of the neural canal

Question 33

when do neural crest cells develop?

Answer 33

just before neural tube formation develop dorsolaterally at junction between neuroectoderm and ectoderm

Question 34

when do neural crest cells separate from the neuroectoderm and ectoderm?

Answer 34

at the same time as the tube develops

Question 35

columns of NCC from where?

Answer 35

along the dorsolateral aspects of the neural tube at the same time as the ectoderm fused over the neural tube to make overlying skin

Question 36

cells migrate from the neural crest columns - what does this give rise to?

Answer 36

to different cell populations around the body: melanocytes, noradrenaline-secreting cells of adrenal medulla, Schwann cells, post-synaptic cell bodies of autonomic ganglia

Question 37

what do the neural crest columns then fragment into?

Answer 37

into cell clusters

Question 38

where are the neural crest cell clusters located?

Answer 38

located bilaterally at each developing spinal cord segment

Question 39

what do the neural crest cell clusters become?

Answer 39

they become spinal ganglia i.e. clusters of neurone cell bodies associated with sensory nerves of the peripheral nervous system

Question 40

if cerebrospinal fluid (CSF) flow in the neural canal is blocked, what happens?

Answer 40

CSF accumulates and can result in hydrocephalus dilation of ventricular system pressure on surrounding brain tissue

Question 41

if the caudal neuropore fails to close, what can it result in?

Answer 41

abnormal spinal cord formation cystic dilation of meninges

Question 42

if the rostral neuropore fails to close, what happens?

Answer 42

forebrain development is compromised e.g. meninges can protrude through defect, causing meningocele e.g. failure of forebrain development (anencephaly)

Question 43

meningocele?

Answer 43

fluid fiuled dilation of meninges

Question 44

cerebellar hypoplasia

Question 45

teratogens (viruses, drugs) can cause?

Answer 45

abnormal development e.g. by destroying proliferating cells, resulting in hypoplasia

Question 46

malformations of the nervous system due to gene mutatuions?

Answer 46

e.g. in signalling proteins used by migrating cells