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NEUROANATOMY > (4) Development of CNS > Flashcards

(4) Development of CNS Flashcards

1
Q

when does the nervous system arise

A

3rd week of life

  • when 3 principal layers are being generated by process of gastrulation
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2
Q

what are the 3 principal layers of the nervous sytem

A

ectoderm

medoderm

endoderm

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3
Q

what happens during gastrulation?

A
  • outer cells (epiblast) of embryo detach, migrate through primitive streak (groove) –> mesoderm and ectoderm are generated
  • remaining outside cells (epiblast) form ectoderm, from which NS develops. Later becomes epidermis
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4
Q

what happens at the beginning of the 3rd week of development to the ectoderm layer

A

in response to signals from midline tissues (notochord and prechordal mesoderm)

the ectoderm layer begins to thick and form neural plate

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5
Q

what do the cells of the neural plate do? (2 things)

A
  • invaginate and form canal (basis of NS)

- make up neuroectoderm and their induction represents the initial event of neurulation

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6
Q

what is neurulation

A

formation of the nervous system

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7
Q

in which way does the NS mature?

A

top to bottom

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8
Q

the CNS begins initially from….

A

uniform sheet of cells= neuroepitheliu m

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9
Q

when is the neural plate formed and how

A

3rd week of development

  • longitudinal band of ectoderm thickens to form the plate
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10
Q

how is the neural groove formed

A

neural plate folds inwards forming neural groove, flanked by neural folds

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11
Q

how is neural tube formed

A

as neural groove deepens, the folds move medially and begin to fuse forming the neural tube

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12
Q

what is the function of notochord?

A

instruct NS to become ventral

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13
Q

what do somites give rise to

A

give rise to skeleton, skin, and specialized cells called melanocytes

– they are called dermomyotome

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14
Q

rostral vs caudal

A

rostral= top/upper

caudal= bottom/lower

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15
Q

cephalic and caudal ends of neural tube comminicate with…

A

until the fusion is complete, they communicate with amniotic cavity by way of cranial (anterior) and caudal (posterior) neuropores

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16
Q

what happens at day 25

A

closure of cranial neuropore

18-20 somites

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17
Q

what happens at day 27

A

closure of caudal neuropore

25 somites

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18
Q

close of neural tube sensitive to… (2)

A
  • environmental agents
  • aberrant gene activity

failure of proper closure leads to neural tube defects

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19
Q

neural tube separating from the ectoderm

A

as the tube closes (fusion occuring rostrally and caudally), it separates from overlying ectoderm

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20
Q

notochord involved in … and becomes

A

it is the transient axial mesodermal structure

  • involved in ventral patterning of NS
  • becomes incorporate in developing intervertebral disks of the skeleton
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21
Q

mesoderm-derived somites will form…

A

most of the vertebral column and segmental units of muscle (myotomes) and dermis (dermatome)

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22
Q

what happens at day 24 and 26

A

24: tube is closed at rostral end
26: closed at caudal end, local enlargements (primary vesicles) are apparent

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23
Q

3 primary vesicles

A

prosencephalon
mesencephalon
rhombencephalon

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24
Q

in early development, 2 types of tissues

A

epithelium (have basement membrane)

mesenchyme

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25
Q

what does the sulcus limitans do during closing of neural tube

A

separates dorsal and ventral tubes

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26
Q

neural tube defects frequency (live births)

A

occurs in 1 per 1000 live births

27
Q

3 types of neural tube defects

A

cranioarchischisis
anencephaly
spina bifida

28
Q

cranioarchischisis

A
  • open spinal cord and spine
  • CNS is abnormally open on dorsal surface
  • complete failure neural tube fusion
29
Q

anencephaly

A
  • failure rostral end of neural tube to close

- fetus born no/reduced head

30
Q

spina bifida

A
  • failure of caudal end of neural tube to close
  • caudal walls are continuous with skin of the back, the cord and meninges are displaced into a saclike cavity on back
  • vertebrate fail to form over lesion
  • can be corrected by surgery
31
Q

how does a primary vesicle form a secondary vesiscle

A

have specializations of primary vesicles to form secondary vesicles

32
Q

cephalic and cervical flexure

A
  • pockets of space

Cephalic= anterior, between mesencephalon and rhombencephalon
- secondary: between mesencephalon and metecephalon

Cervical= between rhombencephalon and spinal cord
- secondary: between myelencephalon and spinal cord

33
Q

prosencephalon secondary vesicles

A

prosencephalon= forebrain

  • Telencephalon
  • Diencephalon
34
Q

Derivative of telencephalon

A

cerebrum

35
Q

derivatives of diencephalon (4)

A

thalamus
hypothalamus
retina
other midbrain structures

36
Q

secondary vesicles of mesencephalon

A

(midbrain)

  • secondary vesicles= mesencephalon
37
Q

derivative of mesencephalon

A

midbrain

38
Q

rhombencephalon secondary vesicles

A

(hindbrain)

  • Metencephalon
  • Myelencephalon
39
Q

Metencephalon derivatives (2)

A

pons

cerebellum

40
Q

myelencephalon derivative

A

medulla

41
Q

list 5 secondary vesicles

A 
telencephalon 
diencephalon 
mesencephalon 
metencephalon 
myelencephalon
42
Q

fusion between diencephalon and telencephalon

A

part of cortical development

  • rapid expansion of cerebral hemispheres in 2nd month, results in downward folding of basal ganglia
  • by 3rd month, telencephalon and diencephalon have fused
43
Q

development of ventricular system

A

as each cerebral hemisphere grows in a C-shaped manner, so does its lateral ventricle

44
Q

flexures forming in ventricular system

A

as NS grows, spaces get trapped inside growing brai

and get different parts of ventricular system

  • ex: lateral ventricle, 3rd ventricle
45
Q

choroid plexus function

A
  • regulates fluid in ventricular system
  • continuation of blood supply in brain
  • initially start as blood vessels, then start making choroid plexus
46
Q

week 3 major developments (4)

A
  • neural groove and folds
  • 3 primary vesicles visible
  • cervical and cephalic flexures
  • motor neurons appear
47
Q

week 3 malformations

A

neural tube defects

48
Q

week 4 major developments (6)

A
  • neural tube starts to close (day 22)
  • rostral end of tube closes (day 24)
  • caudal end of tube closes (day 26)
  • neural crest cells begin to migrate
  • secondary neurulation starts
  • motor nerves emerge
49
Q

week 4 malformations (2)

A
  • neural tube defects

- holoprosencephaly

50
Q

week 5 major developments (8)

A
  • optic vesicle, pontine flexure
  • 5 secondary vesicles visible
  • sulcus limitans, sensory ganglia
  • sensory nerves grow into CNS
  • rhombic lips
  • basal ganglia begin
  • thalamus, hypothalamus begin
  • autonomic ganglia, lens, cochlea start
51
Q

week 5 malformations (2)

A

holoprosencephaly

sacral cord abnormalities

52
Q

week 6-7 major developments (6)

A
  • telencephalon enlarged
  • basal ganglia prominent
  • secondary neurulation complete
  • cerebellum and optic nerve begin
  • choroid plexus
  • insula
53
Q

week 8-12 major developments (5)

A
  • neural proliferation and migration
  • cerebral and cerebellar cortex begin
  • anterior commissure, optic chiasm
  • internal capsule
  • reflexes appear
54
Q

week 8-12 malformations

A

migration/proliferation problems

e.g. abnormal cortex/gyri

55
Q

week 12-16 major developments (3)

A
  • neuronal proliferation and migration
  • glial differentiation
  • corpus callosum
56
Q

week 12-16 malformations

A

migration/proliferation problems

e.g. abnormal cortex/gyri

57
Q

week 16-40 major developments (4)

A
  • neuronal migration
  • cortical sulci
  • glial proliferation, some myelination
  • synapse formation
58
Q

week 16-40 malformations

A
  • hemmorrhage

other destructive events

59
Q

neurocrest arises between

A

ectoderm and neuroectoderm

60
Q

neural crest cells

A

as neural tube separates from ectoderm, it leaves behind a group of cells that were at the crest of each neural fold

61
Q

where are cells born?

A

at the junction and migrate

62
Q

neural crest cells migrate and give rise to… (4)

A
  • sensory neurons (dorsal root ganglia of spinal nerves, some cranial nerves)
  • all post-ganglionic neurons of ANS
  • the adrenal medulla
  • Schwann cells
63
Q

major difference between cranial and trunk neural crest cells is…

A
  • cranial neural crest cells have ability to form cartilage and bone
64
Q

sulcus limitans divides…

A

developing neural tube into posterior alar plate

  • and anterior basal plate

that will give rise to sensory and motor areas of spinal cord and brainstem

NEUROANATOMY (7 decks)

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