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MSK I > Nervous system development > Flashcards

Nervous system development Flashcards

1
Q

Notochord

A

major axial signaling center of the trunk: does not stimulation formation of anterior parts of the brain or head

head region is organized by prechordal plate

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2
Q

What is the “head region” organizer?

A

the prechordal plate

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3
Q

What DOESNT the notochord stimulate formaiton of?

A

the anterior parts of the brain/head structure

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4
Q

Primitive streak is replaced by the

A

notochord:

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5
Q

how is the primitive streak replaced

A

migrating ectoderm cells from “median column”

cells move posterior to prechordal plate and become notochord

also called chordamesoderm

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6
Q

The notochord stops growing just

A

inferiorly to the buccopharyngeal membrane

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7
Q

Notochord is the primary inducer in what

A

early embryos

indcues overlying ectoderm to form neural plate —> neutral tube

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8
Q

What does the notochord induce

A

overlying ectoderm (neural plate) to form neural tube

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9
Q

What becomes of the notochord?

A

it will form part of intervertebral discs (nucleus pulpous)

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10
Q

Induction of nervous system: 2 phases

A

Primary and Secondary neurulation

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11
Q

Primary neurulation (time)

A

wks 3-4

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12
Q

Secondary neurulation (time)

A

wks 5-6

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13
Q

how does nervous induction occur in terms of signaling molecules?

A

probably secrete inhibitory signals that obstruct other inhibitory signals, allowing the overlying ectoderm to differentiate into neural tissue as a default state

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14
Q

Blue box quote on neurulation: summarize in own words

A

signaling molecules from notochord dont act directly on ectoderm but inhibit other factors like BMP-4.

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15
Q

inhibition of BMP-4 = what during neurulation

A

neural formation

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16
Q

Molecular regulation of neural induction

what molecules inhibit other molecules in terms of notochord signaling

A

Noggin, Chordin inhibit BMP-4 in overlying ectoderm

Wnt3a/FGF inhibit BMP-4 in overlying ectoderm

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17
Q

What happens if BMP-4 isn’t blocked during neurulation?

A

the overlying ectoderm becomes SKIN instead of neural plate

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18
Q

Cellular adhesion molecules involved in neural induction

A

CAMs. they keep cell clusters together

two big ones are E and N cadherin

they only bind to like cadherins

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19
Q

E cadherin

A

epidermis formation

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20
Q

N cadherion

A

neural plate formation

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21
Q

What are the 4 stages of neural tube induction?

A

1) neural plate induction
2) neural fold and neural groove induction
3) contractile fibers in neuralepithelia pull folds together
4) fusion of neural plate to form neural tube

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22
Q

what signaling molecule permeates the epidermis?

A

BMP4

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23
Q

what does BMP4 induce after neural tube formation?

A

induces a new signaling center in the roof plate, which also secretes BMP-4

24
Q

Roof plate and Floor plate of neural tube

A

overlying epiderm secretes BMP4 which induces roof plate to become a signaling center (also secreting BMP4)

underlying notochord signals floor plate with Shh to become a signaling center, which will also secrete Shh

25
Q

neural tube concentration gradient

A

dorsally = double BMP-4 gradient from epiderm and roof plate

ventrally = Shh gradient from floor plate

26
Q

what does the Shh/BMP-4 concentration gradient do

A

it specifies the identity of the neurons in the tube by reading the concentration of the two factors

creates an AP-Dorsal/Ventral coordinate system along which cells can be parceled into unique fates

along the longitudinal axis: specifies Hox gene expression

27
Q

Rachischisis

A

neural tube defects

28
Q

what happens when neuropores dont close

A

the cranial neuropore fails to develop, undeveloped brains are exposed

29
Q

anencephaly

A

neuropores fail to close, unviable life form

30
Q

Waves of neural tube closure

A

at least 5 waves of closure in normal embryogenesis

31
Q

anencephaly is failure of wave

A

2 of neural tube closure

32
Q

Spina bifida is wave

A

1 and 5 of neural tube non-closure

33
Q

what kind of cranial structure would we see in spina bifida versus ancencephaly?

A

normal spina bifida, caudal agenesis

shrunken in anencephaly

34
Q

Encephalocele

A

failure of wave junctions at 4/1

cranial defect with herniation of intracranial content, most common in occipital region

cariants can contain meninges, brain, and ventricular system

produces a meningoencephalocele

35
Q

Spina bifida occulta

A

vertebral column doesnt close, typified by a tuft of hair

36
Q

Spina bifida with meningomyelocele

A

large, skin covered bulge at posterior/lower lumbar spine.

cavity is lined by meninges and spinal nerves herniate into cavity

37
Q

Meningomyelocele versus Meningocele

A

Meningomyelocele is a myelocele with meninges

38
Q

Prenatal surgery for spina bifida

A

most of the damage occurs late in pregnancy

spina bifida sac allows amniotic fluid in to the hold of the spin, damaging developing spinal cord = life long paralysis

39
Q

secondary neurulation

A

caudal to posterior neuropore: remaining neural tube is formed by secondary neurulation

40
Q

associated malformations of secondary neurulation

A

myeldysplasias

coccgyeal pits
large superficial capillaries

41
Q

Tethered Cord Syndrome

A

conus medullaris and filum terminale are abnormally attached to the defective vertebral column

constant traction damages the spinal cord

can lead to subsequent loss of sensation from the lower limbs and problems with bladder control

42
Q

How does folic acid prevent neural tube defects?

A

.4 mg of folic acid decreases NT defects by 70%, mode of action poorly understood

believed to be a homocysteine to methionine transformation

43
Q

NTDs: metabolic or dietary?

A

maybe both

44
Q

NTDs: what test will be elevated if present?

A

alpha fetoprotein AFP testing

45
Q

AFP

A

alpha fetal protein
produced in the liver. in fetus with open NTD, AFP leaks across the defect into the amniotic fluid across placenta and into maternal serum

46
Q

AFP elevatation can be tested in

A

can be tested in maternal blood

47
Q

AFP is produced in the

A

fetal liver

48
Q

Derivatives of neural ectoderm

which develops from the neural tube and which develops from neural crest?

sensory ganglia and PNS 
eyes
teeth
skin 
CNS
PINEAL body
posterior pit.
A

all CNS by neural tube, all PNS by neural crest

49
Q

Albinism

A

autosomal recessive, global reduction or absence of pigment in skin, hair eyes

50
Q

Vitiligo

A

loss of melanocytes
autoimmune disorder
can be reversed

51
Q

ED syndrome

A

ectoderm dysplasia syndrom

52
Q

EDS

A

sparse hair, malformed teeth. requires at least TWO identifications (so teeth and hair would be two in this case)

effects both men and women

53
Q

Epithelial ectoderm —>

A

oil

54
Q

Lateral mesoderm —>

A

appendicular skeleton

55
Q

endoderm —>

A

lining of urogenital track, vascular system, guts, liver, pancreas etc

MSK I (14 decks)

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