Nervous system development

Question 1

Notochord

Answer 1

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

Question 2

What is the “head region” organizer?

Answer 2

the prechordal plate

Question 3

What DOESNT the notochord stimulate formaiton of?

Answer 3

the anterior parts of the brain/head structure

Question 4

Primitive streak is replaced by the

Answer 4

notochord:

Question 5

how is the primitive streak replaced

Answer 5

migrating ectoderm cells from “median column”

cells move posterior to prechordal plate and become notochord

also called chordamesoderm

Question 6

The notochord stops growing just

Answer 6

inferiorly to the buccopharyngeal membrane

Question 7

Notochord is the primary inducer in what

Answer 7

early embryos

indcues overlying ectoderm to form neural plate —> neutral tube

Question 8

What does the notochord induce

Answer 8

overlying ectoderm (neural plate) to form neural tube

Question 9

What becomes of the notochord?

Answer 9

it will form part of intervertebral discs (nucleus pulpous)

Question 10

Induction of nervous system: 2 phases

Answer 10

Primary and Secondary neurulation

Question 11

Primary neurulation (time)

Answer 11

wks 3-4

Question 12

Secondary neurulation (time)

Answer 12

wks 5-6

Question 13

how does nervous induction occur in terms of signaling molecules?

Answer 13

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

Question 14

Blue box quote on neurulation: summarize in own words

Answer 14

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

Question 15

inhibition of BMP-4 = what during neurulation

Answer 15

neural formation

Question 16

Molecular regulation of neural induction

what molecules inhibit other molecules in terms of notochord signaling

Answer 16

Noggin, Chordin inhibit BMP-4 in overlying ectoderm

Wnt3a/FGF inhibit BMP-4 in overlying ectoderm

Question 17

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

Answer 17

the overlying ectoderm becomes SKIN instead of neural plate

Question 18

Cellular adhesion molecules involved in neural induction

Answer 18

CAMs. they keep cell clusters together

two big ones are E and N cadherin

they only bind to like cadherins

Question 19

E cadherin

Answer 19

epidermis formation

Question 20

N cadherion

Answer 20

neural plate formation

Question 21

What are the 4 stages of neural tube induction?

Answer 21

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

Question 22

what signaling molecule permeates the epidermis?

Answer 22

BMP4

Question 23

what does BMP4 induce after neural tube formation?

Answer 23

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

Question 24

Roof plate and Floor plate of neural tube

Answer 24

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

Question 25

neural tube concentration gradient

Answer 25

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

Question 26

what does the Shh/BMP-4 concentration gradient do

Answer 26

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

Question 27

Rachischisis

Answer 27

neural tube defects

Question 28

what happens when neuropores dont close

Answer 28

the cranial neuropore fails to develop, undeveloped brains are exposed

Question 29

anencephaly

Answer 29

neuropores fail to close, unviable life form

Question 30

Waves of neural tube closure

Answer 30

at least 5 waves of closure in normal embryogenesis

Question 31

anencephaly is failure of wave

Answer 31

2 of neural tube closure

Question 32

Spina bifida is wave

Answer 32

1 and 5 of neural tube non-closure

Question 33

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

Answer 33

normal spina bifida, caudal agenesis | shrunken in anencephaly

Question 34

Encephalocele

Answer 34

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

Question 35

Spina bifida occulta

Answer 35

vertebral column doesnt close, typified by a tuft of hair

Question 36

Spina bifida with meningomyelocele

Answer 36

large, skin covered bulge at posterior/lower lumbar spine. cavity is lined by meninges and spinal nerves herniate into cavity

Question 37

Meningomyelocele versus Meningocele

Answer 37

Meningomyelocele is a myelocele with meninges

Question 38

Prenatal surgery for spina bifida

Answer 38

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

Question 39

secondary neurulation

Answer 39

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

Question 40

associated malformations of secondary neurulation

Answer 40

myeldysplasias coccgyeal pits large superficial capillaries

Question 41

Tethered Cord Syndrome

Answer 41

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

Question 42

How does folic acid prevent neural tube defects?

Answer 42

.4 mg of folic acid decreases NT defects by 70%, mode of action poorly understood believed to be a homocysteine to methionine transformation

Question 43

NTDs: metabolic or dietary?

Answer 43

maybe both

Question 44

NTDs: what test will be elevated if present?

Answer 44

alpha fetoprotein AFP testing

Question 45

AFP

Answer 45

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

Question 46

AFP elevatation can be tested in

Answer 46

can be tested in maternal blood

Question 47

AFP is produced in the

Answer 47

fetal liver

Question 48

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. ```

Answer 48

all CNS by neural tube, all PNS by neural crest

Question 49

Albinism

Answer 49

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

Question 50

Vitiligo

Answer 50

loss of melanocytes autoimmune disorder can be reversed

Question 51

ED syndrome

Answer 51

ectoderm dysplasia syndrom

Question 52

EDS

Answer 52

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

Question 53

Epithelial ectoderm --->

Answer 53

oil

Question 54

Lateral mesoderm --->

Answer 54

appendicular skeleton

Question 55

endoderm --->

Answer 55

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