Nervous System Development

Front 1

What is the primordium of the nervous system & from what germ layer is it derived?

Back 1

Primordium = Neural tube

Derived from Ectoderm

Front 2

What is neurulation?

Back 2

Formation of the neural tube - in two phases (primary/secondry)

Front 3

When does Primary neurulation occur?

Back 3

End of week 3 to early week 4

Front 4

What begins Primary neurulation?

Back 4

Formation of neural plate

Front 5

What is the Neural Plate?

Back 5

Thickened area in center of ectoderm cranial to primitive node.

Front 6

What causes the neural plate to form?

Back 6

Interaction between Notochord and Overlying Ectoderm

Front 7

What is the name of neural plate adjacent to notochord?

Back 7

Floor Plate

Front 8

What happens to the Floor Plate?

Back 8

Cellular changes occur so it acts as Median hinge point

Front 9

What results from forming a Median Hinge Point?

Back 9

Bending of the neural plate so a midline Neural Groove forms, w/ Neural Folds on either side.

Front 10

What happens to the neural Folds?

Back 10

They Fuse and form the neural tube

Front 11

But what happens just before the neural folds fuse?

Back 11

Neural Crest cells separate by epithelial-mesenchymal transformation.

Front 12

What happens to the ends of the neural tube?

Back 12

They stay open for a while to ensure flow of amniotic fluid til vessels develop

Front 13

What kind of tissue is
-Neural tube
-Neural crest

Back 13

Tube = epithelium

Crest = mesenchyme

Front 14

What does the Neural Tube NT become?

Back 14

-Brain
-Spinal cord

Front 15

What does the lumen of the NT become?

Back 15

The ventricles of the brain

Front 16

What portion of the CNS is formed by:
-Primary neurulation?
-Secondary neurulation?

Back 16

Primary = Brain thru S2

Secondry = S3 thru Coccyx

Front 17

Where does 2ndary neurulation begin?

Back 17

At the Caudal eminence

Front 18

What tissue participates in 2ndary neurulation? What does it form?

Back 18

Undifferentiated mesenchyme - becomes the Neural CORD.

Front 19

How does the neural Cord associate with the Tube?

Back 19

The Cord grows toward the tube and they become continuous.

Front 20

What is essential for complete CNS formation?

Back 20

BOTH primary and secondary neurulation.

Front 21

Disease caused by Error in 2ndary neurulation:

Back 21

Myelodysplasia

Front 22

Symptom of Myelodysplasia:

Back 22

Pigmented skin covers defect

Front 23

2 alternate names for errors of primary neurulation:

Back 23

Dysraphic errors
Neural tube Defects

Front 24

Where are Dysraphic/neural tube defects located? Why?

Back 24

Midline and Dorsal b/c they are caused by Faulty closure of neural folds.

Front 25

Where do Dysraphic defects usually occur?

Back 25

At neuropores

Front 26

What supplement affords some protection against neural tube defects?

Back 26

Folic acid supplements

Front 27

What % of Fetal vs. Infant deaths caused by congenital conditions are from nervous system defects?

Back 27

Fetal: 75%

Infant: 40%

Front 28

What % of all malformations in develpmnt are due to nervous system defects?

Back 28

10%

Front 29

What % of embryos affected by nervous system defects are lost during week 4-8?

Back 29

90%

Front 30

4 Neural Tube defects involving BRAIN:

Back 30

-MeroAnencephaly
-Meningoencephalocele
-Cranial Meningocele
-Cranium Bifidium

Front 31

What is Meroanencephaly?

Back 31

Absence of the Calvaria
Rudimentary mass instead of brain
Only brainstem

Front 32

How is meroanencephaly diagnosed?

Back 32

-Ultrasound
-Incr alpha fetoprotein levels

Front 33

What are the common characteristics of Meningoencephalocele?

Back 33

-Bifid Cranium skull defect
-Herniated Brain/Meningies
-Hydrocephaly, polydactyly, polycystic kidney

Front 34

What are the 2 deficits associated with meningoencephalocele?

Back 34

-Quadraplegic
-Incontinence

Front 35

What is Cranial Meningocele?

Back 35

A small defect in the skull
-No brain herniation
-Just herniated meningeal sac filled w/ CSF

Front 36

What is Cranium bifidium?

Back 36

An opening between the skull bones
-Usually asymptomatic

Front 37

What is the collective name for Neural tube defects involving the spinal cord?

Back 37

Spina bifida

Front 38

What does Aperta mean?

Back 38

Open

Front 39

Who do we see more of each in?
-Meroanencephaly
-Spina bifida

Back 39

Meroanenceph = Females 3:1

Spina bifida = Males

Front 40

What is Myeloschisis?

Back 40

Vertebral defect - neural arches are unfused so the neural plate is open dorsally

Front 41

How common is myeloschisis?

Back 41

Not at all - very rare

Front 42

What are the majority of spina bifida cases?

Back 42

Meningomyelocele - 90%

Front 43

What are the characteristics of Meningomyelocele?

Back 43

-Verebral defect
-Cystic swelling that can be covered with skin or membrane
-Herniated spinal cord and meninges

Front 44

What defects are associated with meningomyelocele?

Back 44

-Club foot
-Hydrocephalus

Front 45

What deficits are associated with meningomyelocele?

Back 45

-Urinary incontinence
-Paraplegia

Front 46

What is the 2nd most common spina bifida? What %?
How is it different from Meningomyelocele?

Back 46

Meningocele - 10% of cases
-Only meningeal herniated (not spinal cord)

Front 47

What is meningocele characterized by?

Back 47

-Vertebral defect
-Herniated meningeal sac filled w/ CSF

Front 48

What term classifies both Meningocele or Meningomyelocele?

Back 48

Spina Bifida Cystica

Front 49

What is Spina Bifida Occulta?

Back 49

A vertebral defect limited to 1/2 vertebral levels and often asymptomatic

Front 50

What percent of population has spina bifida occulta?

Back 50

10%

Front 51

What is Diastematomyelia?

Back 51

A bone spur in spinal canal associated w/ hair tuft/dimple - can tether spinal cord and prevent normal ascension in spinal canal.