Neural Development

Question 1

Describe how the neural tube develops

Answer 1

1. notochord (mesoderm) induces overlying ectoderm to differentiate into the neural plate
2. neural plate widens to form neural groove and folds (lateral edges)
3. neural folds join to form the neural tube (lumen - ventricular system and central canal)
4. dorsal cells differentiate into neural crest cells
5. somites (mesoderm) alongside the tube will later becomes muscle, vertebrae, and dermis

Question 2

anterior neuropore (what does it become, failure to close?)

Answer 2

becomes lamina terminalis; brain

leads to upper NTDs (anencephaly)

Question 3

posterior neuropore (what does it become, failure to close?)

Answer 3

becomes spinal cord
lower NTDs (spina bifida)

Question 4

neurocristopathy

Answer 4

malformation of neural crest cells

Question 5

schwannoma

Answer 5

• benign tumor of schwann cells
• encapsulated
• tinnitus, hearing loss
• frequently located near vestibular nerve

Question 6

neurofibromatosis type 1

Answer 6

• autosomal dominant
• mutation in NF1 gene => protein neurofibromin => downregulates p21 oncoprotein
• multiple neural tumors, skin lesions

Question 7

where do the optic vesicles arise from?

Answer 7

lateral extensions of diencephalon

• optic stalk connected to forebrain
• interaction with overlying ectoderm forms non-neural structures (lens, cornea)

Question 8

forebrain vesicles

Answer 8

prosencephalon
=> telencephalon
=> diencephalon

Question 9

midbrain vesicles

Answer 9

mesencephalon

=> mesencephalon

Question 10

hindbrain vesicles

Answer 10

rhombencephalon
=> metencephalon
=> myelenephalon

Question 11

telencephalon

Answer 11

regions
- cerebral cortex
- basal ganglia
- amygdala
- hippocampus
=> lateral ventricle

Question 12

diencephalon

Answer 12

Regions
-thalamus
-hypothalamus
-pituitary
-pineal
=> 3rd ventricle

Question 13

mesencephalon

Answer 13

Regions
- midbrain
=> cerebral aqueduct

Question 14

metencephalon

Answer 14

regions
- pons
-cerebellum
=> 4th ventricle

Question 15

myelencephalon

Answer 15

Regions - medulla

=> central canal

Question 16

alar plate

Answer 16

-sensory
-dorsolateral
-receives axons from DRG
=> dorsal horn

Question 17

functional components located in alar plate

Answer 17

GSA - sensory input
GVA - input from smooth muscles and glands
(SVA, SSA)

Question 18

basal plate

Answer 18

• ventrolateral

- projections motor neurons => ventral horn

Question 19

functional components of basal plate

Answer 19

GSE - motor output to skeletal muscles
GVE - autonomic control of smooth muscles and glnds
SVE

Question 20

sulcus limitans

Answer 20

longitudinal groove

extends from spinal cord to rostral midbrain

Question 21

caudal eminence

Answer 21

creates sacral and coccygeal segments of spinal cord

Question 22

when and where does myelination arise

Answer 22

• month 4 => 2 years of age (spinal cord) => 30 years (brain)
• arises in ventral roots

Question 23

spinal cord positions

Answer 23

conus medullaris:
- L3 at birth
- L1/L2 in adults
cauda equina - dorsal/ventral roots; below the conus medullaris
filum terminale - anchors spinal cord to coccyx

Question 24

development of the brainstem

Answer 24

1. canal expands to form 4th ventricle
2. alar plate is pushed lateral to basal plate
3. mesenchymal cells of the 4th ventricle attach to ependymal cells => pia mater

Question 25

development of the medulla

Answer 25

1. choroid plexus = off the roof
2. foramen of luschka (lateral)
3. foramen of magendie (median)
   pyramids (ventral)
4. STT/SCT

Question 26

spina bifida (meyloschisis) (general)

Answer 26

• vertebral arches fail to form
• lumbosacral more common
• folic acid

Question 27

spina bifida occluta

Answer 27

1. no neural tissue involved (sac is filled with CSF)
2. dimples, tufts of hair
3. least severe
4. spinous process does not form
5. spinal cord still intact

Question 28

spina bifida cystica

Answer 28

1. more severe
2. with meningocyele (meninges protrude, spinal cord intact)
3. with meningomyelocele (meninges and spinal cord protrude)

Question 29

spina bifida with rachischisis

Answer 29

• posterior neuropore doesn’t close (week 4)
• neural tissue becomes necrotic and fails to develop
• diagnosed by detected elevated alpha-fetoprotein

Question 30

cranium bifida (general)

Answer 30

• skull fails to form
• typically occipital plate
• folic acid

Question 31

cranium bifida with meningocele

Answer 31

• meninges protrude (sac of CSF)

Question 32

cranium bifida with meningoencephalocele

Answer 32

• meninges and brain tissue protrude

Question 33

cranium bifida with meningohydroencephalocele

Answer 33

• meninges, brain, ventricle protrude

Question 34

anencephaly

Answer 34

• severe upper NTD
• failure of brain to develop
• failure to thrive

Question 35

hydrocephalus/dandy-walker syndrome

Answer 35

• CSF accumulates in lateral ventricle (stenosis of cerebral aqueduct)
• failure of foramens Luschka and Magendie to form => enlarged 4th ventricle

Question 36

arnold-chiari malformation

Answer 36

caudal displacement of cerebellum through foramen magnum

• stretches cranial nerves 9-11
• difficulty swallowing
• spastic dysphonia
• diminished gag reflex
• apnea
• vocal cord paralysis

Question 37

microcephaly

Answer 37

• small cranial vault
• lack of brain development
• impaired mental