Neuroembryology

Question 1

What does the notochord help develop?

Answer 1

The spinal cord and spinal nerves via signaling molecules

Turns the caudal/inferior neuroectoderm physically into these structures

Question 2

What does the prechordal mesoderm help produce?

Answer 2

Brain and cranial nerve development via signal molecules

The rostral/superior neruoectoderm turns physically into the Brain and cranial nerves

Question 3

What is the process of neural induction/Neurulation mainly give rise to?

Answer 3

Differentiates the ectoderm into the neuroectoderm (neural plate)
- neuroectoderm eventually turns into Brain/spinal cord

Also gives rise to neural tube and neural crest cells

Question 4

What does surface ectoderm (ectoderm that does differentiate into neuroectoderm) give rise to ultimately?

Answer 4

The skin

Question 5

What are the signaling molecules secreted ventrally in the neural tube?

Answer 5

SHH

RA

Noggin

Chordin

are all secreted from the ventral floor plate

Question 6

What are the signaling molecules secreted dorsally in the neural tube?

Answer 6

TDF-B

BMPs

Dorsalin

RA

Noggin

all are secreted from the dorsal roof plate

Question 7

What are the signaling molecules secreted lateral to the neural tube ?

Answer 7

BMPs

these are secreted form the somites

Question 8

Dysraphisms

Answer 8

Various neural tube defects (NTDs)
- usually in formation and fusion of the neural tube

Usually occur at or near anterior/posterior neuropores

Highly linked to low maternal folate/B9 levels in conception and early pregnancy

Most heavily associated defects include cranium or spinal bifida

Question 9

Different types of cranial bifida

Answer 9

Meningocele
- contents include just CSF and meninges

Meningoencephalocele
- contents include CSF, brain tissue and meninges

Meningohydroencephalocele

• contents include CSF, Brian tissue, ventricles and meninges
• most severe

Question 10

Different types of spina bifida

Answer 10

Spina bifida occulta

• unfixed neural arch that does NOT produce a cyst
• asymptomatic except sometimes tuffs of dark hair form in the area

Spina bifida cystic w/ meningocele
- cyst forms and includes meningitis and CSF only

Spina bifida cystic w/ meningomyelocele
- cyst forms and includes meningitis, CSF, Brain matter and spinal cord tissues

Question 11

Myeloschisis

Answer 11

Posterior neurochord does not close

Leaves open spinal cord exposed.

Not compatable with life

Question 12

Meroencephaly

Answer 12

Anterior neurochord does not close

Causes exposed Brain

Does not affect and bones

Question 13

What do the neural crest cells give rise to?

Answer 13

All glial cells of the PNS

Most of the PNS nerves and ganglia

Question 14

Where are the primary sensory neurons for CN 1 and 2 located?

Answer 14

CN1 = olfactory epithelium fund in the nasal cavity

CN2 = retina of the eye

both do NOT originate from neural crest cells

Question 15

What do sensory ganglia of the true cranial nerves originate from?

Answer 15

Either cranial neural crest cells of neurogenic placodes (thickened surface ectoderm)

Question 16

Sympathetic ganglia of PNS develop from what?

Answer 16

All arise from trunk crest neural crest cells

Question 17

Parasympathetic ganglia of the PNS arise from what?

Answer 17

Postganglionic arise from neural crest cells

Question 18

Parasympathetic ganglion and their associated Cranial nerve

Answer 18

Ciliary ganglion = CN 3

Pterygopalatine ganglion = CN 7

Submandibular ganglion = CN 7

Otic ganglion = CN 9

intramural ganglia = CN 10

Enteric ganglia = CN 10

Question 19

What do apolar neuroblast cells give rise to?

Answer 19

All types of neurons in the body

• bipolar
• unipolar
• multipolar
• pseudounipolar

are derived from neuro-epithelium/ neuroectoderm

Question 20

What do gllioblast cells give rise to?

Answer 20

All the glial cells in the CNS

• radial glial cells
• astrocytes
• oligodendrocytes
• are derived from neuroepothelium/ neuroectoderm*

Question 21

What are the 1 group of glial cells that are NOT derived from neuroectoderm?

Answer 21

Microglia

- derived from monocytes/ bone marrow

Question 22

How does the neural tube differentiate?

Answer 22

1) The original single layer of ectoderm gives rise to the ventricular zone
- contains the original precursors/ progenitor neuroblast/glialblasts that eventual move into ventricular zone

This layer elongates and forms a new layer called the marginal zone

• contains only neuro blasts and glialblasts projections. NO nuclei
• eventually, gives rise to all of the white matter

The last layer to develop is the intermediate zone (mantle zone)

• contains neuroblast and glioblasts that migrate from the ventricular zone
• eventually gives rise to all of the gray matter over time

Question 23

Steps for differentiation of the intermediate zone

Answer 23

caused by gradient of signaling molecules

Alar plate (column) 
- house all dorsal neuroblasts that inevitably turn into all 2nd and 3rd sensory (both visceral and somatic) neurons and associated interneurons 

Basal plate (column) 
- houses all ventral neuroblasts that inevitably turn into all lower motor neurons (somatic motor and presynaptic autonomic) and associated interneurons

• these plates are separated by the sulcus limitans (also called central canal in spinal cord)*

Question 24

How are the motor and sensory columns aligned in both the alar and basal plate?

Answer 24

Basal plate
- ventral part = houses cell bodies of the somatic motor neurons (somatic efferent motor columns)

• dorsal part = houses presynaptic cell bodies for visceral motor neurons (visceral efferent motor columns)

Alar plate
- ventral part = houses cell bodies for visceral afferent/sensory neurons (visceral afferent sensory columns)

• dorsal part = houses cell bodies for somatic afferent/sensory neurons (somatic afferent sensory columns)

Question 25

What do lower moter neurons do?

Answer 25

They are somatic motor neurons. They innervate skeletal muscles

Question 26

Basal plate derivatives specifics

Answer 26

Medial motor column of the basal plate (MMC) - controls somatic motor neurons that innervate the skeletal muscles of the trunk and limb girdles - also called “anterior horn” Lateral motor column of the basal plate (LMS) - controls somatic motor neurons that innervate the skeletal muscles of the upper and lower limbs - exception is accessory nerve bodies (these are found in the spinal accessory nucleus) Intermediolateral (IML) nucleus of the basal plate - controls presynaptic sympathetic visceral motor neurons within the T1-L2 Region - controls presynaptic parasympathetic visceral motor neurons within the S2-4 region - also known as “lateral horn”

Question 27

Alar plate derivatives specifics

Answer 27

Dorsal region of the dorsal horns = secondary somatic afferent neurons and runs along the entire spinal cord length Deeper regions of the dorsal horns = secondary visceral afferent neurons and runs only in the T1-L2 region and S2-4 region

Question 28

Marginal zone of the mature spinal cord and the general concept of tract layouts

Answer 28

* note that the marginal zone contains the white matter, not gray* 1) sensory information from the trunk/limbs/viscera are carried up to the brain by ASCENDING axon fibers from all secondary afferent and some primary afferent neurons 2) signals from the brain to activate or inhibit firing of targeted lower motor neurons travel down spinal cord DESCENDING axon fibers 3) due to fibers of each pathway often decussing to the contralateral side, lesions that occur prior to decussations show signs/symptoms on contralateral side. Lesions after decussations show sings/symptoms on the ipsilateral side.

Question 29

Teathered spinal cord

Answer 29

Abnormal attachment of the spinal cord to vertebra or surrounding tissues during growth and elongation - stretches it to far and it goes past L2. Causes unwanted tension on spinal cord and nerves Symptoms/signs - often accompanies NTDs - pain in back/lower extremities - numbest of lower extremities - muscular weakness of lower extremities/ back - bowel and bladder issues

Question 30

Development of the brain

Answer 30

Rostral/superior portion of the neural tube forms three swellings Prosencephalon (forebrain) - splits into telencephalon and diencephalon by the pontine flexure Mesencephalon (midbrain) Rhombencephalon (hindbrain) - splits into mesencephalon and myelencephalon by pontine flexure *once the 5 parts are split, the basal plate becomes medial to the alar plate (rotates clockwise 90 degrees due to cephalic and cervical flexures )*

Question 31

Myelencephalon and its basal plate associated derivatives

Answer 31

Forms the medulla oblongata Basal plate derivatives associated: - somatic efferent column (most medial) = somatic motor nucleus of CN12 - visceral efferent motor column (most lateral) = pre-synaptic parasympathetics for salivary nucleus of CN12 and dorsal motor nuclei of CN10 - special visceral/branchial efferent column = nucleus ambiguous which contains efferent motor neurons of CN10

Question 32

Myelencephalon and its Alar plate associated derivatives

Answer 32

Visceral afferent (sensory) column = gives rise to secondary sensory neurons of solitary nucleus (taste and abdominal visceral for CN10). Also does carotid body and sinus visceral afferents (CN9/10) Somatic afferent (sensory) column = gives rise to secondary sensory nuceli of CN5 Special somatic afferent column =gives rise to secondary sensory neurons to form vestibular and cochlear nuceli (CN8) * also generates curate/gracile nuclei/ inferior Olivary nuclei