Embryology of the Nervous System

Question 1

When does most neuronal production and migration occur?

Answer 1

•third through fifth months of development•

The formation of neural connections (neuropil) and production of myelin sheaths continue after birth

Question 2

When does gliogenesis take place?

Answer 2

during the second and third trimesters of pregnancy and early postnatal development

Question 3

What does the mesoderm provide to the ectoderm

Answer 3

neural-inducing morphogens

Question 4

what is required for formation of the neural plate?

What does the plate come from

Answer 4

Notochord

overlying ectoderm

Question 5

What is neurulation?

What does it involve?

Answer 5

process of forming the neural tube from ectoderm

•Neurulation involves:
–1) Formation of a neural plate
–2) Neural plate becomes neural groove surrounded by crests
–3) Groove becomes closed neural tube in highly ordered fashion

Question 6

What does spina bifida result from?

Answer 6

Incomplete caudal neural tube closure

Question 7

What does anencephaly result from?

What is something that may prevent this?

Answer 7

Incomplete rostral neural tube closure.

Folate?

Question 8

What does the neural tube develop into?

Answer 8

CNS

Question 9

What are the3 vesicles that develop into the future brain?

Answer 9

Prosencephalon of forebrain

Mesencephalon of midbrain

Rhombencephalon of hindbrain

Question 10

What are the flexures composed of, (structures)

What are the 5 secondary vesicles after seperation?

Answer 10

1. –Cephalic flexure bet. Mesencephalon and prosencephalon
2. –Cervical flexure bet. Rhombencephalon and spinal cord
3. –Rhombencephalon sep. to metencephalon and myelencephalon at level of pontine flexure
4. –Prosencephalon sep. to diencephalon and telencephalon

Question 11

Talk through the specific structures that arise from each vesicle.

Answer 11

See slide 16 to check yourself.

Cerebral cortex, basa ganglia

thalamus, hypothalumus, retina

midbrain

cerebellum, pons

medulla

Question 12

What does the lumen of the neural tube become?

What is the choroid plexus?

Answer 12

Ventricular system

•Choroid plexus is vascular tissue + pia + ependymal cells
–Makes CSF
–Not in aqueduct nor spinal cord

Question 13

What forms the C shape of the brain?

Answer 13

cortical development around the insula

Question 14

What are the two signaling systems that pattern the dosoventral axis?

Answer 14

Sonic hedgehog (Shh) = secreted signaling molecule; initially expressed in the notochord (N)- planar signaling

Bone morphogenetic proteins (BMPs) = secreted signaling proteins with a variety of functions; expressed in ectoderm (ECT)- lateral signaling

Shh = ventral; expressed in notochord and floorplate (F)

BMPs = dorsal; expressed in epidermis

Question 15

What happens once the nural tube is closed?

Answer 15

Once the neural tube is closed, the roofplate expresses one signal and the floorplate expresses a second signal. These signals are responsible for patterning dorsal and ventral regions of the spinal cord, respectively.

Question 16

What is the Bell-Magendie law?

Answer 16

HUH?

Question 17

What does the mantle zone become?

Marginal?

Where do neurons start out?

Answer 17

Mantle zone becomes gray matter,

marginal zone becomes white matter.

Neurons start out in the ependymal zone (also known as the ventricular zone). Mantle zone is also known as the intermediate zone. Ependymal zone becomes less populated as neurons move out. Use this to desribe how you work your way out.

Question 18

Describe neurogenesis?

Answer 18

Progenitors become radial glia and then can develop into either neurons or glia.

Both neuroepithelial and adial glia are considered pluripotent.

Question 19

At what point in development is it decided wether a cell will become a neuron or a glia?

Answer 19

?

Question 20

Where does Adult take place?

Answer 20

?

Question 21

In the formation of the brainstem: myelencephalon, what does the roof plate form?

Alar plate

Basal plate

Answer 21

ependymal…. choroid plexus

sensory nuclei for CN VII-X

motor nuclei or CN VII-XII

Question 22

Metencephalon forms two divisions, what are they and what do they become?

Answer 22

1)Dorsal division looks like medulla
A)Alar plate forms cerebellum

1. Develops from Rhombic Lip

B)Sensory Cranial Nuclei (V)

2) Ventral division, basal pons contains pontine nuclei. This doesn’t follow typical dorso-ventral patterning

Question 23

What does the mesencephalon form?

Answer 23

Alar plate of the mesencephalon forms the corpora quadrigemina

(Inferior colliculi and Superior colliculi)

GSA of CN V is another alar-derived nucleus

Tegmentum

Basal plate of the mesencephalon forms GSE and GVE of CN III

GSE of CN IV

Question 24

What does the diencephalon form?

Answer 24

Alar plate is largely thalamus

Basal plate is largely hypothalamus

Roof and alar plates give rise to epithalamus (habenula and pineal)

Optic cup, another derivative, becomes CN II

Question 25

What are the two waves of formation for the telencephalon?

Answer 25

Initial pattern of gray and white matter development is similar to that of the rest of the neural tube.

The neocortex (or neopallium) undergoes a second pattern of development to allow for many layers (6)

Question 26

What role do radial glia have in addition to acting as neural progenitors?

Answer 26

?

Question 27

Formation of the Neocortex is……?

Answer 27

Laminar. oldest neurons are deepest

Question 28

What are the layers of the neocortex?

Answer 28

Layer I—Mostly die (latest to develop)

Layer II–Small and med. pyramidal neurons

LAYERS II and III connected between hemispheres via corpus callosum

Layer III—Small and med. pyramidal neurons

Layer IV—Stellate and granule

MOSTLY RECEIVE SENSORY INFO

Layer V—Large pyramidal neurons

Layer VI (first to develop)

Question 29

What is the fate of neural crest cells?

Answer 29

•Neural crest forms the majority of the peripheral nervous system
–Autonomic Ganglia
–Spinal nerves
–Schwann cells
–Melanocytes
–Adrenal medullary cells
–Pia
–Arachnoid
–Tendons of facial musculature

Question 30

Where are cranial nerves derived from?

Answer 30

neural crest around axis of neural tube.