Sem 4 Week 1 Lec 3

Front 1

What is neural induction?

Back 1

Specification of a region of the ectoderm which will form the neural plate on the dorsal surface of the embryo.

Front 2

When does the development of the nervous system begins in an embryo?

Back 2

At the end of the gastrula stage of embryogenesis with embryo having 3 layers of germ cells surrounding a primitive gut.(3rd week of embryonic dev.)

Front 3

What forms the skin and the nervous system?

Back 3

Outer layer-ectoderm

Front 4

What is the name of the critical event during neurulation?

Back 4

Neural induction.

Front 5

How does neurulation begin?

Back 5

When a sheet of ectodermal cells(neural plate) on dorsal surface transformed into specialized tissue from which entire Nervous system develops.

Front 6

Neural induction is an interaction between ectoderm and underlying mesoderm.

Back 6

True

Front 7

What is the notochord?

Back 7

Distinct cylinder of mesodermal cells which extends along midline of embryo.

Front 8

What does the notochord underlie?

Back 8

Portion of plate which will eventually become midbrain,hindbrain and spinal cord.

Front 9

Prechordal mesoderm gives rise to

Back 9

Forebrain.

Front 10

What are the candidate molecules for induction of forebrain structures?

Back 10

Follistatin,chordin,noggin.

Front 11

How does differentiation of subset of cells in the ectoderm into neural precursors occur?

Back 11

Inductive signals sent from mesoderm to ectoderm.

Front 12

How is neural tube formed?

Back 12

Neural plate buckles at midline--->edges of plate elevate and fuse at dorsal midline.

Front 13

Neural tube separates from overlying ectoderm.

Back 13

True

Front 14

What does the neural tube give rise to?

Back 14

All cells of CNS-brain & spinal cord.

Front 15

From where does the PNS arise?

Back 15

Neural crest cells.(also give melanocytes of skin)

Front 16

What are neural crest cells?

Back 16

Transient structure that arises from dorso-lateral margins of closing neural tube.

Front 17

Neural crest cells migrate away from dorsal neural tube.

Back 17

True.(epithelial-mesenchymal transition occurs and neural crest cells migrate extensively throughout body.

Front 18

What kind of cells do neural crest cells differentiate into?

Back 18

Spinal(sensory),autonomic ganglia,Schwann cells and melanocytes.

Front 19

Name one disorder of closure of spinal cord.

Back 19

Spina Bifida

Front 20

What factor is important in neural tube closure?

Back 20

Folic acid.

Front 21

As soon as neural tube closes,where does the formation of neurons and neuroglia occur?

Back 21

Rapid cell division in ventricular zone-inner surface of neural tube.

Front 22

In general,precursor cells can produce both neurons and glia.

Back 22

True.

Front 23

What determines specific fate of a neuron?

Back 23

Birthdate and environment.

Front 24

Neuronal tumours are rare.

Back 24

True.Most tumours are from glial cells.

Front 25

At the time of closure of neural tube,there is more than one layer of columnar epithelial cells.

Back 25

False.(Only 1 single layer of columnar epithelial cells-neuroepithelium)

Front 26

Neurons migrate along radial glia ,away from ventricular zone.

Back 26

True

Front 27

Give a brief summary of neurogenesis and gliogenesis.

Back 27

-neuroepithelial cells extend processes which span entire wall of neural tube.
-Cell nucleus migrate up process towards outer marginal zone where replication occurs.
-Nucleus migrates back to ventricular surface,retracts its processes and divides to produce 2 daughter cells.

Front 28

What happens to both daughter cells early on in the process of cell genesis?

Back 28

They remain in mitotic cycle.

Front 29

What process marks the birthdate and fate of a cell?

Back 29

After severeal divisions,a precursor cell will lose its ability to divide and will begin to migrate away from germinal zone to appropriate position in dev. NS

Front 30

Most progenitor cells are likely to unipotent.

Back 30

False.Most likely to be multipotent-producing glia and neurons.

Front 31

Where is the intermediate zone located?(formed as neural tube expands)

Back 31

Between ventricular and upper marginal zones.

Front 32

What happens during 4th-5th weeks of human embryonic dev. as a result of cells migration?

Back 32

Formation of 3 distinct swelling s or vesicles at rostral end of tube,in regions of future brain.

Front 33

What does the forebrain vesicle give rise to?

Back 33

Cerebral hemispheres and diencephalon.

Front 34

Midbrain vesicle gives rise to

Back 34

Adult midbrain.

Front 35

Hindbrain vesicle gives rise to

Back 35

Pons, medulla and cerebellum.

Front 36

What is lissencephaly?

Back 36

Smooth brain due to failure of cell migration.

Front 37

What causes agenesis of corpus callosum>

Back 37

Abnormal migration.

Front 38

Neuronal heterotopias occur due to

Back 38

Displacement due to abnormal migration.

Front 39

What is microcephaly?

Back 39

Small brain due to proliferation defects.

Front 40

Radial glia turn to astrocytes eventually.

Back 40

True

Front 41

Exposure to alcohol could affect

Back 41

Migration to superficial layers of cortex/ premature dismantling of radial glia.

Front 42

From where do immature,post-mitotic neurons migrate to their definitive location in dev. NS?

Back 42

From germinal zone.

Front 43

What is radial glia?

Back 43

Group of specialized supporting cells which form a scaffold along which immature neurons migrate.

Front 44

What is reelin?

Back 44

EC matric protein secreted by transient Cajal-Retzius cells located in the marginal zone of cerebral cortex(and hippocampus and cerebellum)

Front 45

What does reelin do?

Back 45

Arrests progress of neurons along radial glia.

Front 46

What happens when a neuron stop progressing along radial glia?

Back 46

Neuron leaves glial fibre take up definitive position within a cellular layer or nucleus.

Front 47

Which layer forms first?

Back 47

Layer 6

Front 48

How is the formation of layers in cerebral cortex?

Back 48

Inside-out(layer6,then layers 5-2)

Front 49

How is migration in dev. neocortex?

Back 49

Mainly RADIAL ,although some neurons undergo tangential migration from ganglionic eminences to reach destination(interneurons from subventricular proliferative zone)

Front 50

On what does regional diff. of cerebral cortex seem to depend on?

Back 50

Afferent input & intrinsic patterns of cell diff.

Front 51

Cerebral cortex is

Back 51

2-4 mm thick

Front 52

Cortical plate is associated with

Back 52

Beginning of cortex.

Front 53

Layer 5 is found on top of layer 6.

Back 53

True

Front 54

Layer 1 is the original marginal zone with no cells really.

Back 54

True

Front 55

When are most neurons formed?

Back 55

Between 10-18 wks of gestation.

Front 56

Lissencephaly can result in

Back 56

Mental retardation.(abnormal migration----> improper lamination)