Neurodevelopment

Question 1

Notochord

Answer 1

. Central event in gastrulation
. Distinct cylinder of mesodermal Ellis that condenses at midline of mesoderm and extensor from mid-ant. To post. Aspect of the embryo
. Generated by primitive pit surface indentation that elongates to primitive streak
. Disappears once early development is complete
. Sends inductive signals to overlying ectoderm that causes cells to differentiate into neural precursor cells

Question 2

Neuroectoderm

Answer 2

. Ectoderm that lies immediately above the notochord

. Will give rise to entire nervous system

Question 3

Neurulation

Answer 3

. Midline ectoderm thickens into distinct columnar epithelium (neural plate)
. On 18th day the neural plate invaginates along central axis to form neural groove that has neural folds on each side
. By end of 3rd week, the neural folds start to approach each other and fuse at midline converting neural plate into neural tube

Question 4

Neural crest cells

Answer 4

. Cells at lips of neural fold that lie btw neural tube and overlying ectoderm
. Migrate away from neural tube and give rise to PNS and other types fo peripheral cells

Question 5

Neural tube

Answer 5

. Walls thicken to rom brain and spinal cord

. Lumen is converted into ventricular system of brain and central canal of the spinal cord

Question 6

Spinal cord formation

Answer 6

. Proliferation/differentiation of neuroepithelial cells in developing spinal cord produce thick walls and thin roof/floor plates
. Differential thickening of lat. walls produces sulcus limitans (shallow longitudinal groove) on death side that separate alar plate (dorsal part) from basal plate (ventral part)
. Plates produce longitudinal bulges through length of developing spinal cord

Question 7

Alar plate

Answer 7

. Cell bodies form dorsal gray matter (dorsal gray horns in transverse sections)

Question 8

Basal plate

Answer 8

. Cell bodies form ventral gray matter( ventral horns in transverse section)

Question 9

Spinal ganglia

Answer 9

. Pseudounipolar neurons in spinal ganglia
. Derived from neural crest
. Form swellings on dorsal roots of spinal nerves (dorsal root ganglia)

Question 10

Brain formation

Answer 10

. Fusion o neural folds in cranial region and closure of rostral neuropore
. Form forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon) as primary brain vesicles

Question 11

Forebrain components

Answer 11

. Split during 5th week
. Telencephalon
. Diencephalon

Question 12

Hindbrain components

Answer 12

. Metencephalon

. Myelencephalon

Question 13

Flexures created during brain formation

Answer 13

. Midbrain flexure: formed by brain growing rapidly and bending ventral w/ head fold
. Cervical flexure: at junction of hindbrain and spinal cord
. Pontine flexure: between midbrain and cervical flexures in opposite directions

Question 14

Brain primary vesicle form what components of brain?

Answer 14

. Myecephalon: medulla oblongata
. Metencephalon: pons and cerebellum
. Midbrain: midbrain
. Forebrain: diencephalon and telencephalon

Question 15

Neurogenesis

Answer 15

. Mitotic division of non-neuronal cells to produce neurons
. Takes place in innerlayer of neural tube
. Cells gradually form closely packed layer of cells (ventricular zone)
. Eventually cells leave ventricular zone and begin transforming into neuron of glial cell

Question 16

Cell migration in nervous system development

Answer 16

. Massive movement of nerve cells to establish distinct nerve cell population
. Cells have to move over long distances to fill out brain

Question 17

Cell differentiation in neuronal architecture

Answer 17

. Cells reach destinations then begins o express particular genes for a specific phenotype
. Fate fo differentiating cell depends on where in the brain it is and when during development it is occurring and what the cell’s neighbors are doing
. Considered hallmark of vertebrate development

Question 18

Patterning along AP axis

Answer 18

. Ant. Portion of neural tube undergoes series of swellings, constrictions,a Nd flexures
. Caudal portion retains simple tubular structures and forms spinal cord
. Development characterized by sequential and hierarchical expression of different TFs at different times and in different parts of embryo

Question 19

Main factors in specifying properties of specific types of neurons, glia, and other cells

Answer 19

. Combination of transcription factors (TFs) they express

Question 20

Hox genes

Answer 20

. Conserved among animals
. Key role in assigning regional identities along AP axis
. Segmental pattern of Hox genes expression creates structure appropriate to particular AP position in the embryonic hindbrain while other 2 genes for TFs ems and otx play major roles in development of forebrain
. Expression of emx gene is restricted to the forebrain region and stop abruptly at its boundary w/ midbrain

Question 21

Patterning of neural architectures along AP and dorso-ventral axes

Answer 21

. Floor plate (specialized glial cells) along ventral midline
. Basal region of neural tube gives rise to motor neurons
. More dorsal alar regions give rise to interneurons
. Region most dorsal forms roof plate and neural crest

Question 22

Sonic hedgehog

Answer 22

. Signaling Protein
. Initially produced and secreted by cells of notochord just ventral to neural tube
. Ventral cells experience most sonic hedgehog expression to the ventrodorsal gradient is established in neural tube w/ high conc. In ventral regions

Question 23

BMP and Wnt proteins

Answer 23

. Generates dorsoventral gradient in roof plate
. Induces differentiation of dorsal regions of developing spinal cord
. Specialized differentiation is achieved through expression of particular combo of TFs that determine regional identity throughout CNS

Question 24

Synaptogenesis

Answer 24

. Establishment of synaptic connections as axons and dendrites grow
. Begin making synaptic connections w/ one another

Question 25

Neuronal cell death

Answer 25

. Selective death of many n. Cells
. Normal part of development
. Cell death is crucial phase of brain development
. Neurons compete for connections to target structures
. Cells w/ adequate bypasses remain, those w/o a place to form synaptic connections die

Question 26

Synapse rearrangement

Answer 26

. Loss of some synapses and development of others to refine synaptic connections
. Some synapses formed early in development are later retracted
. Takes place after period of cell death
. Which synapses are retained sesults from competition for tropic factors during development