Neurodevelopment

Question 1

What are the three layers of the gastrula

Answer 1

Endoderm (inner layer) gut, lungs, pancreas and liver
Mesoderm (middle layer) muscle, connective tissue
Ectoderm (outer layer) skin and neural plate

Question 2

Outline the stages of the neural tube formation

Answer 2

-neural plate invaginate, forming the neural groove
-fold deepens and eventually separate from the rest of the ectoderm to form the neural tube

Question 3

What is the caudal region of the neural tube

Answer 3

Spinal cord

Question 4

What is the rostral region of the neural tube

Answer 4

Brain

Question 5

Outline what secretes BMPs (Bone morphogenetic proteins)

Answer 5

-ectoderm cells synthesis and secrete BMPs
-organiser cells secrete BMP inhibitor (chordin, noggin, follistatin)

Question 6

What are the functions of BMP

Answer 6

-suppress the potential for neural differentiation and promote epidermal differentiation
-allows ectodermal cells to differentiate into neural tissue

Question 7

Outline the 3 vesicle stage of neural tube regionalisation

Answer 7

-proencephalon (forebrain)
-mesencephalon (midbrain)
-rhombencephalon (hindbrain)

Question 8

What are the neural tube flexures that occur during neural regionalisation

Answer 8

Cervical flexure- between spinal cord and hindbrain
Cephalic flexure- between midbrain and hindbrain

Pontine flexure- occurs later on

Question 9

How do the two brain vesicles divide into the 5 vesicle stage

Answer 9

Proencephalon- telencephalon + diencephalon
Rhombencephalon- metencephalon + myelencephalon

Question 10

What factors initiate the rostrocaudal patterning of the neural tube?

Answer 10

Wnt, FGFs and retinoic acid

Question 11

Outline Wnts role in rostrocaudal patterning

Answer 11

Wnt signalling activity level is low at rostral end and increases progressively in the caudal direction:
-mesoderm that flanks caudal region of the neural plate expresses high levels of Wnt
-endoderm that flanks the Ross trail region secretes Wnt inhibitors

Question 12

Outline ventral patterning

Answer 12

Notochord secretes sonic hedgehog (Shh)

Question 13

Outline the role of sonic hedgehog

Answer 13

-induces floor plate (specialised glial cells), which start secreting Shh
-induces ventral neurons
-drives cells to become motor (closer to the plate) and inter (further from the plate) neurons

Question 14

Outline dorsal patterning

Answer 14

Epidermal ectoderm secrete BMP

Question 15

Outline BMP in dorsal patterning

Answer 15

-Induce roof plate differentiation, which after closer of neural tube, starts expressing Wnt and BMP
-responsible for differentiation into sensory neurones

Question 16

Outline Wnts role in dorsal patterning

Answer 16

Proliferation of progenitor cells in the dorsal neural tube

Question 17

Outline the Hox gene family

Answer 17

Homeobox gene encodes a family of transcription factors that contain a homeodomain, regulate developmental processes
Mammalian genome contains 39 Hox genes, in 4 chromosomal clusters

Question 18

Outline the positioning of an induvidual Hox gene

Answer 18

The position within its cluster predicts it rostrocaudal domain of expression within the neural tube
-genes at 3’ positions are expressed in more rostral domains
-genes at more 5’ positions are expressed in progressively more caudal positions

Question 19

How is motor neurone identity controlled

Answer 19

Controlled by the spatial distribution of Hox gene expression
Local signals determine functional subclasses of neurones

Question 20

What divisions are involved in neural progenitor cells

Answer 20

Asymmetric:
-two neuronal progenitors- incr progenitor cells population
-onedifferentiated daughter and one progenitor cell- no amplification of progenitor cells population
Symmetric:
-two differentiated daughters- deplete progenitor cells population

Question 21

Outline radial migration

Answer 21

Excitatory neurones, originating from the cortical ventricular one, move along the long processes of radial glia cells to reach their destination

Question 22

Outline tangential migration

Answer 22

Inter neurons arise from progenitor cells in the ventricular zone of subcortical structures
Migrate dorsally to enter the cortex, once they reach a antero-posterior position they switch to a radial mode to travel to their final destination

Question 23

Outline free migration

Answer 23

-the PNS derive from neural crest cells
-neural crest cells are transformed from epithelial to mesenchymal cells, causing them to detach from the neural tube and migrate into the periphery

Question 24

Outline the axon growth cone

Answer 24

3 compartments:
-central core- rich in micro tubules, mitochondria
-filopodia- long thing processes, rich in actin, highly motile
-lamelipodia- motile structure, ruffled appearance

Question 25

How to attractive and repellent molecules guide axons across the midline structure

Answer 25

BMP acts as a repellent, directing axons ventricularly Netrin attracts axons Once the axons pass the floor plate, slit and robo act to repel them away, diminish their sensitivity to netrin to prevent midline recrossing Wnt guide axons growth rostrally at the ventral midline

Question 26

Name major functional regions of the mature CNS

Answer 26

-forebrain -mesencephalon -hind brain (midbrain) -spinal cord

Question 27

Outline the forebrain

Answer 27

-telencephalon, gives rise to the cortex, hippocampus, amygdaloid, basal ganglia -diencephalon, gives rise to the thalamus, hypothalamus and retina

Question 28

Outline the midbrain

Answer 28

Gives rise to the inferior and superior colliculi Controls many sensory and motor functions, including eye movement and the coordination of visual and auditory reflexes

Question 29

Outline the hindbrain

Answer 29

-metencephalon, gives rise to the pons and cerebellum -myelencephalon, gives rise to the medulla

Question 30

Outline the thalamus

Answer 30

Processes most of the information reaching the cerebral cortex from the rest of the CNS

Question 31

Outline the hypothalamus

Answer 31

Regulates autonomic, endocrine and visceral functions

Question 32

Outline the cerebellum

Answer 32

Modulates the force and range of movement, and is involved in learning motor skills

Question 33

I outline the pons

Answer 33

Conveys information about movement from the cerebral hemispheres to the cerebellum

Question 34

Outline the medulla oblongata

Answer 34

Includes several centres responsible for vital autonomic functions, such as digestion, breathing and heart rate control

Question 35

Outline the spinal cord

Answer 35

Recieves and processes sensory information from the skin, joints and muscles and control movements of the limbs and trunk

Question 36

Outline layer I of the cerebral cortex

Answer 36

(Molecular layer) contains dendrites of cells located in deeper layers and axons which travels through this layer to make connections in other areas of the cortex

Question 37

Outline layer II and III of the cerebral cortex

Answer 37

(External granular cell layer) Contains small pyramidal neurones and small spherical neurons (External pyramidal cell layer) Contains larger pyramidal neurons Axons of these neurons project locally to other neurons within the same cortical area, as well as to other cortical areas

Question 38

Outline layer IV of the cerebral cortex

Answer 38

(Internal granular cell layer) Contains large number of small spherical neurons. Main recipient of sensory input from thalamus. Is most prominent in primary sensory areas

Question 39

Outline layer V of the cerebral cortex

Answer 39

(Internal pyramidial cell layer) Contains pyramidial neurons, larger than those in layer III. They project to other cortical and subcortical areas and are the major output pathway

Question 40

Outline layer VI of the cerebral cortex

Answer 40

(Multiform layer) Contains neurons heterogenous in shape. It blends into the white matter and carries axons to and from areas of the cortex