Neurodevelopment Flashcards
What are the three layers of the gastrula
Endoderm (inner layer) gut, lungs, pancreas and liver
Mesoderm (middle layer) muscle, connective tissue
Ectoderm (outer layer) skin and neural plate
Outline the stages of the neural tube formation
-neural plate invaginate, forming the neural groove
-fold deepens and eventually separate from the rest of the ectoderm to form the neural tube
What is the caudal region of the neural tube
Spinal cord
What is the rostral region of the neural tube
Brain
Outline what secretes BMPs (Bone morphogenetic proteins)
-ectoderm cells synthesis and secrete BMPs
-organiser cells secrete BMP inhibitor (chordin, noggin, follistatin)
What are the functions of BMP
-suppress the potential for neural differentiation and promote epidermal differentiation
-allows ectodermal cells to differentiate into neural tissue
Outline the 3 vesicle stage of neural tube regionalisation
-proencephalon (forebrain)
-mesencephalon (midbrain)
-rhombencephalon (hindbrain)
What are the neural tube flexures that occur during neural regionalisation
Cervical flexure- between spinal cord and hindbrain
Cephalic flexure- between midbrain and hindbrain
Pontine flexure- occurs later on
How do the two brain vesicles divide into the 5 vesicle stage
Proencephalon- telencephalon + diencephalon
Rhombencephalon- metencephalon + myelencephalon
What factors initiate the rostrocaudal patterning of the neural tube?
Wnt, FGFs and retinoic acid
Outline Wnts role in rostrocaudal patterning
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
Outline ventral patterning
Notochord secretes sonic hedgehog (Shh)
Outline the role of sonic hedgehog
-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
Outline dorsal patterning
Epidermal ectoderm secrete BMP
Outline BMP in dorsal patterning
-Induce roof plate differentiation, which after closer of neural tube, starts expressing Wnt and BMP
-responsible for differentiation into sensory neurones
Outline Wnts role in dorsal patterning
Proliferation of progenitor cells in the dorsal neural tube
Outline the Hox gene family
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
Outline the positioning of an induvidual Hox gene
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
How is motor neurone identity controlled
Controlled by the spatial distribution of Hox gene expression
Local signals determine functional subclasses of neurones
What divisions are involved in neural progenitor cells
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
Outline radial migration
Excitatory neurones, originating from the cortical ventricular one, move along the long processes of radial glia cells to reach their destination
Outline tangential migration
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
Outline free migration
-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
Outline the axon growth cone
3 compartments:
-central core- rich in micro tubules, mitochondria
-filopodia- long thing processes, rich in actin, highly motile
-lamelipodia- motile structure, ruffled appearance
How to attractive and repellent molecules guide axons across the midline structure
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
Name major functional regions of the mature CNS
-forebrain
-mesencephalon
-hind brain (midbrain)
-spinal cord
Outline the forebrain
-telencephalon, gives rise to the cortex, hippocampus, amygdaloid, basal ganglia
-diencephalon, gives rise to the thalamus, hypothalamus and retina
Outline the midbrain
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
Outline the hindbrain
-metencephalon, gives rise to the pons and cerebellum
-myelencephalon, gives rise to the medulla
Outline the thalamus
Processes most of the information reaching the cerebral cortex from the rest of the CNS
Outline the hypothalamus
Regulates autonomic, endocrine and visceral functions
Outline the cerebellum
Modulates the force and range of movement, and is involved in learning motor skills
I outline the pons
Conveys information about movement from the cerebral hemispheres to the cerebellum
Outline the medulla oblongata
Includes several centres responsible for vital autonomic functions, such as digestion, breathing and heart rate control
Outline the spinal cord
Recieves and processes sensory information from the skin, joints and muscles and control movements of the limbs and trunk
Outline layer I of the cerebral cortex
(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
Outline layer II and III of the cerebral cortex
(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
Outline layer IV of the cerebral cortex
(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
Outline layer V of the cerebral cortex
(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
Outline layer VI of the cerebral cortex
(Multiform layer)
Contains neurons heterogenous in shape. It blends into the white matter and carries axons to and from areas of the cortex
