Development of the Nervous System Flashcards
During gastrulation what gives rise to nervous system
Ectoderm
What is the name given to the proliferation of the ectoderm in the dorsal midline?
Neural plate- notochord releases factors causing differentiation of these cells into neural ones, differentiating it from skin
What happens to the neural plate as it thickens?
It folds up the sides and eventually the two neural folds fuse to form a tube The space in the middle is the neural canal
What is the name given to the bunch of cells at the tip of the neural fold that are excluded in the fusion?
Neural crest
Which cells do the neural tube and neural crest cells give rise to?
Neural tube – all cells of the CNS Neural crest – all cells of the PNS
What is the name given to the wall of the neural tube?
Neuroepithelium
What three types of cells do neuroepithelium give rise to?
Neuroblasts – all cells with cell bodies in the CNS Glioblasts – these become neuroglia (astrocytes + oligodendrocytes) Ependymal cells – line the ventricles and the central canal
Are motor neurons produced from neuroepithelium?
Yes – although most of their axons are outside the CNS, their cell bodies are within the spinal cord
State four cell types that neural crest cells can differentiate into.
Sensory neurons of dorsal root ganglia and cranial ganglia Autonomic post-ganglionic neurons Schwann cells Melanocytes
What are the three layers formed by the differentiation of the neuroepithelium?
Ependymal, grey matter and white matter AKA germinal layer, mantle layer, marginal layer
Glioblasts show a similar pattern of differentiation to neuroblasts. State one difference.
Glioblasts can migrate into the white matter NOTE: glioblasts do not develop axons (but they do develop processes)
What guides the process of differentiation and migration?
Signalling molecules
Which factors are important with regards to signalling molecules?
Concentration and timing
What can the grey matter of the neural tube be divided into in spinal chord development?
Alar plates dorsally and basal plates ventrally
Which types of neurons do the alar plate and basal plate give rise to?
Alar plate – interneurons Basal plate – interneurons and motor neurons
Around 4 weeks, you get differentiation of the wall of the anterior neural tube to form three primary vesicles. Name these primary vesicles.
Prosencephalon Mesencephalon Rhombencephalon
Describe the changes that occur to these three vesicles in the week or so following their formation.
The first and third vesicles divide in two Prosencephalon -telencephalon + diencephalon Rhombencephalon - pons + medulla
What important structure begins to appear quite late in development (around 8 weeks) and where does it appear from?
Cerebellum – appears as an out pouching from the back of the pons
Describe the arrangement of motor, sensory and autonomic cranial nuclei within the brainstem.
Motor = medial Sensory = lateral Autonomic = in between
What structure divides the motor nuclei from the sensory nuclei in the brainstem?
Sulcus limitans
How do neuroblasts migrate from the inner membrane to the outer membrane in the brain?
They attach themselves to radial glial cells and climb up them towards the outer membrane Radial glial cells have their cell bodies anchored to the inner membrane and have a single long process to the outer membrane from the ventricles
What happens to neuroblasts that stay in the middle of the cortex?
They become the basal ganglia
How many layers of cells are there within the cerebral cortex?
SIX
What can a deficiency of folic acid in pregnancy lead to?
Spina bifida
What will prosencephalon become
Forebrain
What will mesencephalon become
Midbrain
What will rhombencephalon become
Hindbrain
What does prosencephalon divide into
Telenchephalon and diencepahlon
Rhombencephalon divide into
Pons Medulla and later cerebellum which comes out of pons
3 layers to neural tube
Inside tube -> germinal layer->mantle layer->marginal layer
Migration of neuroblasts in neural tube development
Migrate into mantle layer forming grey matter and their axons project to white layer
What forms sensory neurones of spinal chord and dorsal root ganglion
Neural crest
What makes up rhomboencephalon in fully developed brain
Metencephalon and myelencephalon
Metencephalon
Pons and cerebellum
Myelencephalon
Medulla
Telencephalon
Cerebral cortex
Diencephalon
Thalamus and hypothalamus
What ventricles are in prosencephalon
Lateral
Third ventricle
Ventricles in mesencephalon
Aqueduct
Ventricles in rhomboencephalon
What is craniorachischisis
Failed closure of whole length of neural tube
What is anencephaly
Failed closure of rostral neural tube
Describe development of brainstem
Roof of neural tube proliferates laterally enlarging neural tube to from 4th ventricle. This pushes alar neurones laterally and basal plate medial
