Development of the CNS Flashcards
What are the different classes of cells within the differentiating neuroepithelium?
Neuroblasts- precursors for all neurons with cell bodies in the CNS.
Glioblasts- precursors for glial cells (astrocytes, oligodendrocytes).
Ependymal cells- precursors for cells lining ventricles and central canal.
What do neural crest cell differentiate into?
Sensory neurons of dorsal root ganglia.
Postganglionic autonomic neurons.
Schwann cells.
Non-neuronal derivatives, e.g. melanocytes.
What are the layers of the neural tube (inside-out)?
Ependymal (germinal) layer
Grey matter (mantle layer)
White matter (marginal layer)
Neural crest
Roof plate is dorsal and floor plate is ventral.
What controls differentiation in the developing CNS?
Signalling molecules, secreted by surrounding tissues, interact with receptors on neuroblasts.
Control migration and axonal growth by attraction and repulsion.
Depends on concentration gradient and timing.
What do neurons in the alar plate (dorsal) develop into?
Interneurons.
What do neurons in the basal plate (ventral) develop into?
Motor neurons and interneurons.
What do neural crest cells (lateral) develop into?
Sensory neurons in the dorsal root ganglion.
What are the main vesicles of the developing brain at 4 weeks?
Prosencephalon (future forebrain)
Mesencephalon (future midbrain)
Rhombencephalon (future hindbrain)
Future spinal cord
What are the main vesicles of the developing brain at 5 weeks?
Telencephalon and diencephalon (forebrain)
Midbrain
Pons and medulla (hindbrain)
What can be seen in the developing brain at 8 weeks?
Developing hemispheres, lateral ventricles and third ventricle in the forebrain.
Aqueduct in the midbrain.
Developing cerebellum and fourth ventricle in the hindbrain.
What are the major flexures in the developing brain at 4 weeks?
Cephalic flexure
Pontine flexure
Cervical flexure
What does normal development depend upon?
The coordinated completion of several complex processes: proliferation, differentiation, migration, axon growth and synapse formation.
What can interfere with processes of normal development?
Genetic mutation and environmental factors such as the mother’s lifestyle, diet, and teratogens.
What are neural tube defects? Give examples.
Result from non-closure of the neural tube.
Craniorachischisis- completely open brain and spinal cord.
Anencephaly- open brain and lack of skull vault.
Encephalocele- herniation of the meninges (and brain).
Iniencephaly- occipital skill and spine defects with extreme retroflexion of the head.
Spina bifida occulta- closed asymptomatic NTD in which some of the vertebrae are not completely closed.
Closed spinal dysraphism- deficiency of at least 2 vertebral arches, may be covered with a lipoma.
Meningocele- protrusion of the meninges (filled with CSF) through a defect in the skull or spine.
Myelomeningocele- open spinal cord (with a meningeal cyst).
Label the following diagram:
Label the following diagram:
