Neurosicience development of the neurvous systems coursepack

Neuroscience Development of the Nervous System Thomas J Cusack, M.D., M.S Barrow Neurologic Institute Development of the Nervous System Gastrulation (week 3) • primary germ layers • Ectoderm • Mesoderm • Endoderm • Ectoderm • Neuroectoderm • Neural crest cells NEURO01_01_ Germ Layer Derivatives NEURO01_01_ Neural Plate Development • Neuroectoderm → CNS and PNS • Notochord induces neural plate development • Notochord remnant in adults→ nucleus pulposus • Neural tube closes • Neural crest cells develop NEURO01_01_ Neurulation Neurulation (week 3) • Sensory (alar) plate • Dorsal nerve roots • Motor (basal) plate • Ventral nerve roots • Dorsal and ventral roots join to form spinal nerves NEURO01_01_ Neural Tube Pathogenesis NEURO01_01_ Neuroscience Central Nervous System Divisions Thomas J Cusack, M.D., M.S Barrow Neurologic Institute Development of the Nervous System NEURO01_02_ Telencephalon Cerebral hemispheres Basal ganglia (most) Lateral ventricles Diencephalon Thalamus Hypothalamus Subthalamus Epithalamus Retina Optic nerves Third ventricle Mesencephalon Midbrain Cerebral aqueduct Metencephalon Pons Cerebellum Fourth ventricle Myelencephalon Medulla Fourth ventricle Neural Tube Defects Condition Anencephaly Description • • • • • • Example Failure of anterior neuropore to close Brain does not develop Incompatible with life ↑ serum and amniotic fluid AFP ↑ acetylcholinesterase Polyhydramnios Anencephaly, commons.wikimedia.org • Holoprosencephaly • • • Incomplete separation of the cerebral hemispheres One ventricle in telencephalon Seen in trisomy 13 (Patau syndrome) Associated craniofacial malformations Alobular_holoprosencephaly.wikimedia.org NEURO01_02_ Spina Bifida • Spina bifida occulta • • • Failure of posterior neuropore to close, or to induce bone growth around it Vertebrae fail to form around spinal cord No increase in AFP Asymptomatic; tuft of hair over defect Spina bifida with meningocele • • Meninges protrude through vertebral defect Increase in AFP • • Meninges and spinal cord protrude trough vertebral defect; seen with Arnold- Chiari type II Increase in AFP • • • Most severe Spinal cord can be seen externally Increase in AFP Spina bifida with meningomyelocele Spina bifida with myeloschisis Kaplan Anatomy Table IV-I-3 NEURO01_02_ ... Malformation • Failure of foramina of Lushka and Magendie to open → dilation of 4th ventricle • Agenesis of cerebellar vermis and splenium of the corpus callosum Excessive CSF and destruction of cerebellum... displacement of cerebellar tonsils through foramen magnum Type II • More often symptomatic • Downward displacement of cerebellar vermis and medulla through foramen magnum • Compression of fourth... cells of nervous system • Capable of cell division Astrocytes • Most numerous CNS glial cell type • Many radiating processes • Large bundle of intermediate filaments • Structural support of CNS