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Lecture 14

PSYO 2470 Lecture 14: Neural Development

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Dalhousie University
PSYO 2470
Stamp Jennifer

Neural Development Collections of neurons - o Gray matter – generic terms for collections of cell bodies in the CNS ▪ Stuff in middle of spinal cord o Cortex – means “on the outside” o Nucleus – central core ▪ Describes the centre of things ▪ For neuroanatomy – distinct mass of neurons, usually deep in the brain • clustered neurons o Substantia ▪ Used for groups of related neurons with less distinct borders of nuclei • More diffuse orders o Locus ▪ Small, well-defined group of cells • Essentially, a tiny nucleus o Ganglion ▪ Collection of neurons in the PNS • Collections of cell bodies in PNS Collections of axons - o Terms depend on where axons are found o Nerve ▪ Bundle of axons in the PNS • Only one collections of CNS axons is called a nerve – optic nerve o Not inside the brain, but is derived from the same embryonic tissue as central structures o White matter ▪ Generic term for collection of CNS axons o Tract ▪ Collection of axons that have a common site of origin and common destination • Used in CNS o Bundle ▪ Collection of axons that run together but don’t necessarily have same origin or same destination o Capsule ▪ Connect cerebrum or cortex to the brainstem • Ex. Internal capsule – connects brain stem to cortex o Commissure ▪ Connects one side of the brain with the other • Ex. Corpus callosum o Lemniscus ▪ Tract that meanders through the brain like a ribbon Early embryonic development - Initially – collection of indifferentiated cells after fertilization - Three distinct layers – differentiation o Invagination and folding – end up with 3 layers ▪ Endoderm – orange • Visceral organs o Gut organs ▪ Mesoderm – red • Gives rise to bones and muscle ▪ Ectoderm – blue • Nervous system and skin - Early nervous system o o Dorsal view ▪ Top of picture – anterior ▪ Stages of differentiation ▪ Forms from neural plate • Formation of neural groove - walls of the groove are the neural folds o Invagination ventrally – neural groove ▪ Neural folds form neural crest • Crest forms PNS ▪ Neural groove forms neural tube • Tube forms CNS o Neurulation – formation of neural tube and crest ▪ About 22 days after gestation - Disorders of neural tube development o o Anencephaly ▪ Problem with folding at anterior end • Means “no brain” o Spina bifida ▪ Consequence of failure of neural tube to close at posterior end • “cleft in two parts” - Brain vesicles o Entire brain derives from three vesicles ▪ ▪ Midbrain derives from mesencephalon ▪ Rhombencephalon – hindbrain ▪ Prosencephalon – forebrain o Cephalon – undifferentiated regions of the brain - Differentiation o o Procephalon gives rise to telencephalon – gives rise to the 2 cerebral hemispheres ▪ Grows laterally o Diencephalon ▪ Doesn’t grow laterally ▪ Differentiation o Hindbrain forms ridge at dorsal service o Olfactory bulbs develop from telencephalon ▪ Gives rise to optic nerves and optic tract o Midbrain ▪ Dorsal part become tecton • Superior and inferior colliculi ▪ Ventral part gives rise to tegmentum • Contains VTA (dopaminergic neurons that project to areas involved in motivation) • Gives rise to substantia nigra o Projects to parts of the brain involved in movement o Hindbrain (rhombocephalon) ▪ Gives rise to cerebellum o Differentiation of telencephalon/diencephalon ▪ ▪ Telencephalon gives rise to cortex ▪ Diencephalon gives rise to hypothalamus
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