Glossary of Cellular structure of cortex
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- Molecular Layer
- Superficial layer, rich in axon and dendrite fibers horizontally oriented.
Relatively few cell bodies (neurons)
No inputs or outputs
- External Granular layer
- Layer 2; mostly small neurons, a few small pyramidal neurons. input from layer 3 association fibers.
- External pyramidal layer
- Layer 3; medium-sized pyramidal cells, which give association and commisural fibers
- pyramidal cells
- have apical dendrites and several basal dendrites, give the cell a pyramidal shape.
- internal granular layer
- layer 4; composed of stellate neurons, and a few pyramidal neurons. Mostly receives thalamus input, especially in the primary somatosensory cortex.
- internal pyramidal layer
- layer 5; medium/large pyramidal cells, giant Betz pyramidal cells. these are so big cuz they project to subcortical areas.
- multiform layer
- layer 6; mixed bag; includes stellate, pyramidal neurons. the pyramidals project to thalamus.
- cell types in the neocortex
- glial, neurons
- neuron cell types in neocortex
- stellate, pyramidal, basket
- glial cell types
- microglia, oligodendrocytes, astrocytes
- Divisions of the cortex
- Isocortex (neo);
allocortex: paleocortex and archicortex
- olfactory center is an example
- hippocampal formation is an example
- half of brain's volume
- comprised of the cerebral cortex
- cortical connection fiber types
- association, commisural, projection
- association fibers
- interconnect cortex within the same hemisphere; primarily in layer 3 to layer 2
- arcuate fibers
- short association fibers that connect adjacent gyri
- longitudinal association fibers
- long, intercortical connections; like cingulate gyrus, superior/inferior occipitofrontal fasciculi, uncinate fasciculus.
- commissural fibersq
- interconnect the two cerebral hemispheres; such as corpus callosum, or anterior/posterior commisure.
- corticofugal systems
- projection fibers from the cerebral cortex layer 5 (large/giant betz pyramidal cells) to subcortical structures. 7 different systems
- corticothalamic system
- projection fibers from layer 5 of cortex to thalamus
- corticosubcortical system
- a re-entrant circuit; corticostriatal is an example, as it goes from corticostriatopallidothalamocortical loop. basically starts in cortex and ends in cortex.
- projection fiber from layer 5 of cortex 1) red nucleus, then subcortical structure
2)red nucleus to IO to cerebellum
- corticopontine system
- a projection system from layer five of cerebrum to the pons then to the cerebellum
- projection fiber system from layer 5 of the cerebrum to the reticular structures to subcortical structures
- corticobulbar system
- corticofugal system from the cortex layer 5 through the internal capsule, descend into the brain stem, emerge on either side of the mesencephalon as the cerebral peduncles, then synapse on lower motor neurons of c.n. 5,7, 9-12.
Motor inputs via superior colliculusand reticular formation for eye movement coordination.
- corticofugal projection system from the 5th layer of the cortex through the internal capsule in three tracts: corticobulbar, lateral corticospinal and anterior corticospinal; the tracts exit the internal capsule on either side of mesencephalon as cerebral peduncles.
- 7 corticofugal systems
- corticothalamic, corticosubcortical, corticopontine, corticorubral, corticoreticular, corticospinal, corticobulbar. all project from layer 5 except corticothalamic, from layer 6
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