Lecture 9: Nervous System Embryology Flashcards
Metazoa (evolutionary history)
2 epithelial layers (endo/ectoderm) vs. single celled protozoa
Bilateria (evolutionary history)
Bilateral symmetry (primitive streak) vs. radially symmetric
Deuterostomes (evolutionary history)
Caudal to rostral gastrulation (“mouth second”) vs. protostomes (rostral to caudal)
Vertebrates (evolutionary history)
Dorsal spinal cord, rostral brain, basic body plan (extensive cephalization) vs. invertebrates (ganglion-centered brain plan)
Mammals (evolutionary history)
Neocortex expansion (cerebral cortex)
Primates (evolutionary history)
Expansion of association areas and frontal lobes; higher thought.
Mediolateral neural tube specification factors
Sonic hedgehog (SHH) = ventralizing factor
BMP4,7 = dorsalizing factors
Pax6,3,7 = alar (roof) vs. basal (floor) plates
What controls anterior-posterior specification?
Hox genes (super conserved among species)
How is the brain vascularized?
Vessels enter neuroepithelium area but maintain CT compartments, pulling CT and outer epithelial layer with them.
Blood-brain barrier composition
- Vessel endothelium cells + tight junctions
- Endothelial basement membrane
- Sometimes pericytes (CT fibers/cells)
- Astrocyte basement membrane
- Astrocyte foot processes
How are lipids regulated by the blood-brain barrier?
Free lipids bind apical transmemb./intracellular binding proteins on the endothelium and actively transported back to circulation by exosomes
Cerebral ventricles
CSF filled spaces (original neural tube lumen) lined by ependyma
Ependyma
Ciliated simple cuboidal/columnar epithelium that lines ventricles and produces + moves CSF. Forms the choroid plexus.
Choroid plexus
Comprises majority of CSF production. Contains superficial Kolmer cells (macrophages)
Hydrocephalus
Excessive fluid in the brain cavity caused by fluid overproduction, aqueduct occlusion, or poor absorption back to the blood
2 brain circulations
- CSF (ECF)
- Interstitial fluid
Anatomical/functional divisions of the neocortex
- Occipital lobe (vision)
- Temporal lobe (auditory)
- Parietal lobe (somatosensation)
- Frontal lobe (motor)
Wernicke’s area
Area in (usually left) parietal lobe, essential for language comprehension
Broca’s area
Area in (usually left) frontal lobe, essential for language production
Brain white matter composition
Fiber tracts, deep to cortcal surface. Connect cortical functional areas
Brain grey matter composition
Cortical sheet and nuclei/neuropiles of other tectal/tegmental areas
Gyrencephalic
Highly folded cortex
Lissencephalic
Non-folded cortex
Brain excitatory neuron structure
Long axons, well-defined dendritic trees
Brain inhibitory neuron structure
More local connections, diffuse arborization
Fast (ionotropic) NTs of the brain
-Glutamate (major excit. NT of cortex)
-GABA (major inhib. NT of cortex)
Slow (metabotropic) NTs of the brain
Monoamine NTs (regulatory purpose in CNS
-Dopamine
-Serotonin
-Norepi
-Epi
Fast + slow (nicotonic iono-, muscarinic metabo-) NT
ACh (NMJ)
Microglial cell
Resident macrophage of the CNS. Performs all brain immune functions and populates during fetal development
Oligodendrocytes
Myelinates CNS axons.
Astrocytes
Primary structural cell of the brain. Has perivascular end feet (BBB) and perineural feet (neuron nutrition). Controls the ionic milieu of the ECF.
Glial cells of the CNS
- Astrocytes
- Oligodendrocytes
- Microglia
Lens placode
Spheroid invagination of the surface ectoderm which becomes the lens
Optic stalk
Bulb shaped invagination of the neural ectoderm; future optic nerve.
Ganglionic eminences
Structures that develop laterally on the floor plate of the neural tube; develop into thalamic radiations, basal ganglia, cortical inhibitory neurons
