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Brain development
| Term | Definition |
|---|---|
| CNS origins | Neural tube -> midline ectoderm dorsal to notochord specified to form neural tissue -> invaginates to form neural tube w/ neural plate region -> plate folding (neurulation) -> forms closed neural tube (spinal cord) |
| Neural tube defects | Spina bifida occulta -> small gap in spine but no dorsal opening/sac Myelomeningocele -> dorsal sac of fluid containing damaged spinal cord/nerves |
| PNS origins | Neural tube closure -> NCCs emigrate from dorsal neural tube to embryo Neurogenic placodes -> neurons delaminate from placode and migrate inside embryo -> coalesce w/ NCC-derived glia to form ganglia |
| What neurons do cranial NCCs form? | Invade pharyngeal arches/surround brain -> somatosensory neurons, cranial sensory ganglia, parasympathetic ganglia (ciliary III, pterygopalatine/submanidbular VII, otic IX), terminal parasympathetic ganglia X |
| What neurons do vagal NCCs form? | Caudal hindbrain -> invade heart/gut -> enteric neurons/glia |
| What neurons do trunk NCCs form? | DR neurons/glia and sympathetic ganglia |
| Axon growth cone | Actin/myosin interactions promote neuron motility -> moves towards suitable adhesive substrate -> regulated via adhesion and signalling |
| Axon scaffolds | Embryonic neuroepithelium, mechanical cues |
| Diffusible attractive molecules | Long range chemoattraction -> nerve growth factor (NGF) such as netrin |
| What does neurotrophic mean? | Nourishing -> promotes neuron survival/sprouting (NGF) |
| What does neurotropic mean? | Attractive -> growth cone chemotaxis -> promotes neuron directional growth |
| Diffusible repellant molecules | Long range chemorepulsion -> secreted semaphorins -> slit chemorepulsion |
| Contact repulsion molecules | Short range -> Eph ligands, transmembrane semaphorins, ECM (tenascins) |
| Contact adhesion molecules | Short range -> Ig CAMs, cadherins, ECM (laminin) |
| CAMs | Connect to growth cone cytoskeleton and signal transducers |
| What is the optic tectum? | Midbrain roof |
| Retinal axon growth to tectum | Retinal ganglion cell axons cross the midline -> navigate to optic tectum by following local guidance cues in neuroepithelium rather than diffusible signals released from target |
| Mechanical cues for axon growth | Axon grows towards softer tissue in vitro/vivo -> stiffness = high cell density |
| Retinotectal projection | Temporal retina -> contralateral anterior tectum Nasal retina -> contralateral posterior tectum Dorsal retina -> contralateral ventral tectum Ventral retina -> contralateral dorsal tectum Rely on counter gradients of ephrin/Eph in retina/tectum |
| Synapse formation in vitro | Promiscuous formation |
| Synapse formation in vivo | Axon guidance via NGF, ephrin, CAMs -> generic synapse formation via synapse specific adhesion molecules -> acitivty dependent selection (LTP stabilisation) |
| Ephrins in tectum | EphrinA in posterior tectum repels EphA axons from temporal retina EphrinB in ventral tectum attracts EphB axons from nasal retina |
Created by:
vykleung
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