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• 1) Lack of tube closure- rhombic fossa, bridges medulla & pons
• 2) Basal Plate fusion across ventral midline forms Pons
• 3) Alar Plate fusion across dorsal midline forms Tectum of midbrain
• 4) Cell columns are adding for special senses and gill arch motor nuclei
• 5) Cranial nerves emerge- 12 cranial nerves
• 6) Flexure formations shape elongated tube to fit in cranium
• Cervical flexure- Neck region right angle bend
• Cephalic flexure- Mesencephalon right angle bend
• Rhombic flexure- pontine, reverse right angle flexure
• 7) Cerebellar emergence from roof plate of tectum
• 8) Ascending-descending pathways shift
• 9) Source neurons of modulatory transmitters- norepinephrine, serotonin, dopamine, acetylecholine