1. Steps in setting up the Nervous system Induction and Patterning of a neuron-forming region Birth and migration of neurons and glia Specification of cell fates Guidance of axonal growth cones to specific targets Formation of synaptic connections Binding of trophic factors for survival and differentiation Competitive rearrangement of functional synapses Continued synaptic plasticity during lifetime

2. Neuronal development Ectoderm differentiation: Epidermis, nerve tissue, or neural crest cells? Nerve tissue: Neuron or glial cell?

3. Neuronal development Ectoderm differentiation: Epidermis, nerve tissue, or neural crest cells? Nerve tissue: Neuron or glial cell?

4. Neuronal development

5. Nerve Outgrowth Filapodia-based movements Rely on Cytoskeleton and factors that rearrange the cytoskeleton (GTPases).

6. Types of Tissue organization in the Neural Tube

7. Spinal Cord

8. Cerebellum Important for motor control Purkinje fibers BMP and Granular layer

9. Movement of Neurons Glial cells serve as track. Nerve Birthdays: Determine how deep in the cortex a neuron will enter.

10. Cerebrum Similar to Cerebellum Neocortex: subdivided into 6 layers (old cells closest to ventricular zone). Cortex divided horizontally (approx. 40 sections). Fate decided early on (before S phase)

11. Cortical Neurons

12. Spinal Cord

13. Motor Neuron Specification Sonic hedgehog (Shh) secreted by floor plate.

14. Target specification of Motor neuron As Nerves pass through the cortex, different transcriptional regulators are expressed. Limb innervation determined by repulsion – If Lim1 is present, Eph A4 (receptor) is expressed; Eph A5 repels neuron – If no Lim1, neuropilin-2 expressed. (Axial muscles)

15. Following diffusible signals Netrin-1 and Netrin-2 SLIT and ROBO

16. Nerve Outgrowth Filapodia-based movements Rely on Cytoskeleton and factors that rearrange the cytoskeleton (GTPases).

17. Finding a place to hang out

18. Neural Crest Cells Neurons/glial cells of sensory, sympathetic, and parasympathetic nerves Epinephrine-producing cells of adrenal gland Pigment containing cells Skeletal/connective tissue of head 4 th germ layer?

19. Ventral Migration of Neural Crest

20. Neural Crest Cell specification

21. Neural Crest Regionalization Cranial – Cartilage, bone, cranial nerves, glia, connective tissues Cardiac – Melanocytes, neurons, cartilage, musculo-connective tissue wall of large arteries Trunk – Dorsal root ganglia, sympathetic ganglia, adrenal medulla, nerve clusters around aorta Vagal and Sacral – Parasympathetic ganglia of gut

22. Trunk Neural Crest Cells: Migration Dorso-lateral inhibited At first, between somites, but Semaphorin-3F causes movement through somites.

23. Further migration Cells that stop in sclerotome- dorsal root ganglia Cells past sclerotome-lack wnt and neurotropin receptors- parasympathetic and sympathetic nerves. BMPs from aorta convert cells to sympathetic and adrenal lineage Glucocorticoids- adrenomedullary cells. Neural crest cells committed to path early, but differentiate to determine final location.

24. Cranial Neural Crest Head is most anatomically sophisticated portion of vertebrate body. Mainly composed of neural crest cells

25. Cranial Neural Crest: Bone Formation

26. Neural Crest and neurocranium Viscerocranium (jaws, pharyngeal arches) well established as being of Neural crest origin…neurocranium controversial origin

27. The Face reflects the brain!

28. Cardiac Neural Crest

29. Cranial placodes