TBL3 - Development of Neurons

Question 1

Describe the formation of the neural plate and neural folds

Answer 1

1) The central nervous system (CNS) appears at the beginning of the third week as a slippershaped plate of thickened ectoderm, the neural plate, in the mid-dorsal region in front of the primitive node
2) Its lateral edges soon elevate to form the neural folds

Question 2

Describe the development of the neural tube

Answer 2

1) With further development, the neural folds
continue to elevate, approach each other in the midline, and finally fuse, forming the neural tube
2) Ectoderm-derived neuroepithelium lines the neural tube lumen
3) During its differentiation into the spinal cord, neuroepithelium-derived neuroblasts form somatic motor neurons, interneurons, and presynaptic sympathetic motor neurons

Question 3

What is the function of the neural crest?

Answer 3

1) Isolated cells not incorporated into the neural tube form a strip of neuroectodermal cells—the neural crest
2) These cells migrate ventrolaterally along each side of the neural tube to form a series of somites
3) Paraxial mesoderm-derived somites form the spine
4) The neural crest separates the neural tube from the covering surface ectoderm
5) The neural crest ectoderm ultimately gives rise to PNS components, including dorsal root ganglia of spinal nerves, comparable sensory ganglia of cranial nerves, autonomic ganglia, and postsynaptic visceral motor neurons of the paravertebral sympathetic ganglia
6) Neuron bodies inside the CNS are derived from the neural tube; those outside, in the PNS, the neural crest

Question 4

What are Schwann cells and satellite cells derived from?

Answer 4

1) Schwann cells are neural crest cell derivatives

2) Satellite cells of the ganglia are modified Schwann cells

Question 5

What are neuroblasts, when do neuroblasts lose their ability to divide, and what is the clinical consequence of this loss?

Answer 5

1) Neuroblasts, or primitive nerve cells, arise
exclusively by division of the neuroepithelial cells. They develop into multipolar neuroblasts and with further development become the adult nerve cell or neuron
2) Once neuroblasts form, they lose their ability to divide
3) This impacts regeneration of neurons

Question 6

Which cell of the epidermis is derived from neural crest cells?

Answer 6

Melanocytes