Embryology of the Nervous System

Question 1

Name 4 neural derivatives of neural crest cells.

Answer 1

sensory neurons
sympathetic neurons
parasympathetic neurons
Schwann cells

Question 2

Name an endocrine derivative of neural crest cells.

Answer 2

adrenal chromaffin cells

Question 3

Name 2 non-neural derivatives of neural crest cells.

Answer 3

melanocytes
leptomeningeal cells (pia mater, arachnoid mater)

Question 4

What role does sonic hedgehog play in neurulation?

• -who secretes it
• -what changes does it cause
• -what happens to it

Answer 4

secreted by notochordal cells

binds to nearby ectoderm cells, causing:

• -hypertrophy
• -changes in cell shape
• -changes in developmental fate

has endogenous autoproteolytic properties, so it doesn’t last very long before it chews itself up

Question 5

What role does BMP play in neurulation?

• -who secretes it
• -what changes does it cause

Answer 5

secreted by ectodermal cells

binds to nearby neuro-ectodermal cells, causing them to:

• -break contact with neighbors
• -change shape
• -migrate away

Question 6

Why don’t chromaffin cells grow axons?

Answer 6

chromaffin cells are in the adrenal medulla. the adrenal cortex secretes glucocorticoids, which suppress the genes involved in axon formation.

Question 7

How do neural crest cells get to the gut?

Answer 7

via the pharyngeal arches

Question 8

What is Hirschsprung’s disease?

Answer 8

Normally neural crest cells are “motivated” to migrate all the way to the gut by GDNF being secreted along the way by cells of the foregut and midgut. In Hirschsprung’s disease, the neural crest cells travel as far as midgut but then poop out in the hindgut (lose their motivating factor). “congenital megacolon”

Question 9

Why is the PNS segmented?

Answer 9

Because somites are segmented - somites secrete chondroitin sulfate, which repulses axons so that they grow in a segmented pattern.