1.3 Neural crest + Peripheral nervous system

Question 1

What is the neural crest?

Answer 1

Cell type only found in vertebrates (4th germ layer)
Migratory cell during development
Can differentiate into many cell types
Critical for evolution and success of vertebrates

Question 2

In what area does the neural crest develop?

Answer 2

From neural tube
Only from dorsal neural tube
Develops along whole A-P axis i.e. along neural tube

Question 3

What is neural crest induction?

Answer 3

FoxD3, SLUG - transcriptional repressor - binds to E boxes on promotors
Dorsal-lateral hinge point develops
Occurs towards end of neurulation
Express SLUG, repress epithelial phenotypes, promote mesenchymal phenotype
SLUG binds to E-boxes on promotors of specific genes typically those involved in cell adhesion - repression of these genes reduces cell adhesion

Question 4

What is neural crest delamination?

Answer 4

• neurons, schwann cells, pigment cells
  “escape” from neural tube
  epithelial-mesenchymal transition - migratory cells
  basal lamina of neural tube broken
  neural crest escapes on extracellular matrix

Question 5

What are neural crest derivatives?

Answer 5

Peripheral nervous system
Pigment cells
Bone, cartilage and connective tissue - only in head

Question 6

What is the peripheral nervous system?

Answer 6

Sensory neurons/ ganglia and their glia (in trunk)

Sympathetic/parasympathetic neurons and their ganglia and glia

Question 7

What is the sensory nervous system?

Answer 7

Sensory neurons sense the environment and send information via the spinal cord
Information flows from periphary to central nervous system.

Question 8

How are sensory neurons developed?

Answer 8

Neural crest migrates into somites

Differentiates into sensory neurons (DRG)

Question 9

What is the sympathetic/parasympathetic nervous system?

Answer 9

Sympathetic = uses energy
Parasympathetic = rest and digest
- control gut motility, blood vessel diameter, bladder control, energy release/storage (glucose)

Question 10

How does the sympathetic nervous system develop?

Answer 10

Neural crest migrates ventrally to sit near dorsal aorta

Question 11

What is the function of the sympathetic ganglia?

Answer 11

Near dorsal aorta

Sends signal that neural cells migrate towards

Question 12

How does the parasympathetic nervous system develop?

Answer 12

Neural crest migrates further ventrally to sit near gut, adrenal, heart and other tissues
Goes as far ventrally as exists in early development
Long migratory pathway

Question 13

What are the advantages of a peripheral nervous system?

Answer 13

Detect changes in environment - sensory system can detect attack
Respond to changes and attack swiftly in a co-ordinated manner

Question 14

What is the relevance of pigmentation?

Answer 14

Pigmented cells come from neural crest - melanocytes migrate under ectoderm and into the skin
Most common is melanin
Advantages = camouflage, attracting a mate, protection from UV damage

Question 15

Where are bone cartilage and connective tissue formed?

Answer 15

Neural crest only form these in head

Makes up most of vertebrate skull

Question 16

Where does trunk skeleton come from?

Answer 16

Neural crest is more ancient than somites - used to make whole body skeleton
Evolution of somites changed trunk not head - flexibility of axial skeleton to cranial skeleton
Bones of skull have a different function
- essentially outside
- helps protect eyes but is heavy