Lecture - Nervous System (Development + Disorders Jasoni)

Question 1

Slide 5 and 6: Neurulation

1. What layer of ectoderm, endoderm and mesoderm does the neural plate form from? What do the other two layers form?
2. What does the closure of the neural tube look like?
3. Which hole (anterior neuropore or posterior neuropore) closes first?

Answer 1

1. Entiretiy of NS is derived from ectoderm
2. Like a burrito
3. Anterior neuropore

Question 2

Slide 8: Consequences of abnormal neural tube closure: Anterior neuropore

1. What day if development does it close on?
2. Is the anterior part where the brain forms or the spinal cord?
3. What’s the term of the anterior neuropore failing to close?
4. So how does it reaming open lead to “without brain”?
5. If brain doesn’t form, what else doesn’t form?

Answer 2

1. 26
2. Brain (duh)
3. Anencephaly (rare that baby is born with () though)
4. Developing brain remains in contact with amniotic fluid so you get degreneration of brain tissue.
5. None of the surrounding structures form - like meninges, scalp, skull.

Question 3

Slide 9: Consequences of abnormal neural tube closure: Posterior neuropore

1. What day does this close on?
2. What is it called if there is failure to close of the posterior neuropore?
3. What’re the two types of #2 - and what’s the difference?

Answer 3

1. 28
2. Spina bifida
3. Meningocoel (myelomeningocoel) - posterior epidermis AND vertebral coloum remains open (if nervous system doesn’t form, then the overlying epidermis + vert won’t form).
   - Occulta - relatively minor bc the skin and vertebral coloum close, just not the pore. Get a little dent at the end of back

Question 4

Slide 12: Origin of CNS and PNS

1. Where does the entire PNS form from?

Answer 4

1. The migratory neural crest cells that are the cells ‘left behind’ when the neural tube pinches

Question 5

Slide 13: Timing and migration path determine fate of neural crest cells

1. What are the three paths and what does each form?
2. Where does the PNS come from?

Answer 5

1. Medial path (early migration)
   - sympathethic neurons and glia
   - adrenal medulla and chromaffin cells

Intermediate path (mid migration)

-DRG (sensory neurons)

-Glia (Schwann cells) of spinal nerves

Lateral path

• pigment cells (melanocytes)
  2. The parasympathetic nervous system is derived from the medial- most migratory route, along with the sympathetic. Because parasympathetic ganglia are out in the periphery, the neural crest cells that give rise to them need to migrate farther out into the developing body than those that give rise to the sympathetic (chain) ganglia.

Question 6

Slide 14: Abnormalities associated with failed neural crest development (PNS effects only)

1. First of all, why are there only PNS effects?
2. There are three dfferent abnormalities - what are they?

Answer 6

1. Bc the neural crest cells have nothing to do with the CNS (that’s the tube that’s already formed). They made the PNS.
2. Hirschsprung’s disease (aka megacolon)
   - lack of enteric NS, usually in regions of gut only, so no peristalsis. Happens bc failed migration of neural crest cells to specific gut segments

Neuroblastoma

-cancer derived from neural portion of neural crest cells = they lose control over proliferation

Neurofibromatosis

-deregulated proliferation of neural crest cells. See small bumps on skin bc Schwann cells are inluded in the deregulation so they clump togehter under skin

Question 7

Slide 15: The 2 primary brain vesicles

1. What are the two mechanisms that drive the growth of the rostra-most end of the neural tube expansion?
2. What’re the three major subdivisions of the brain?

Answer 7

1. Differential cell proliferation and also increase CSF
2. Fore, mid and hind brain

Question 8

Slide 16: Five brain vesiscle stage

1. So there is continued differential growth anteriorly - t_____ (inlcudes the cerebral cortex)
2. Diagram - what’s on the right?
3. What ventricles are each of the five stages associated with?

Answer 8

1. Telencephalon (cerebral cortex and basal ganglia)

2.

3. Telencephalon = lateral, diencephalon = 3rd, mid-brain = CA, and pons+medulla = 4th

Question 9

Slide 18 and 19: Acceleraed growth of cerebral cortex

1. So the cerebral cortex grows slower or faster than the rest of the brain?
2. What does that result in?
3. What strcutures ‘follow’ the cerebral cortex?

Answer 9

1. Faster
2. Loop around to fit into skull
3. Basal ganglia, ventricles and even fornix

Question 10

Slide 21-23: Layers of cerebral cortex

1. What do the cells have in common in each layer?
2. What’s the anatony of how the layers form?

Answer 10

1. Shape, axon trajectory and info input
2. There are three zones: ventricular zone, intermediate and marginal. Connecting the marginal with the ventricular is the radial glia. The progenitor cells that will form the cerebral cortex and glia are in the ventricular zone. They will at one time stop in their cycle and go up the radial glia to get to the marginal zone and make daughter cells which are nuerons. Then, the next set of progenitor cells will stop and go up and form the next layer etc. So the ventriclar layer is the ‘diving layer.’

Question 11

Slide 24-26: Problems with the layers

For each of the three problems, what’s the:

1. Cellular cause
2. Genetic cause (maybe just remember whether it’s autosomal or sex-linked)
3. Phenotype
4. Clinical consequence

Question 12

Slide 26-30: Axons growing

Explain how axons find their way

Answer 12

There are choice points or intermediate targets at which information is conveyed in the form of molecules in the environment about where to turn to reach the synaptic partners. Things that influence:

• chemorepellants
• chemoattractants
• fasiculating with pioneering axons

Question 13

Slide 31: Disorders of axon pathfinding: congenital mirror movements

What’s the

1. Cellular cause
2. Genetic cause (well, what is the gene meant to code for?)
3. Phenotype
4. What are failed development neural circuits believed to underpin?

Question 14

Slide 33-36: Development of the cerebral cortex

1. When does myelination stop?
2. In what region does it stop last?
3. What things can derail the brain development?