1.7 Development of the Nervous System

Question 1

Describe the initial formation of the three germ layers

Answer 1

• Zygote is formed
• replicated into ball of cells; blastocyst
• Invagination
• In which forms endoderm (innermost), mesoderm, and ectoderm

Question 2

Describe the formation of the neural tube from the endoderm

Answer 2

• Section of endodedrm thickens into “neural plate”
• Neural groove forms rostral to caudal, creating neural crest
• Groove deepens and neural folds fuse dorsally

Question 3

Describe the differentiation of the five brain divisions once the neural tube has been folded

Answer 3

• At rostral end of neural tube, the prosencephalon (forebrain), mesencephalon, and rhombencephalon (hindbrain) have differentiated

Question 4

What are the precursors to the forebrain and hindbrain respectively?

Answer 4

Forebrain: prosencephalon
Hindbrain: rhombencephalon

Question 5

What are neuropores, and what is their function?

Answer 5

• Holes in either end of the neural tube post-neurulation.
• Allow for communication with amniotic fluid

Question 6

Which signalling molecules are produced at the dorsal vs ventral surface of the neural tube?

Answer 6

Dorsal: bone morphogenic proteins
Ventral: Sonic the hedgehog protein

Question 7

When bone morphogenic protein and sonic the hedgehog protein create different conc gradients in the developing neural tube, what does this cause?

Answer 7

• Two different patterns of development
• Sulcus limitans forms between two halves

Question 8

What is the name of the sulcus that separates the two halves of the developing spinal cord?

Answer 8

Sulcus limitans

Question 9

Which plate forms the precursor to the ventral/dorsal horn of the spinal cord?

Answer 9

Dorsal: Alar
Ventral: Basal

Question 10

From which cells are the cell bodies of sensory neurons derived from during the development of the spinal cord?

Answer 10

Neural crest

Question 11

At what week does the rostral aspect of the spinal cord differentiate into 3 vs 5 brain areas?

Answer 11

Week 4: Three areas
Week 5: Five areas

Question 12

In terms of growth, what causes the gyrencephalic appearance of the brain?

Answer 12

Grey matter grows faster than the white matter.

Question 13

Define Sudden Infant Death Syndrome

Answer 13

• Death of an infant under 1 year of age, unexplained after case investigation.
• Investigation includes autopsy, examination of circumstances, review of clinical history

Question 14

What are the three risks described in the triple risk model of SIDS?

Answer 14

• Vulnerable Infant
• Exogenous stressors
• Critical development period

Question 15

Describe the potential role of an immature nervous system in the pathogenesis of SIDS

Answer 15

• It is thought that SIDS occurs due to brainstem dysfunction, causing cardiorespiratory instability
• Peak SIDS incidence coincides with physiological changes in neural control of respiratory, cardiac, and sleep cycles
• Perhaps, in the case of SIDS, this results in defective control of these life-sustaining process, leading to death