Development of the Nervous System

Question 1

The CNS devel from where?

Answer 1

Neural tube

Question 2

What process produces the notochord?

Answer 2

Gastrulation

Question 3

What does the notochord produce?

Answer 3

Induces neurulation = conversion of overlying ectoderm to neurectoderm

Thickening and elevation of the neural plate = neural tube formation

Question 4

By what day is the NT completely closed?

Answer 4

28-32

Process takes place in 10 days

Question 5

Cranial neuropore closure defect can result in what?

Answer 5

anencephaly

Question 6

Caudal neuropore closure defect can result in what?

Answer 6

Spina bifida

Question 7

Describe spina bifida

Answer 7

Defect in closure of neuropore

Most commonly a defect in caudal (lumbosacral) neural tube to close

Untreated hydrocephalus = cognitive delay

Can contain – CSF, meninges and neural tissue

Question 8

Which neural tube defects are incompatible with life?

Answer 8

Anencephaly = failure of NT closure cranially, absence of cranial structure including brain

Rachischisis = failure of neural fold elevation

Question 9

How are neural tube defect diagnosed?

Answer 9

Raised maternal serum alpha-fetoprotein

USS

Question 10

How can neural tube defects be prevented?

Answer 10

Folic acid

Pre-conceptual and 1st trimester reduces incidence by 70%

Question 11

Briefly how does the nervous system devel from the neural tube?

Answer 11

Neuroectoderm tube has 3 sections
1) lumen forms ventricular system

2) 3 cranial dilations = 5 anatomical divisions of the brain
3) caudal tail spinal cord

Question 12

Outline how the spinal cord forms

Answer 12

Most of the length of the neural tubes gives rise to the spinal cord

When the spinal cord is the same length as the vertebral column the spinal roots must elongate – forming cauda equina

Question 13

Outline the development of the brain

Answer 13

During neural fold formation 3 primary brain regions form:

1) forebrain, 2) midbrain, 3) hindbrain

Theses become the primary brain vesicles

At 5 weeks of development five secondary brain vesicles are formed

Question 14

Describe hydrocephalus

Answer 14

Blockage of the ventricular system (tumour, infection)

Obstruct flow = accumulation of CSF

Question 15

What are the flexures of the NT?

Answer 15

Growth and development at cranial NT exceeds available space linearly, it must fold up

Cervical flexure

Cephalic flexure

Question 16

How do the ventricles of the brain form?

Answer 16

Tubular structures of the CNS persist through development

Question 17

What are neural crest cells?

Answer 17

Cells of the lateral border of the neuroectoderm tube

These cells migrate and contribute to a wide range of structures