Embryology of the Nervous System

Question 1

Why is the nervous system the most suceptible to insult during the pre-natal period?

Answer 1

longest duration of development

first to begin & last to complete development

Question 2

Outline the process of neurulation to form the neural tube

Answer 2

• notocord causes differentiation of overlying ectoderm to neurectoderm > forming the neural plate
• lateral edges of neural plate elevate > forming a neural groove
• lateral edges form neural folds that fuse > forming the neural tube

Question 3

What condition can result if the anterior neuropore, or the posterior neuropore, fail to close normally during neurulation?

Answer 3

Anterior Neuropore

anencephaly (incompatible with life)

Posterior Neuropore

spina bifida

Question 4

What preconception and antenatal treatment can help reduce the incidence of neural tube defects?

Answer 4

Supplementary Folic Acid

Question 5

How does the length of the spinal cord and vertebral colum change during development?

Answer 5

at 3 months the spinal cord and vertebral column are equal length

at birth the spinal cord is shorter than the verterbal colum (conus medullaris ending at ~L1-L2) and the corda equina forms to allow spinal nerves the reach the lower limbs

Question 6

What are the 3 primary brain vesicles called at the cranial end of the neural tube, during neurulation?

Forebrain

Midbrain

Hindbrain

Answer 6

Forebrain (F)

• PROSencephalon

Midbrain (M)

• MESencephalon

Hindbrain (H)

• RHOMBencephalon
• around day 27*

Question 7

At 5 weeks of development the 3 primary brain vesicles further develop into 5 secondary brain vesicles, name the missing mature derivatives in this diagram:

Answer 7

Question 8

Summary of the anatominal divisions of the adult CNS

Answer 8

Summary of the anatominal divisions of the adult CNS

Question 9

As the neural tube elongates and exceeds the available space, at which junctions of the developing CNS do the following flexures develop:

Cervical Flexure

Cephalic Flexure

Answer 9

Cervical Flexure

spinal cord - hindbrain junction (rhombencephalon)

Cephalic Flexure

midbrain region (mesencephalon)

Question 10

In what form does the embryological neural tube remain as in the adult brain?

Answer 10

Ventricular System

interconnected reservoirs, filled with CSF

Question 11

What conditon can develop if there is an obstruction of the ventricular system of the brain?

Answer 11

Hydrocephalus

Question 12

What function is provided by the alar and basal plates in the nural tube?

Answer 12

Alar Plate (dorsal)

sensory function

Basal Plate (ventral)

motor function

this makes sense as the pattern is preserved in the spinal cord

Question 13

Where do the neural cresct cells come from?

Answer 13

population of cells that displace from the neural tube before it fuses

neuralectodermal in origin

Question 14

Name 3 derivatives of the neural crest cells

Answer 14

Dorsal Root Ganglion

Sympathetic Ganglia (chain)

Adrenal Medulla

Connective Tissue & Bone of Face/Skull

Question 15

What toxin are neural crest cells especially sensitive to insult from?

Answer 15

Alcohol