Neural Development

Question 1

What is neuralation?

Answer 1

The early process of differentiation from embryonic tissue to the development of the nervous system.

Specifically, it involves the development, folding, and closing process of the nerual tube from the neural plate.

Question 2

What is the chronological sequence of events involved in neuralation?

Answer 2

first the neural plate appears from the ectoderm.

Then a neural grove forms as the plate begins to fold. (18 days)

Then it closes first at the midpoint, then at the anterior to form the neural tube (3-4 weeks)

Cells proliferate in the neural tube, leading to the development of vesicles.

Question 3

What are the possible neural tube defects?

Answer 3

Failure of anterior to close–> anencephaly

Failure of posterior to close–> spina bifida

Question 4

What are the primary vesicles? What structure causes their developement? When do they start to develop?

Answer 4

Forebrain, Midbrain, Hindbrain, Spinal Cord

Neural Tube (cell proliferation after closing)

4 weeks

Question 5

What are the Secondary vesicles? What structure causes their development? At what time do they start to develop?

Answer 5

Secondary vesicles are the Primary ones with more specification:

Forebrain (Cerebral Hemispheres, Hypothalamus, and Thalamus), Midbrain, Hindbrain (Pons medulla and cerebellum), Spinal Cord

Neural tube cause their development

5 weeks

Question 6

How large is the brain at birth? How large is an adult sized? By what age does the brain reach adult size?

Answer 6

At birth: 300-350g

Adult size: 1250-1500g

Reaches adult size by age 4

Question 7

What occurs during the fetal period? At what time does this occur?

Answer 7

Cells begin to migrate.

8-10 weeks

Question 8

What is the result of cell migration (during which development phase is this happening)? When does this result occur (week or months)?

Answer 8

the development of the cortical layers during the fetal period

6 months

Question 9

At what time is the brain considered developed?

Answer 9

9 months

Question 10

What happens at the 5th month of fetal development to the brain?

Answer 10

Convolutions and sulci begin to develop over the smooth surface of the brain due to the increased cell density

Question 11

What parts of the cell is increased cell density attributable to?

Answer 11

glial cells, myelination, axons, dendrites,

Question 12

What is a teratogen? What are some examples? What can teratogens lead to? When are organ systems most affect by teratogens?

Answer 12

A teratogen is a threat to development. they are agents that can cause congential abnormalities and/or development inteferrance

Examples: infections, drugs, alcohol, radiation, environmental pollutants

Whatever organ system is rapidly developing during the introduction of the teratogens is the most affected.

Question 13

What are some threats to development during the pre-embryonic phase? The embryonic phase? the fetus phase?

Answer 13

Pre-embryonic- teratogens effect ALL cells and result in DEATH

Embryonic- bc of organ and tissue differentiation of this period, there is extreme sensitivity to teratogens. Exposure can lead to severe functional/morphological defecits.

Fetus- organ/tissue differentiation has passed, so less sensitivity. Exposure results in smaller number and size of cells.

Question 14

What are the six microscopic neural processes happening during gestation?

Answer 14

1. Cell proliferation
2. Cell differentiation
3. Cell migration
4. Synaptogenesis
5. Selective Cell Death/ Pruning
6. Myelination

Question 15

What is Cell proliferation?

Answer 15

The development of new cells (aka neurons). Most are developed by 4-6 weeks gestation. More are produced than will be needed.

Question 16

What is Cell differentiation?

Answer 16

The designation of different types of cells/neurons to serve different functions

Question 17

What is cell migration?

Answer 17

The movement of cells/neurons to their proper location in the CNS.

Glial cell guide the process.

Formed in an inside-out fashion (deeper layers created first)

Errors corrected by later pruning/cell death

abnormalties can lead to things like dyslexia, epilepsy and MR

Question 18

What is Synaptogenesis?

Answer 18

The phase where cells build their connections via extensions of the axons (terminal buttons/synapses) to dendrites

Begins at 7 weeks gestation, countinues after birth

cells that don’t create connections die

more created than needed.

Question 19

What is selective cell death/ pruning?

Answer 19

a microscopic gestational cell process that initiates at 7 months gestation (an continues thru life).

Cells without connections, erroneous cell migration cells, and extra synapses are eliminated.

Another decline at 4 years (reached peak size)

prenatal cell death is genetic. Post natal is based largely on experience.

Question 20

What is myelination?

Answer 20

Begins at 4-5 gesation and focuses on the primitive areas first (brain & spinal cord, aka the primary vesicles)