Lec3: Brain Development 2

Question 1

What are the 5 stages of early brain development that ensure cell specification and germ layer development?

Answer 1

1. Gastrulation
2. Induction
3. Neuralation
4. Fusion
5. Vesicle formation

Question 2

Compare the plasticity and function of the 4 types of cells in early brain development.

Answer 2

In order of increasing function and decreasing plasticity/renewal:

1. Germ cells
2. Stem cells
3. Pluripotent Progenitor cells
4. Multipotent Progenitor cells –> highly specialised by this stage

Question 3

What are the proliferative layers of the Inner Cell Mass and what do they develop into?

Answer 3

1. Endoderm - lining of internal organs
2. Mesoderm - muscle, connective tissue
3. Ectoderm - Brain, skin

Question 4

Define gastrulation.

Answer 4

ICM (Epiblast) proliferates to form three primary germ layers

Question 5

Define induction.

Answer 5

Surrounding tissues secrete DIFFERENT CONCENTRATIONS of growth factor to influence the development and specialisation of different tissues.

Question 6

What are the inhibitors of Bone Morphogenic Protein 4?

Answer 6

Chordin and Noggin

Question 7

Describe the three different “pathways” of brain development of the ectoderm during induction in relation to the types of growth factor present.

Answer 7

1. BMP4 = Ectoderm to Epiderm (skin)
2. BMP4 inhibited (by chordin and noggin) = anterior neuroectoderm (brain)
3. BMP4 + FGF (Fibroblast -like growth factor) = posterior neuroectoderm (spinal cord)

Question 8

What do neural crest cells form?

Answer 8

SNS and PNS

Question 9

What do somites form?

Answer 9

Spinal vertebrae

Question 10

What are neural tube defects, and name three?

Answer 10

Pores form in the neural plate (incomplete closure)

1. Anencephaly - anterior neural plate
2. Spina Bifida occulta - posterior neural plate
3. Spina Bifida cystica - posterior neural plate

Question 11

How does Anencephaly appear?

Answer 11

Extreme underdevelopment or lack of development of brain.

Question 12

How does Spina Bifida Cystica appear?

Answer 12

Fluid-filled sac protruding from spine.

Question 13

At what week does the five-vesicle stage appear? Name each vesicle and what it develops into.

Answer 13

6 weeks in utero.

1. Telencephalon - Cerebral hemispheres
2. Diencephalon - Hypothalamus
3. Mesencephalon - Little development from here. 4 colliculi and midbrain have developed by now.
4. Metencephalon - Cerebellum
5. Myelencephalon - Pons + Medulla

Question 14

At what week does the three-vesicle stage appear? Name each vesicle and what vesicles they develop into.

Answer 14

1. Prosencephalon - Telencephalon + Myelincephalon
2. Mesencephalon - Corpora Quadrigemina
3. Rhombencephalon - Metelencephalon + Myelincephalon