Development of the Brain

Question 1

Describe the process of neurulation

Answer 1

• stimulated when the notochord forms ventral to the neural plate (derived from ectoderm)
• a thickening is formed by the cells on the edge of the plate
• actin in apex of cells constrict to fuse the edges to form a neural tube
• it has a rostral neuropore (closes 25 days) and a caudal neuropore (closes 27 days)

Question 2

Describe a consequence of failure of the rostral neuropore

Answer 2

Anencephaly:

• no forebrain
• unreactive to light and sound
• usually stillborn

Question 3

Describe a consequence of failure of the caudal neuropore

Answer 3

Spina Bifida:

• displaced cerebellum and hydrocephalus
• 3 types: occulta, meningomyelocele, myeloschisis
• posterior protrustion of spinal cord

Question 4

Describe the role of folate in development

Answer 4

• supplement of folate in materal diet
• reduces risk of neural tube defects
• folate involved in DNA synthesis pathway in cell division

Question 5

Describe the formation of the walls of the forebrain, midbrain and hindbrain

Answer 5

3 swellings form at end of neural tube:

• forebrain (prosencephalon): lateral expansions - telencephalon (cerebral hemispheres) and diencephalon (thalamus)
• midbrain (mesencephalon): single central tube
• hindbrain (rhomboencephalon) - metencephalon (pons, cerebellum) and myelencephlon (medulla)

Question 6

Describe the development of the IV ventricle

Answer 6

sits closed before widening in development and forming a rood containing specialised cells that secrete CSF, with widening, dorsal elements become lateral

Question 7

Describe the development of the spinal cord

Answer 7

• in neural tube ventricular layer containing progenitor cells divide to form neurons/glia
• this forms mantle layer, some neurons grow processes and communicate
• this forms white matter/marginal layer
• a sulcus (sulcus limitans) forms which separates ventral (motor) from dorsal (Sensory)

Question 8

Describe the origin of neural crest cells and derivatives

Answer 8

origin: cells on neural groove change from epithelial to migratory = neural crest cells

Derivatives:

• skull (bone - odontoblasts)
• sensory and autonomic NS (ganglia)
• pigment cells (melanocytes)