The development of the nervous system
- brain has precise interconnections among its 85 billion neurons
The endoderm, mesoderm, ectoderm
- the embryo begins life as 3 layers of cells: endoderm, mesoderm, ectoderm
un
Formation of the neural tube & neural crest
- formation of the notochord in the mesoderm during neurulation
=> cylindrical cord of cells => longitudinal axis
(induce ectoderm to
=> sends chemical signals: neural induction
thicken: neural plate)
- 18 days from conception: brain = flat sheet of cells
=> neural groove in the neural plate (rostral/ cranial to caudal)
=> walls of neural groove = neural folds => fuse dorsally forming the neural tube
=> some neural ectoderm pinched off + lie lateral to the neural tube: neural crest
during
delamination
(epithelial to
mesenchymal
transition)
- wall of neural tube (neuroepithelium) => central nervous system
- neural crest cells: peripheral nervous system
=> develop in close association w/ the underlying mesoderm
=> forms budges on either side of the neural tube: somites
=> vertebrae of spinal column & related skeletal muscles
, Signalling molecules
- communicate position, migration and differentiation of neural cells
- early in neurulation: signal dorsal-ventral pattern
=> Sonic Hedgehog (Shh) p secreted from notochord & floor plate
=> Bone Morphogenetic Proteins (BMP) secreted by roof plate
- antero-posterior pattern: Retinoic acid, Wnt, FGF (growth factors) At
gradient of high conc
ventrally & low conc dorsally
gradient of high conc dorsally
& low conc ventrally
Primary & secondary vesicles
- neural differentiation: structures become more complex & functionally specialised
=> at the rostral end of the neural tube: dvlp of 3 primary vesicles (4 weeks)
- by week 5: forebrain & hindbrain divide into 2 => 5 secondary vesicles
Prosencephalon
Mesencephalon
D
↓
Coptic resides)
Rhombencephalon
p
"I
"
↑
-
-
- the structure is hollow (creux) => enlarge & form the ventricles + central canal of spinal cord
Further brain development
- forebrain: formation of 2 telencephalic vesicles &
2 optic vesicles with the diencephalon at the centre
- brain has precise interconnections among its 85 billion neurons
The endoderm, mesoderm, ectoderm
- the embryo begins life as 3 layers of cells: endoderm, mesoderm, ectoderm
un
Formation of the neural tube & neural crest
- formation of the notochord in the mesoderm during neurulation
=> cylindrical cord of cells => longitudinal axis
(induce ectoderm to
=> sends chemical signals: neural induction
thicken: neural plate)
- 18 days from conception: brain = flat sheet of cells
=> neural groove in the neural plate (rostral/ cranial to caudal)
=> walls of neural groove = neural folds => fuse dorsally forming the neural tube
=> some neural ectoderm pinched off + lie lateral to the neural tube: neural crest
during
delamination
(epithelial to
mesenchymal
transition)
- wall of neural tube (neuroepithelium) => central nervous system
- neural crest cells: peripheral nervous system
=> develop in close association w/ the underlying mesoderm
=> forms budges on either side of the neural tube: somites
=> vertebrae of spinal column & related skeletal muscles
, Signalling molecules
- communicate position, migration and differentiation of neural cells
- early in neurulation: signal dorsal-ventral pattern
=> Sonic Hedgehog (Shh) p secreted from notochord & floor plate
=> Bone Morphogenetic Proteins (BMP) secreted by roof plate
- antero-posterior pattern: Retinoic acid, Wnt, FGF (growth factors) At
gradient of high conc
ventrally & low conc dorsally
gradient of high conc dorsally
& low conc ventrally
Primary & secondary vesicles
- neural differentiation: structures become more complex & functionally specialised
=> at the rostral end of the neural tube: dvlp of 3 primary vesicles (4 weeks)
- by week 5: forebrain & hindbrain divide into 2 => 5 secondary vesicles
Prosencephalon
Mesencephalon
D
↓
Coptic resides)
Rhombencephalon
p
"I
"
↑
-
-
- the structure is hollow (creux) => enlarge & form the ventricles + central canal of spinal cord
Further brain development
- forebrain: formation of 2 telencephalic vesicles &
2 optic vesicles with the diencephalon at the centre
