Development of central nervous system

1. Development of central nervous system
Dr. Dikshya Upreti
PG Resident
Dept. of Psychiatry
National Medical College, Nepal

2. Division of Nervous system
Nervous system
Central nervous system
Brain Spinal cord
Peripheral nervous
system

3. Human embyonic and fetus development

4. Human embyonic and fetus development

5. Cell layers
There are three main layers of cell:
1. Inner most- Endoderm which gives rise to the muscle, lungs and
liver
2. Mesoderm gives rise to muscle, connective tissues, and the
vascular system
3. Outermost layer- Ectoderm which gives rise to entire nervous
system

6. Stages of development
During third week of development, the ectoderm on the dorsal
surface of the embryo between the primitive node and the
buccopharyngeal membrane thickens to form the neural plate.

7. Stages of development
 The plate develops a longitudinal neural groove(either side by
neural fold).
 Further, the neural fold fuse,
converting the neural groove
into a neural tube.
 Fusion starts from midpoint
then extends cranially and caudally.

8. Stages of development
 The cavity of tube remain in communication anterior and
posterior neuropores.
 Anterior neuropore closes first and the posterior neuropore 2
days later.
 Neural tube closure
is complete within 28 days.

9. Stages of development
The process of formation of neural tube is known as neurulation
and the embryo at this stage is called neurula.

10. Derivatives of neural crest cells:
 Neural crest are bilaterally paired strips of cells arising in the
ectoderm at the margins of the neural tube.

11. Stages of development
Meanwhile, the proliferation of cells at the cephalic
end of the neural tube causes it to dilate and form
three primary vesicles:
i. The forebrain vesicles
ii. Midbrain vesicles
iii. Hindbrain vesicles

12. The primary division of the developing
brain

13. Formation of neural tube
Neural tube is seen to dilate at the cephalic end into three
vesicle and rest of the tube elongates and remain smaller in
diameter; it will form the spinal cord and ventricular system of
the brain.

14. Spinal cord
 The wall of neural tube consists of neuroepithelial cells.
 They divide rapidly producing more and more neuroepithelial
cells.
 Collectively they constitute
the neuroepithlial layer.

15. Spinal cord
 Neuroepithelial cells give rise to another cell type, these are
the primitive nerve cells, these are neuroblasts which forms
mantle layer.
 The mantle layer later forms the gray matter of the spinal
cord.

16. Spinal cord
 The outer layer of the spinal cord, the marginal layer, contains
nerve fibers emerging from neuroblasts in the mantle layer.
 This layer takes white appearance and therefore called the white
matter of the spinal cord.
 As a result of continue addition of neuroblast to the mantle layer,
each side of the neural tube show a ventral and a dorsal thickening.

17. Spinal cord
 The ventral thickening – the basal plates - contain ventral
motor horn cells - form the motor areas of the spinal cord.
 The dorsal thickening - the alar plates - form sensory areas.

18. Spinal cord
 There will be longitudinal groove, the sulcus limitans, marks
the boundary between two.
 The ventral motor horn and dorsal sensory horn, the group of
neurons accumulates between the two areas and forms a
small intermediate horn.

19. Spinal cord

20. Congenital anomalies

21. Radial and Tangential patterns of Neurogenesis and
migration
 Dorsal forebrain give rise to the cerebral cortex.
 The cerebral cortex is the paradigmatic model of inside-to-outside
neurogenesis.
 The cell body containing nucleus and other organelles grow and has contact
with inner and outer surface of the cell wall of the brain.
 Outer is called pial surface of the brain and inner surface is inner surface of
neural tube; that goes into differentiation into ependymal lining of ventricles
in human brain.

22. Proliferation

23. Radial and Tangential patterns of Neurogenesis and
migration
 The cell body begin to translocate upward in the pial surface.
 Cell enter the stage where DNA replicate and then cell body begin to migrate
down towards the luminal surface of neural tube and cell divide
 Mitosis occurs and cell divide into symmetrical and asymmetrical from
which neuroblast will form.
 Cortical plate will be formed.
 Now, the neuroblast which are in ventricular zone should go to cortical plate
and this required migration.
 From the ganglionic eminence inhibitory neurons are produced and they
migrate in radial and tangential pattern.

24. Migration

25. Migration

26. Inductive signals

27. Cell death
Developmental cell death:
It is a reproducible, spatially and temporarily restricted death
of cells that occurs during the organism’s development.
Three types of developmental cell death are there:
1. Phylogentic cell death
2. Morphogentic cell death
3. Histogentic cell death

28. Cell death
Apoptosis:
 Major type, programmed cell death, involve specific
molecule that posses enzymatic activities.
 A failure to inhibit apoptosis is involved in cancers and
autoimmune disease(multiple sclerosis) and excess of
apoptosis is seen in neurodegenerative
disease(Alzheimer’s and Parkinson’s disease).

29. The neurodevelopment basis of psychiatric disease
 The increasing number of neuropsychiatric condition are considered to
originate during brain development, including schizophrenia, depression,
autism, and attention-deficit hyperactivity disorder.
 Schizophrenia: at the time of onset and diagnosis, the prefrontal cortex
and hippocampus are smaller and ventricles enlarged already at
adolescent presentation.
 In autism spectrum: the amygdala and fusiform gyrus demonstrate
abnormal attribution during facial recognition.

30. References
Snell’s clinical neuroanatomy 8th edition
Kaplan and Sadock’s Synopsis of psychiatry 11th
edition