Development of the Nervous System from Ectoderm

central nervous system

Develops from ectoderm.

peripheral nervous system

Develops from ectoderm.

neural plate

Dorsal thickening of ectoderm that represents primordium of nervous system, induced by notochord, mediated by shh.

neural tube

Forms from the neural plate and fold.

neuroepithelial cells

Single layer of cells that compose the neural plate and neural tube.

neuronal cells

Produced by neuroepithelial cells undergoing mitosis.

glial progenitor cells

Produced by neuroepithelial cells undergoing mitosis.

neural stem cell

Gives rise to neurons of the central nervous system and is the source of two types of macroglial cells in the central nervous system.

Astrocyte

One of the two types of macroglial cells in the central nervous system.

Oligodendrocyte

One of the two types of macroglial cells in the central nervous system.

bipotent progenitor cells

Gives rise to neuronal or glial progenitor cells.

neuronal progenitor cells

Gives rise to neuronlasts which later differentiate into numerous types of neurons.

Oligodedrocytes (Schwann Cells)
type-1 astrocytes
type-2 astrocytes

glial progenitor cells splits into

radial progenitor cells

from glial cells, act as guide wires in brain for migration of young neurons

microglial cells

- type of glial cells that doesnt originate from neuroepithelium
- functions as motile macrophages after damage to CNS
- derived from mesoderm and enter CNS along with vascular tissue

spinal cord

- develops from caudal third of neural tube

ventricular or neuroepithelial layer

- layer closest to the lumen of neural tube
- surrounded by intermediate or mantle layer

intermediate or mantle layer

- contains cell bodies of postmitotic neuroblasts and presumotive glial cells

grey matter

as the spinal cord matures, the intermediate layer becomes the -
- it is where cell bodies of neurons are located

ependyma
ventricular system

neuropepithelial layer becomes the - of the central canal and - of the brain

white matter

a peripheral marginal layer that contains neural processes but not neural cell bodies

basal plate
alar plate

addition of neuroblasts to the intermediate layer thickens each side ventrally and dorsally forming:

roof plate

left and right alar plates are connected dorsally over the central canal by thin

floor plate

two basal plates are connected ventrally by

FALSE

T OR F: roof and floor plate contain neuroblasts

white matter

marginal layer later develops into - of spinal cord
- has whitish appearance of tissue dominated by myelinated axons

funiculi

outer layer contains tracts of ascending and descending axons that are grouped together in bundles

ascensus medullae spinalis (ascent of spinal cord)

- non proportional growth of vertebral column and spinal cord, shift of spinal cord to a higher level

brain

- anterior two-thirds of neural tube develop into
- highly segmented structure

1. prosencephalon
2. mesencephalon
3. rhombencephalon

primary vesicles of brain

1. telencephalon
2. diencephalon

prosencephalon divides into 2 vesicles

cerebral hemisphere

lateral walls of telencephalon soon become domed and represent -

diencephalon

undivided portion of prosencephalon at anterior end of brain stem

1. metencephalon
2. myelencephalon

rhombencephalon divides into rostral and posterior portion

myelencephalon

resembles spinal cord developmentally and structurally and develops into medulla oblongata (posterior part of brain stem)

medulla oblongata

serves as tube between spinal cord and higher regions of brain
- for regulation of respiration and heartbeat

metencephalon

- anterior portion of rhombencephalon

1. pons
2. cerebellum

division of metencephalon

pons

transverse structure dividing the anterior ed of medulla oblongata

cerebellum

- phylogenetically newer and ontogenetically later developing structure

cerebellum

coordination centre for posture and movement

rhombic lips

- primordium of cerebellum
- dorsolateral regions of alar plates of metencephalon

vermis

medial part of anterior cerebellum

hemispheres

lateral area of cerebellum

mesencephalon

- does not divide
- structure remained simple between basal and alar plates

tectum

part of midbrain dorsal to aqueduct becomes - forming the corpora quadrigemina (derived from alar plates)

tegmentum

ventral to aqueduct the basal plates form -

diencephalon

- posterior part of prosencephalon
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- epithalamus (including epiphysis)
- thalamus
- metathalamus
- hypothalamus
- neurohypophysis
- optic cups

diencephalon gives rise to

thirs ventrical

the cavity developing within the diencephalon

1. adenohypophysis
2. neurohypophysis

hypophysis (pituitary gland) develops from 2 separate parts

adenohypophysis

- known as rathke's pouch
- ectodermal outpocketing of stomodeum in front of buccophryngeal membrane

neurohypophysis

ventral downgrowth of diencephalon, infundibulum

interventricular foramina

how lateral ventricle communicate with third ventricle

sulci

meaning grooves

gyri

meaning elevations

1. allocortex
2. neocortex

divisions of cerebral cortex

allocortex

- phylogenetically older division of cerebral cortex
- archicortex and paleocortex
- original part of cerebral cortex
- displays wide variety of histological patterns
- has 3 histological layers

neocortex

- newer division of cerebral cortex
- more complex 5 or 6 layered histological structure

1. molecular
2. pyramidal or granular
3. polymorphic

3 histological layers of allocortex

basal ganglia

neurons from intermediate layer of diencephalic form clusters of cell bodies known as

peripheral nervous system (PNS)

- consists of cranial, spinal, and visceral nerves and cranial, spinal, and autonomic ganglia

efferent nerve fibers

- motor, conduct impulses away from CNS

afferent fibres

- sensory, conduct impulses towards CNS

1. sympathetic
2. parasympathetic

- 2 efferent components of autonomic nervous system
- both contain preganglionic neurons, dervied from CNS and postganglionic neurons from neural crest