Lecture 5: nervous system Flashcards
neural tube differentiates into
CNS (brain and spinal cord)
anterior/ cranial neuropore closure
before caudal
day 25
posterior/ caudal neuropore
after cranial
day 28
notochord
has important role in inducing development of the spinal cord
primordial dilations
primary brain vesicles in the cranial end
prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)
spinal cord develops below
the level of the hindbrain
neurpepithelial layer
rapidly dividing neuroepithelial cells that form a thick, pseudostratified epithelium
neurogenesis and gliogenesis
occur simultaneously from proliferating neuroepithelial cells
-neurogenesis is more prominent in the embryonic period while gliogenesis is more prominent later in development
layers of the neural tube
- inner layer: ventricular zone
- intermediate layer: mantle zone
- outer layer: marginal zone
ventricular zone
- line canal and give rise to other layers (site of cell proliferation- contains neuroblasts)
- remaining cells form the ependyma (line the central canal of the spinal cord and ventricles of the brain)
mantle zone
- formed by neuroblasts
- becomes the gray zone of the spinal cord
marginal zone
-formed by neural processes that give rise to the white matter of the spinal cord
ventricular zone gives rise to..
all neurons and microglial cells
glioblast become…
astocytes or oligodendrocytes
microglial cells are derived from
mesenchymal cells and migrate into the CNS during the fetal period
ventral thickening of the mantle layer
basal plates- ventral motor horn cells
differentiate into voluntary motor neurons to innervate skeletal muscle
dorsal thickening of the mantle layer
alar plates - sensory are of the spinal cord
differentiate into interneurons and receive first input from sensory neurons of the peripheral NS
sulcus laminates of the mantle layer
a groove on each side that separates alar from basal
roof and floor plates of the mantle layer
no neuroblasts, pathways for nerve fibers crossing from one side to the other
intermediate zone of the mantle layer
lateral horns
differentiate to autonomic or involuntary motor neurons
growth of basal plate
nerve fibers of the basal plate grow out to form the ventral root
dorsal root ganglion
neural crest cells that migrate dorsolaterally give rise to the DRG
central processes of the DRG…
grow into dorsal horns
distal processes of the DRG…
meet the ventral roots to form a spinal nerve
positional changes of the spinal cord
3rd month
the spinal cord extends entire length vertebral column
-spinal nerves pass at the level of origin
positional changes of the spinal cord
6th monts
due to differential growth, the cord ends at higher levels
-the 1st sacral vertebra
positional changes of the spinal cord
birth
spinal cord ends at the level of the 2nd or 3rd lumbar vertebra
vertebral column and dura….than the spinal cord
grow more rapidly
the brain can be divided into 2 parts
- brain stem: similar to the spinal cord organization (alar and basal plates)
- higher centers (prosencephalon): specialized centers that lack the spinal cord organization-alar plates only
primary brain vesicles
- prosencephalon
- mesencephalon
- rhombencephalon
division of the prosencephalon (forebrain)
into the
- telencephalon
- diencephalon
division of the mesencephalon (midbrain)
does not divide
division of the rhombencephalon
into
- metencephalon
- myelencephalon
telencephalon gives rise to
cerebral hemispheres and lateral ventricles
diencephalon gives rise to
thalami, etc, and third ventricle
mesencephalon gives rise to
midbrain and aqueduct
metencephalon gives rise to
pons, cerebellum, and upper part of the fourth ventricle
myelencephalon gives rise to
medulla and lower part of the fourth ventricle
pituitary gland arises from
- ectoderm invaginations of the ectodermal stomatodeum (primitive oral cavity) called rathke’s pouch or adenohypophysis
- downward extension of the diencephalon called the neurohypophysis
rathke’s pouch (the surface ectoderm) forms
- pars distalis: anterior lobe of the pituitary gland
- par tuberalis: surrounds the infundibulum
- pars intermedia: adjacent to posterior lobe
infundibulum gives rise to
- median eminence
- infundibular stem
- pars nervosa (posterior lobe)
Adenohypophysis
– Formed from Rathke’s Pouch
• Out pocketing (diverticulum) of the ectoderm of the stomodeum (primordial oral cavity) that develops during week three
• Connection to the oral cavity degenerates during week six
• Hormones produced in the pars distalis or anterior lobe
Neurohypophysis
-Arises from the neuroectoderm of the diencephalon
•Infundibulum: down growth of the neuroectoderm of the diencephalon
• Nerve fibers from the hypothalamus grow into the infundibulum- hormones are produced in the hypothalamus and travel to the pars nervosa via axons
