Dev of Nervous System Flashcards
when does the dev of nervous system start
3rd week of dev
explain how the neural plate is formed
ectoderm at the dorsal surface of embryo bet primitive knot and buccopharyngeal membrane thickens forming neural plate
describe the shape of neural plate
pear shaped and wider cranially
explain how the neural fold is formed
plate will develop a longitudinal neural groove that will deepen and as it deepens lateral edges elevate forming neural folds
explain how the neural tube is formed
neural folds will fuse starting at cervical region and extends in cephalic and caudal direction to from the neural tube
what are the open ends of the neural tube
anterior and posterior neuropores
when does the neural tube close
28 days in general
cranial neuropore - 25th
caudal neuropore - 28th
explain the difference from an open fold once that tube has closes
the tube sinks beneath the surface of the ectoderm
it refers to the 3 dilations of the cephalic end of neural tube
primary brain vesicles
what are the primary brain vesicles
prosencephalon
mesencephalon
rhombencephalon
what are the 2 flexures of the rhombencephalon
cephalic - midbrain
cervical - bet hindbrain and SC
what is the main thing happens at the 5th week of development
primary vesicles differentiate into 5 secondary vesicles
the ______ is continuous w the brain vesicles
central canal of SC
prosencephalon differentiates into what
telencephalon
diencephalon
mesencephalon differentiates into what
mesencephalon
rhombencephalon differentiates into what
metencephalon
myelencephalon
what separates mesencephalon and metencephalon
rhombencephalic isthmus
what separates metencephalon and myelenecephalon
pontine flexure
corresponding cavity/lumen of telencephalon
lateral vent
corresponding cavity/lumen of diencephalon
3rd vent
corresponding cavity/lumen of mesencephalon
cerebral aqeuduct of sylvius
corresponding cavity/lumen of metencephalon and myelencephalon
4th vent
discuss the formation of floor and roof plates of the SC
cavity of neural tube narrows to form a dorsiventral cleft with lateral walls and thin floor and roof plates
how are basal and alar plates formed in general
intermediate zone of the lateral wall forms large anterior thickening basal plate and small posterior thickening alar plate
compare basal and alar plate
basal - ventral, larger, motor
alar - dorsal, smaller, sensory
refers to the longitudinal groove bet dorsal and ventral horn cells
sulcus limitans
forms due to the continuous growth of basal plate
anterior median fissure
forms due to the continuous growth of alar plate
posterior median septun
what forms the central canal of the SC
narrowing of the lumen of the neural tube
how are intermediate zones of the SC formed
bc neuroblast cannot divide further they migrate peripherally to form intermediate zone
how are marginal zones of the SC formed
neuroblasts will also grow peripherally forming a layer external to the intermediate zone known as the marginal zone
what is the significance of intermediate and marginal zone in SC
intermediate - becomes gray matter of SC
marginal - becomes myelinated; white matter of SC
what do matrix cells give rise to
astrocytes, oligodendrocytes and ependymal cells
where do matrix cells come from
the wall of neural tube contains pseudostratified columnar epithelial cells
what happens to the neural tube as the development progresses
it elongates and remain small in diameter
what is the ventricular zone
zone directly after the cavity of neural tube composes of the neuroepithelial later
explain the connection of cell division and the neural tube
nuclei of cells move in towards the cavity to divide and outward to the periphery during intermitotic phases
what happens to cells once the neural tube closes
neuroepithelial cells give rise to neuroblasts
discuss the development of motor neuron
medial group - axons leave anterior surface of SC to supply muscles
lateral group - axons that leaves as autonomic preganglionic fibers
together they form the anterior root of SC
compare medial and lateral group of motor neurons
medial - motor cla sa mga muscles
lateral - supplies for ANS
what SC roots are autonomic preganglionic fibers
T1-L3
discuss the development of afferent neurons in sensory pathway
neural crest cells migrate to the posterolateral pos on both side of SC and differentiates into neuroblasts
what happens to central processes of afferent sensory neurons
becomes posterior root of SC
what are the 2 processes neuroblasts develop into
peripheral - axons of sensory nerve fibers
central - migrates to posterior part of SC and mapupunta either posterior gray column or sa marginal zone na white
how are posterior root ganglion formed
neural crest cells form the capsular/satellite cells that surround a unipolar nerve cell body
how are meninges in VC formed
from mesenchyme and ssurround nila neural tube
what is the length of VC and SC at 2 mo of development
same length but VC grows more so VC > SC
what is the significance of a longer VC than SC
ant and post roots of SN below L1 descend within the VC until they reach their IV foramen exits
what is filum terminale
pia matter that is attached to the coccygeal end of SC until coccyx; slender fibrous strand
what is cauda equina
horse tail
passes obliquely sa anterior and posterior roots of SN and filum terminale found at the lower end of VC
which secondary vesicle does the medulla oblongata come from
myelencephalon
discuss the initial formation of the medulla
initially may basal and alar plates separated by a sulcus limitans
the lateral walls will move laterally at higher levels expanding the 4th ventricle
in the formation of the medulla the basal and alar plates are separated by _______
sulcus limitans
in the formation of the medulla the lateral walls move laterally expanding the _______
4th ventricle
alar plates lie _____ to basal plates
lateral
neurons of basal plate of the medulla form motor nuclei of which cranial nerves
CN IX, X, XI AND XII
the motor nuclei from the basal plate are situated where in the cerebellum
floor of 4th ventricle medial to the sulcus limitans
neurons of alar plate from the medulla form which sensory nuclei of which cranial nerves/structures
CN V, VIII, IX and X
gracile and cuneate nuclei
how is the olivary nuclei of the medulla formed
others of alar plate migrate ventrolat and forms it
what are the nuclei formed from the medulla
basal - CN IX, X, XI AND XII
alar - CN V, VIII, IX and X anf gracile and cuneate nuclei
olivary nuclei
in the stretching of the lateral walls in forming the medulla what is its effect on the roof plate
it is stretched into a thin layer
in the medulla the vascular mesenchyme comes in contact with the roof plate and forms _______
pia matter; together called telachoriodea
vasculat tufts of tele choroidea project in the cavity of the 4th vent to form the _______
choroid plexus
_______ of tele choroidea project in the cavity of the 4th vent
vascula tufts
discuss what happens in the medulla between 4th and 5th months
2 lateral foramen of luschka and 1 medial foramen of magendie forms allowing connection of ventricles to subarachnoid space
the basal plate of the pons forms which motor nuclei
CN V, VI, VII
the ventromedial aspect of each alar plate of the pons form what
sensory nucleus of CN V, VII
vestibular
cochlear nuclei of CN VIII
pontine nuclei
axons of the pontine nuclei grow ________ (direction) and enters ______
transversely
developing cerebellum of opposite side
what does the entering pontine nuclei axons entering the cerebellum form
transverse pontine fiber and the middle cerebellar peduncle
the pons came from which secondary brain vesicle
ventral part of metencephalon
the cerebellum came from which secondary brain vesicle
posterior part of metencephalon
discuss how the formation of the cerebellum starts
alar plated bend medially forming rhombic lips
as as the alar plate enlarges the lips project caudally over the 4th vent and unite with each other at midline to form the cerebellum
discuss the dev of cerebellum at 12th week
vermis and cerebellar hemispheres are recognized
discuss the dev of cerebellum at end of 4th month
fissures develop on the surface now creating folia
how is the cerebellar cortex formed
neuroblasts from the matrix cells in the ventricular zone migrate to the surface forming the cortex
how is cerebellar nuclei formed
other neuroblasts will not migrate and they differentiate into cerebellar nuclei
what is superior cerebellar peduncle
axons of these neurons grow into the mesencephalon reaching the forebrain
what is middle cerebellar peduncle
axons of pontocerebellar and corticopontine fibers connect the cerebral cortex w the cerebellum
Hos is inferior cerebellar peduncle formed
from growth of sensory axons from SC and vestibular and olivary nuclei
what does the basal plate of the midbrain form
nuclei CN III and IV, red nuclei, subtantia nigra and reticular formation
what does the marginal zone basal plate of the midbrain form
basis pedunculi by the descent of fibers from the cerebral cortex to the pons and SC
what are the fibers that descend to form the basis pedunculi
corticopontine, cortiobulbar and corticospinal
what does the alar and floor plates of the midbrain form
superior and inferior colliculi
corresponding sense from superior colliculi
visual reflex
corresponding sense from inferior colliculi
auditory reflexes
discuss the path of CN IV fibers in the midbrain
emerge in the posterior surface of midbrain and decussate in the superior medullary velum
what brain vesicle is the forebrain from
prosencephalon
discuss the formation of the forebrain
floor and roof plate remain thin while lateral walls become thick tas mag kakaron ng lateral diverticulum
what is the lateral diverticulum in the forebrain called
optic vesicle
discuss the significance of the optic vesicle
rostral to it is the telencephalon and caudal to is the the diencephalon
from the optic vesicle what forms out of it
retina and optic nerve
what is present in the roof of diencephalon fate and what will it form
small diverticulum anterior to midbrain and it will become the pineal body
after forming the pineal body the rest of the roof of the DF will form the ______
choroid plexus of the 3rd vent
what arises in the lateral wall of the 3rd vent
thalamus from the thickening of the alar plate
in the DF what develops posterior to the thalamus
medial and lateral geniculate bodies
what occurs due to the continues growth of the thalamus
3rd vent narrows
define interthalamic connection in the DF
it refers to the fusion of 2 thalami through the 3rd vent
what will the lower part of the alar plate become to in the DF
hypothalamic nuclei and mamillary bodies
how is the infundibulum formed in the DF
comes from a diverticulum from the floor of the diencephalon
what originates from the infundibulum
stalk and the pars nervosa of pituitary gland (hypophyis)
what does telencephalon form
anterior end of 3rd vent
what closes the anterior end of 3rd vent
lamina terminalis
the diverticulum on either side of TF forms the _________
cerebral hemisphere
which stage of development does cerebral hemispheres rise
5th week of dev
relate the cerebral hemisphere and the intervent foramen
as cerebral hemispheres expand superiorly its walls thickens and intervent foramen reduces in size
the mesenchyme bet each cerebral hemi forms _______
condenses to form the falx cerebri
what does the CH form ant
frontal lobe
what does the CH form lat and sup
parietal
what does the CH form post and inf
occipital and temporal
describe the medial wall of the CH
remains thin and formed by epednymal cells
what occurs at the medial wall of the CH
invaginated by vascular mesoderm which forms the choroid plexus of lat vent
whaat separates the occipital lobe from the cerebellum
mesenchyme
what does the mesenchyme at OL form
condenses to from tentorium cerebelli
______ line the floor of the forebrain vesicle and proliferate producing ______
matrix cells; neuroblast
what is the significance of neuroblasts in the floor of forebrain vesicle
they form a projection that encroaches the cavity of the lat vent
refers to the projection that encroaches the cavity of the lat vent
corpus striatum
what forms from the dorsomedial portion of the corpus striatum
caudate nucleus
what forms from the ventrolateral portion of the corpus striatum
lentiform nucleus
name the lateral and the medial part of the lentiform nucleus
lat - putamen
med - globus pallidus
explain why the caudate nuc and the thalamus are close in contact
each CH expands and its medial surface approaches the lat surface of diencephalon kaya caudate nuc is close sa thalamus
discuss the longitudinal thickening in the CH and what does it form
it occurs walls of forebrain vesicle and protrudes into the lateral ventricle
hippocampus
discuss the asc and desc tracts in the CH nd what does it form
it forms and are forced to pass betw thalamus and caudate med and lentiform laterally
internal capsule
what happens at the cortex as the CH expand more
the gyri and sulci/fissures become more evident mga convolutions
how is the insula formed
cortex covering the lentiform remains fixed tas will get buried by overgrowth of the frontal, parietal and temporal lobes
discuss what happens to the matrix cells lining the cavity of CH
will produce many neurobalsts and neuroglia that migrate to marginal zone
what happens to the matrix cells that wont migrate to the marginal zone of CC
form the ependyma that lines the lat vent
describe the cortex at 12th week
it is very cerebellar due to migration of neuroblasts
describe the cortex at term
neuroblasts have differentiated and assumed stratified appearance due to result of incoming and outgoing fibers
type of cells in motor cortex
pyramidal
type of cells in sensory cortex
granular cells
it refers to the cephalic end of the nueral tube
lamina terminalis
what does the lamina terminalis become
septum pellucidum
it is the first commisure to develop
anterior commisure
where does the AC run and what does it connect
runs in lamina terminalis and connects the olfactory bulb and the temporal lobe on one side and to the same structures sa kabila
what connects the hippocampus in each hemisphere
fornix
what connects the CH
corpus callosum
largest and most important commisure
corpus callosum
formed in the inferior part of the lamina terminalis
optic chiasm
what forms the myelination in the CNS
oligodendrocytes
when does myelination begin at SC
4th month
discuss the manner of myelination in the SC
cervical and extends caudally
sensory muna last and descending motor fibers
when does myelination begin at brain
6th month pero fibers from the basal ganglia pa lang
discuss the manner of myelination in the brain intrauterine
6th month basal ganglia fibers - sensory fibers coming from SC but slow
discuss the manner of myelination in the brain at birth
largely myelinated
corticobulbar, corticospinal, tectospinal and corticopontocerebellar fibers begin to myelinate
is myelination complete at birth ?
not until puberty
what forms myelination outside of CNS
schwann cells
