Neuro Development Flashcards
Gastrulation
a phase early in embryonic development during which the single-layered blastula of the embryo is reorganized into a trilaminar (three-layered)
begins with the formation of the primitive streak
3 germ layers
1: ectoderm
2: mesoderm
3: endoderm
ectoderm forms the..
entire nervous system
mesoderm forms the..
connective tissues (bone, tendon, cartilage, blood, etc.)
musculoskeletal system
endoderm forms the..
linings of all cavities (GI tract, stomach, pancreas)
Primitive streak
13-14 days
area of active cell migration, cells start to migrate inward–>forms the 3 layers
–> invagination
can see a streak between amnion and yolk sac
invagination
process of cells migrating underneath and displacing underlying cells to form the 3 germ layers
day1
fertilization
day 6
implantation
Neurulation
day 16-18
=the formation of the NEURAL TUBE
starts with the notochord release factors that start the process of CNS development -neural induction
begins with the formation of the NEURAL PLATE
Neurulation accomplishes 3 major things in higher vertebraes:
1: creates the NEURAL TUBE- which gives rise CNS
2: creates the NEURAL CREST- which migrates away from the dorsal surface of the neural tube, and gives rise to a diverse set of cell types- forms the PNS
3: creates the epidermis-which covered over the neural tube once it is created
Neural induction
notacord releases a substance that induces the NS to start forming
(part of mesoderm creates notochord–> becomes nucleus propulsus later in life)
Neural plate
a thickening of the ectoderm caused when cuboidal epithelial cells become columnar
neural tube process
1: neural plate around 18 days
cells divide in ectoderm at different rates
2: neural groove
plate begins to invaginate into the ectoderm
as cells divide faster there is no room so it goes deeper
3: neural tube
* notocord develops
embryo at 20 days
picture slide 8
neuro tube is like a cylinder
ectoderm develops at different speeds; faster at periphery and slower medially- causes invagination in center (ventrally toward yolk sac)
bumps/ribs on side are the mesoderm (it grows around the NS like how the vertebrae surround the spinal cord)
neural crest cells
specialized cells that eventually go to dorsal lateral surface, later they form the peripheral NS (i.e. ganglion)
embryo at 21 days
picture slide 9
neuro tube –> progresses at either end
eventually lateral sides fuse together in the middle to form tube
embryo at 24 days
picture slide 10
Neural tube is complete! (except for the ends)
functioning nervous system!
lumen in middle will form ventricle system (heart)
neural tube will form brain stem, spinal cord and cerebrum
cerebrum>brain stem>SC (SC develops slowest, simplest- most undifferentiated)
neural epithelial layer
lumen of neural tube
single layer of cells
where all neurons (functioning units) and glia (CT cells in NS/helpers) come from
sulcus limitans
eveything ventral= motor
everything dorsal= sensory
mantle layer= grey matter
marginal layer= white matter
Primary vesicle stage
about 28 days..
Prosencephalon-forebrain- thalamus, cerebrum- divides into 2 parts
Mesencephalon- midbrain (ie brain stem)
Rhombencephalon- hindbrain- pons and medulla
Mylon?- spinal cord
cranial and cervical flexures
Prosencephalon=
forebrain- thalamus and cerebrum
divides into 2 parts
1: diencephalon
2: telencephalic vesicle
Mesencephalon=
midbrain- brain stem
Rhombencephalon=
hindbrain- pons and medulla
Secondary vesicle stage
~42 days
spinal nerves growing into each somite (PNS)
prosencephalon divides:
1: diencephalon- thalamus
2: telencephalon
mesencephalon- midbrain
metencephalon- pons and cerebellum
myelencephalon- medulla oblongata
cephalic flexure is the only one that doesn’t disappear in adulthood?
CNS at 3 months..
adult looking NS (cerebrum, cerebral hemispheres, diencephalon, midbrain, cerebellum, medulla and SC) but still smooth and continues to develop
3 months=peak time of neuron cell division (can’t get bigger w/out invaginating on itself –>sulci)
cell proliferation is at its peak at?
3 months and slows down rapidly at 6 months
neurons still divide until birth but rate has declined dramatically
cell hypertrophy is at its peak at?
6 months
neurons only
100x more glia cells than neurons
sulci=
invagination lines
brain at 6 months
sulci get more surface area but still relatively smooth
neuron division slows
glia cells at their peak division rate
brain at 9 months
neuron division stops
glia cells can continue throughout life but dramatically decline after 2 years
(glia cancers are quite common)
alar plate
dorsal horn
sensory neurons
basal plate
ventral horn
motor neurons
gray matter
not myelinated
undifferentiated
Mantle zone
SC=most undifferentiated
white matter
myelinated
Marginal zone
axons grow..
laterally
ependymal cells
no longer differentiating
summary slide??
slide 18
neurotube forms..
sensory and motor neurons and glial cells (CNS) and SP
neurocrest forms..
PNS, dorsal root ganglia= collection of neurons right outside the spinal cord right before the ventral and dorsal roots fuse- forms the pia and arachnode matter (meninges)
dura matter is from mesoderm
somites=
segmental mass of mesoderm in the vertebrate embryo. occurs in pairs along the notocord and develops into muscles and vertebrae
each somite is divided into:
1: sclerotome- bone
2: dermatome- sensory
3: myotome- muscle
myotome
is supplied by 1 spinal nerve
divides in 2 parts:
1: epaxial division-dorsal rami-extensor ms of neck and back
2: hypaxial division- ventral rami-neck, prevertebral and limb ms
cranial to cervical somites are occipital somites
preoctic myotomes
epaxial division
dorsal rami- extensor ms of neck and back
hypaxial division
ventral rami- neck, prevertebral and limb ms
post-otic somites (occipital)
give rise to muscles of the tongue; which are supplied by hypoglossal nerve
CN 12
-tongue ms (except palatoglossus (CN10)
extrinsic and intrinsic
pre-otic somites
cranial to occipital myotomes give rise to extraocular muscles of the eyeball which are supplied by 3rd, 4th and 6th cranial nerve
Premandibular mesenchyme
- CN3
- levator palpebrae superioris, sup, med, & inf
- rectus & inferior oblique
Maxillomandibular mesenchyme
- CN 4- superior oblique
- CN 6- lateral rectus
otic somites
balance and equilibrium
hearing
pharangeal (branchial) arches
develop during the 4th week in utero as a series of mesodermal outpouchings on the L and R sides of the developing pharynx
develop the neck and face
pharangeal arch 1
Mandibular arch
CN 5
muscles of mastication anterior digastric tensor tympani mylohyoid tensor veli palatini
pharangeal arch 2
Hyoid arch
CN 7
facial expression muscles
posterior digastric
stapedius
stylohyoideus
where myelinated axons form..
white matter
where neurons form..
gray matter
ears, eyes and tongue are..
SOMATIC
