Neuro Development Flashcards by Lauren Bradshaw

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

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3 germ layers

1: ectoderm
2: mesoderm
3: endoderm

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ectoderm forms the..

entire nervous system

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mesoderm forms the..

connective tissues (bone, tendon, cartilage, blood, etc.)

musculoskeletal system

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endoderm forms the..

linings of all cavities (GI tract, stomach, pancreas)

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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

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invagination

process of cells migrating underneath and displacing underlying cells to form the 3 germ layers

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day1

fertilization

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day 6

implantation

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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

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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

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Neural induction

notacord releases a substance that induces the NS to start forming

(part of mesoderm creates notochord–> becomes nucleus propulsus later in life)

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Neural plate

a thickening of the ectoderm caused when cuboidal epithelial cells become columnar

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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

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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)

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neural crest cells

specialized cells that eventually go to dorsal lateral surface, later they form the peripheral NS (i.e. ganglion)

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embryo at 21 days

picture slide 9

neuro tube –> progresses at either end

eventually lateral sides fuse together in the middle to form tube

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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)

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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

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sulcus limitans

eveything ventral= motor

everything dorsal= sensory

mantle layer= grey matter
marginal layer= white matter

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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

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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