1-2 development of the nervous system Flashcards
zygote
egg & sperm fertilize to create a zygote
46 chromosomes in 23 pairs
endoderm
precursor to organs, such as lungs & liver, & linings of the gut
mesoderm
precursor to bones, muscles, & blood
ectoderm
precursor to skin, eyes, & nervous tissue
nueral tube
precursor to CNS
cavity becomes the ventricular system of the brain
neural canal
center of the neural tube
ectodermal wall forms the rudiment nervous system
primary neuralation
cells of the neural plate invaginate & pinch off to form the tube
secondary neuralation
cells of the neural plate form a cord-like structure that migrates inside the embryo & hollows to form the tube
notochord
midline strip of cells between ectoderm & endoderm
component of mesoderm
neural plate
longitudinal band of ectoderm thickens to form the neural plate
neural plate border separates the ectoderm from the neural plate
dorsal induction
neural plate begins to fold inwards forming a longitudinal neural groove in the midline
neural groove deepens & neural folds approach each other toward midline
2 folds begin to fuse along neural groove
neural tube separates from ectoderm & becomes closed in the body
neural crest (from neural folds) separate from neural tube
sulcus limitans
longitudinal groove in the lateral wall of the neural tube
extends thru future spinal cord & brainstem & subdivides the gray matter in the walls of the neural tube into a alar & basal plate
alar plate
more dorsal
sensory processing
eventually becomes the cerebellum
basal plate
more ventral
motor processing
eventually becomes basal ganglia
neuropores
neural tube opening both cranial & caudally
neural tube defects
improper closure of the neuropores
rostral/anterior - anencephaly
caudal/posterior - spina bifida
1st branchial arch
mandibular
CNV
lower lip, ant tongue, middle ear
mandible, maxilla, zygomatic, & temporal bones
muscles: mastication, mylohyoid, tensor tympani
2nd branchial arch
hyoid
CNVII
stapes, stylhyoid, hyoid
muscles: facial expression, stylohyoid
3rd branchial arch
CNIX, CNXII
hyoid
post tongue, epiglottis
muscles: stylophayngeus
4th & 6th branchial arches
CNX
tongue, laryngeal cartilages, epiglottis
muscles: palatoglossus, pharyngeal constrictors, intrinsic larynx, esophagus
myelination
brainstem (& cranial nerves) @ 18-24 weeks
myelination starts at 5 months & continues well after birth
myelination of central pathways - postnatal adolescence
neural proliferation
starts at 5 weeks
generated in or close to the ventricular lining
cells divide & move either horizontal or vertical
vertical cleavage
early stages of development
splits along vertical axis & produces 2 daughter cells
horizontal cleavage
later development
splits along horizontal axis
only 1 of the daughter cells continues to proliferate
