Neuromorphology Flashcards
at how many days does neurulation occur?
begins at 18 days
describe neurulation
thickeming of ectoderm that results in tall columnar cells in the neural plate on the dorsal midline of embyro
occurs immediately dorsal to notochord and results in the neural groove
neural groove becomes deeper d/t increased cell growth. eventually the dorsal neural crests meet and form a tube. this process occurs first in cervical region and progresses up and done
neural crest cells
neural crest cells are derived from the crests of the neural groove and the floorplate of the groove
become the sensory ganglia (such as dorsal root ganglia)
where does the ventricle system of the brain come from
the middle of the neural tube
how many cell layers thick is the wall of the neural tube?
1 cell
how does the neural tube close
closes both caudally and rostrally, leading down to anterior and posterior neuropore
what are the last parts of the neural tube to close?
anterior and posterior neuropore
anterior neuropore fails to close
anencephaly- death
posterior neuropore fails to close
spina bifida
spina bifida occulta- minor defect where lamina of vertebrae don’t fully fuse
meningocele- meninges bulge out of palce
meningomyelocele- spinal cord and meneinges are bulging out of canal. associated w/ damage to lower spinal cord and nerve roots
how cap spina bifida be prevented?
folic acid supplementation before pregnancy
cevical and cephalic flexure
after anterior neural pore closes, tube elongates faster than embyro can keep up. this causes a bends in the neural tube, called the cervical and cephalic flexures
how do the vesicles form?
after the anterior neural pore closes, the tube elongates faster than embryo can keep up. creates bulges in the transverse plans that become vessicles
rhombencephalic vesicle
at level of brain stem
mesencephalic vesicle
at level of midbrain
prosencephalic vesicle
most rostral vesicle. eventually differentiates into diencephalic vesicle and two telencephalic vesicles on either side of it
pontine flexure
an anterior flexure that forms in the rhombencephalic vesicle, which separates it into the mylenephalon caudally and metencephalon rostrally
lateral ventricles develop from?
telecephalic vesicles
third ventricle develops from?
diecephalic vesicle
what forms the cerebral aqueduct
mesencephalic vesicle
fourth ventricle develops from what?
metencephalic and myelencephalic vesicles
neural crest cells become what
dorsal root ganglia and all sensory nerves
ganglia of cranial nerves
autonomic ganglia- gut
adrenal medulla
schwann cells
leptomeninges
bone and connective tissues of face and skull
what is important for initiation of the neural tube
bone morphogenetic protein (BMP) is secreted by ectoderm and must be inhibited by noggin and chordin, which bind to BMP and inhibt it
where do noggin and chordin come from/
notochord
what does sonic hedgehog do?
secreted from notochord, (and eventually floorplate) causes ventral differentiation
what do TGF betas do?
secreted by neural crest cells secrete TGF beta like BMP to cause dorsal spinal differentiation. they are no longer inhibited by noggin and chordin b/c the neural tube is much bigger and thus the concentration are much smaller
why is cholesterol important for SHH?
SHH is released inactive
SHH is autoproteolytic, and cholesterol binds to N-terminus which is required for proper diffusion and activity
statins inhibit this and cannot be taken during pregnancy
basal/alar plate
basal- contains motor neurons
alar plate- becomes dorsal horn involved in sensory processing
in the brainstem, motor neurons are medial and sensory are lateral
why is retonic acid important
important for determining to rostral and caudal. diffuses from brainstem and activates Hox genes,
close to retnoic acid = caudal
certain acne drugs have retonic acid analogues, but cannot be taken during pregnancy
what do the cells in the wall of the neural tube become?
macroglia- cells of the CNS
what are notch 1 and numb
cell surface molecules- notch 1 occurs closer to pia and numb occurs basally
notch 1 signals cells to stop dividing, migrate away into mantle zone and mature
notch v delta
notch and delta are both cell membrane proteins that interact w/ each other.
when one cell upregulates notch, it down regulates notch on adjacent cells and upregulates delta. delta does the reverse.
this creates a good ratio of glia and neurons. glia are high notch cells
radial glial cells
they radiate from ventricle surface outward in waves, using surface markers on the glia
cajal retzius cells
found in layer 1, secrete reelin which is important for normal migration
what factors influence the differentiation of the neural crest cells
leukocyte inhibiting factor- sensory neuron
FGF2- sympathetic cell
stem cell factor- melanocyte
glucocorticoids- chromaffin cell
