exam 2 Flashcards
neurosurgery
t or f the retina cannot act as an organizer
false
eye is a neural tube. an outgrowth of the _____ (region of brain)
diencephalon
cilia and flagella can only be on the ______ surface of the epithelial cell
APICAL
sensory cells must have their apical surface facing toward or away from the fluid environment that the sensation moves through?
TOWARD
fluid is gone from what structure in the MATURE eye
optic vesicle
organize chronologically:
Retina, optic vesicle, optic cup
lens pit, lens placode, lens, lens vesicle
optic vesicle > optic cup > retina
lens placode > lens pit > lens vesicle > lens
retinal cell division takes place on the _____ side of the _____ layer and daughter cells that leave delaminate by penetrating _________
retinal cell division takes place on the APICAL side of the EPITHELIAL layer and daughter cells that leave delaminate by penetrating the BASAL LAMINA
individual cell clones are shown to extend linearly in the retina. Does this finding show that the cells are migrating VERTICALLY or HORIZONTALLY
Vertically, like in the cortex. from apical layer to granule cell layer
t or f. when following a progenitor cell on its clonal migration pathway in the retina, you should expect to see one cell type all the way through
false. vertical migration of progenitor clones results in multiple cell types (photoreceptors, neurons, glia), showing that these retinal progenitors are multipotent
in retina, expect what cell type to appear first, and what type to appear last? RPC, Ganglion, Muller glia
first= RPC and ganglion last= muller glia
a retinal progenitor cell that is NOT exposed to Neurogenin 2 cannot differentiate into _____. A retinal progenitor cell that is exposed to neurogenin 2 can differentiate into ______
NO neurogenin2 = NO retinal ganglion cells. bHLH TF
(but can differentiate into all other retinal cell types)
Yes neurogenin2= differentiation into ALL retinal cell types including Retinal ganglion cells
in retina, is neurogenin2 seen to be present early or late in development? explain
EARLY. Neurogenin 2 allows for differentiation of RPCs to retinal ganglion cells, the first cell group to usually show up in differentiation.
a retinal progenitor cell that is exposed to more neurod1 and math3 than math5 is directed toward what cell fate? how about vice versa?
\+++neurod1/math3 = amacrine cell \+++math5 = Retinal ganglion cell
what protein concentration remains constant during retinal development and is indicative of formation of late-born types?
[Casz1] remains constant throughout retinal development but is inhibited in early developmental stages by Ikaros. since there is less ikaros later on, there is more ACTIVE casz1, causing more late-born types
[casz1] remains constant throughout retinal development, but is inhibited in early developmental stages by ____
Ikaros. A KO of ikaros yields very few early-born types.
the presence of an miRNA that silences Ikaros would result in _____ (retinal development)
low amount of early born type cells, large amount of late born type cells due to increased activation of Casz1
t or f retinal cell fate is entirely stochastic
false, it is stochastic but the probability of a particular fate is the same as the proportion of that cell type in the mature retina. Weighted die
avian high acuity area (HAA) is specified by high concentrations of what and low concentrations of what
+++[cyp26] +++[FGF8] —[RA]. This area is devoid of rods and packed with cones. If retinoic acid is added to this area with an inhibitor of RA degradation, rods will be present in this area. This is just an example of the fact that there may be inherent biases in the strength of certain repressors over others
intracellular signalling for axon guidance particularly targets _____-based motility.
actin-based motility.
ECM molecules signal for changes in direction (attraction and repulsion) via various _____
integrins
cell-cell contact for axonal guidance- CAMS and cadherins are usually (positive or negative) signals for growth cone motility
positive (permissive)
cell-cell contact for axonal guidance- semaphorins and ephrins are usually (positive or negative) signals for growth cone motility
negative. Repulsive signals that cause the growth cone to stop. Doesn’t allow axon to grow past its correct target
t or f ephrins and eph receptors are an example of bidirectional signalling because binding of the two can cause cleavage of both
true
netrin-DCC signaling (attracts or repels) growth cones
attracts. diffusible signal
slit-robo signaling (attracts or repels) growth cones
repels. diffusible signal that causes growth cones to stop
axonal guidance- what neurons form a segmental ladder organization of the nervous system. they form what will become the major longitudinal tracts and commisures (rungs of ladder)
PIONEER NEURONS
retinal afferent (PIONEER) neurons normally project posteriorly through the diencephalon to the optic tectum (midbrain), if these are transplanted posterior to the tectum, where will they project? why?
pioneer neurons will project posteriorly still through the spinal cord dorsal white matter because they respond to global cues
If there is a semaphorin bridge that a pioneer axon must cross, and the guidepost cell on the other side of that bridge is missing, what will happen with the axon?
the axon will NOT cross the bridge, and will end up searching randomly for another guidepost cell on the original side of the bridge. semaphorin is a repulsive cue that cannot be crossed without a guidepost cell present for the pioneer
a fasciculin II KO would cause what in growth cone guidance
axons that are following other axons by cell-cell communication (fasciculation) will not be able to follow anymore and will not grow in a tract. will grow randomly
t or f neurons prefer certain substrates, and will grow to follow that substrate more often than cutting across a less preferred one
t. this is called adhesivity as a guidance cue. This correlation is really only present in ARTIFICIAL substrates
Why does semaphorin from the presumptive epaxial muscle direct LMC motor axons to the limb but not MMC? where does MMC go and why?
MMC motor axons go straight to presumptive epaxial muscle because the LHX3 that is expressed in them represses semaphorin receptors so repulstion does not occur. LHC motor axons have the semaphorin receptors so they are repressed from taking a route to innervate that muscle and are directed to the limb instead
LMC muscle innervation. In a Lhx1 KO, what region is not innervated?
dorsal portion is not innervated
LMC muscle innervation, what side of the body (D or V) does the LMCm innervate? what transcription factor causes this? how about LMCl?
LMCm= ventral, TF is Isl1 LMCl = dorsal, TF is Lhx1
an Ephrin knockout causes LMCl axons to innervate what region?
the ventral limb and NOT the dorsal limb anymore. Ephrin repels LMCl axons from the ventral limb
how does semaphorin repel LMCm axons from the dorsal limb?
LMCm axons produce neuropilin still after reaching their lateral region. LMCl axons reduce expression of neuropilin (a receptor of semaphorin) so they are not repelled by the semaphorin dense dorsal limb region. The ventral region has practically no semaphorin, so the LMCm is repelled by the dorsal region to here
why when the frog eye is taken out and rotated 180, does the temporal projection still go to the anterior tectum and the nasal projection to the posterior tectum?
cell membranes from the POSTERIOR tectal neurons REPEL axons from the temporal retina ganglion cells. they will always stay away from posterior tectum. High ephrin in the posterior tectum, high Eph in the temporal retina ganglion cells. Nasal retina ganglion cells have low eph, so they can reach the posterior tectum, whereas the temporal cells are stuck reaching only the anterior
forcing nasal retinal ganglion cells to express Eph will cause them to project to what area of the superior colliculus?
anterior (rostral). the superior colliculus has an ephrin concentration gradient with high concentration in the posterior (caudal) tectum
AXON GROWTH: Stabilizing microtubules are _____ (tyrosinated or acetylated)
acetylated
what happens when a filopodium encounters a permissive substrate?
the clutch is engaged- substrate is coupled to actin via a transmembrane receptor or something, so the actin is locked to that membrane site and can only grow forward, not be recycled backward. growth cone protrudes, cytoplasm and organelles fill up new C domain area, microtubules tighten up to form mature axon shaft
F-actin retrograde flow causes what for dynamic microtubules
clears dynamic microtubules from the P-domain. no longer exploratory because the engine is in idle
Cdc42 and Rac1 are what types of cues? do they repel or attract the growth cone
cdc42 and rac1 activate the growth cone. attractive
RhoA is an attractive or repulsive cue for the growth cone?
RhoA deactivates the growth cone. retract/repel
increased Ca2+ in the growth cone causes what
an attractive cue, cone turns toward that cue
TRP channel blocker in the growth cone causes what response for Ca2+? what happens to growth cone activity
growth cone does not respond to attractive cue (ie netrin, BDNF), no influx of Ca2+
what type of cells know how to delaminate for migration purposes
only IMMATURE NEURONS know how to delaminate from neurogenic epithelia (Neural crest)
Ephrin blocks neural crest cell migration across (anterior or posterior) somite
posterior. neural crest cells have eph receptors so will avoid high ephrin concentration in posterior somite
melanocytes, parasympathetic ganglia, enteric ganglia, sensory ganglia (dorsal root ganglia), sympathetic ganglia, and chromaffin cells are all derived from _________
trunk neural crest
if you put a quail cholinergic neural crest cell in a chick adrenergic neural crest region, what will likely happen to the cell
it will become an adrenergic fated cell, unless it is a PREDETERMINED neural crest cell- wont give new phenotype upon transplant
a neural crest cell that is constantly exposed to neuregulin will become _______
a schwann cell