L13 GOK Flashcards
(23 cards)
whats the difference in axon collatorals in the invertebrate and vertebrate brain ?
invertebrate - few
vertebrate - many
modes of axon branching ?
arborisation - branching of axon terminals
bifurcation - branching of axon terminals
collateral formation - middle of axon branches
arborisation occurs where usually ?
within the target
whats a good example of delayed interstitial branching ?
layer 5 pyramidal neurons
what part of the developing neuron is involved in target selection ?
GC and axon shaft just behind GC
explain activity dependent collateral elimination
axons innnervate too many targets during development
collaterals pruned based on activity
- no activit eliminated/ die due to lack of stimulation
projections retained by Layer V neurons
are dependent on where they?
develop not where they are born
transplant motor neurons into the visual cortex - these neurons will project to the sup colliculus
in relation to topographic mapping which part of the brain has been widely studied ?
retina -> superior colliculus (mammals) or optic tectum
what is the sup colliculus involved in ?
eye movements particularly saccades
Visual field divided into ?
nasal and temporal , dorsal and ventral
temporal axons terminate where?
nasal axons terminate where?
T -rostral SC
N - caudal SC
who carried out experiments on frog RGC ?
Sperry
what did Sperrys eye experiements show ?
molecular mapping rather than functional molding of random connections
GAP 4 is a marker for what ?
growing axons
what is a membrane stripe assay ?
cut a strip out of retina explant with nasal and temporal sections and culture them on membranes isolated from caudal and rostal sc
what did the stripe assay show ?
temporal axons only grow on rostral membrane
nasal axons grow on both rostral and caudal membranes
why do temporal axons only grow on rostral membranes ?
why does boiling the axons causes ?
because they have receptors that respond to inhibitory signals from caudal membrane
denatures receptors and temporal axons grow everywhere
why do nasal axons grow everywhere ?
because they will have to pass through the rostral sc before they get to caudal
what type of repulsion are ephrins involved in ?
contactrepulsion
level of ephrin expression in rostral and caudal sc?
r - low
c - high
level of ephrin receptor expression in temporal and nasal axons
t - high
n - low
why do nasal only have a small number of receptors for ephrin ?
want to stop at caudal SC
low no. of receptors needs high ephrin signalling at caudal SC to collapse GC and stop migrating axon
dorsal and ventral parts of the retina eph B expression ?
D -low L - high
V - high M - low
receptors EphB d and V
ligand ephrin B L and M
