lecture 13- synapse stabilisation and induction Flashcards
what are the 3 morphological changes from growth cone to presynapse
filopodia retraction and tight junction formation
membrane and extracellular glycoproteins added
presynaptical vesicle formation
which three structures can form contacts in synapse selection
growth cones
axon branches
dendritic filopodia
what are the 2 ways of forming synaptic connections
preestablished presynaptic specialisations mark future synapses
random contacts form and these form synapses if theyre stable
what is specification
selection of an apropriate contact
what is induction
clustering of synaptic machinery
where are neurexins found
presynaptic membrane
where are neuroligins found
postsynaptic membrane
what does differential expression allow
neurons to select synaptic partners
what does differential localisation allow
allows for seperate exititory/inhibitory neurons
which three theories operate synapses in spine formation
dendritic spines develop independently of presynaptic inputs
presynaptic inputs induce spine formation
dendritic filopodia induce synapses in axons growing past them
which theory for spine development happens mainly in the cerebellum
independant development
which theory for spine development happens mainly in the forebrain
filaments inducing synapses growing past them
what is the overall effect in forming a neuromuscular junction
progressive clustering of AChRs under the nerve terminal
where is agrin secreted from
motor neurons
describe the conditions of a neuromuscular junction before receptor clustering
AChR mRNA expressed at low levels
AChR channels widely distributed at low density
describe the process of receptor clustering
agrin released by MNs
agrin binds to MUSK which
autophosphorylates and recruits Rapsyn
AChR clusters are recruited
ACh released which will activate the AChRs ONLY IN THE PRESENCE OF AGRIN
If there is no agrin, it will inhibit ACrH expression
this results in densly concentrated AChRs at the synapse but nowhere else
which other molecule can recruit AChR
neuregulin
in general, what does ACh activity supress
AChR mRNA
what happens when a MUSK knockout occurs
no AChR clusters
what does ectopic MUSK stimulate
synapse formation
when does synaptogenisis happen
as axons reach targets
many before birth
which synapses are more dense, excitatory or inhibitory?
exitatory
what does differential localization of neuroligins allow
separated innervation
why do we look at the NMJ
big
simple
accessible
what do MNs without agrin look like
disrupted NMJs
AChRs scattered throughout
