Quiz Preparation 02/19 Flashcards
(44 cards)
What are the first signs of NMJ formation? (Synaptogenesis II)
Growth cone approaches myotube and makes an unspecialized contact.
How does the basal lamina contribute to NMJ formation after muscle removal? (S2)
It retains synaptic sites, guiding regenerating motor axons to original locations.
What occurs in laminin β2 knockout mice? (S2)
Active zones are poorly developed, and Schwann cells invade the synaptic cleft.
What role does rapsyn play in AChR clustering? (S2)
It anchors AChRs at synaptic sites in response to agrin signaling.
How does synaptic competition refine NMJ innervation? (S2)
Axons compete for control of each muscle fiber, with one axon strengthening while others retract.
What is the role of SNAP-25 in vesicle fusion? (NR)
SNAP-25 contributes two alpha-helices to the SNARE complex, stabilizing vesicle docking.
What is the function of complexin in neurotransmitter release? (NR)
It acts as a clamp to prevent premature fusion of vesicles before Ca2+ influx.
What are pegs, ribs, and beams in active zones? (NR)
Filamentous structures that position vesicles near Ca2+ channels for efficient release.
What is the function of synaptic vesicle recycling? (NR)
Maintains vesicle availability for sustained neurotransmission.
How does Ca2+ binding to synaptotagmin trigger vesicle fusion? (NR)
Ca2+ binding induces a conformational change that promotes SNARE-mediated fusion.
How do RIM proteins contribute to short-term plasticity? (AZ)
They regulate Ca2+ channel function and synaptic vesicle availability.
What role does ELKS play in vesicle docking? (AZ)
It helps maintain the readily releasable pool of vesicles at active zones.
What is the significance of the “T-bar” in Drosophila NMJs? (AZ)
It provides a scaffold for vesicle docking and fusion, ensuring rapid release.
What happens if Munc13 function is disrupted? (AZ)
Vesicle priming is impaired, reducing neurotransmitter release.
How do trans-synaptic adhesion molecules affect active zone alignment? (AZ)
They ensure presynaptic vesicle release sites align with postsynaptic receptors.
What imaging technique revealed the nanostructure of active zones? (AZ)
STED microscopy provided high-resolution images of active zone architecture.
What are the five stages of synaptic development? (S2)
Growth cone approaches myotube
Functional contact is established
Nerve terminal accumulates vesicles and basal lamina forms
Multiple axons converge, then are eliminated
Mature NMJ forms with specialized pre/post-synaptic components
What role does agrin play at the NMJ? (S2)
Agrin induces clustering of acetylcholine receptors (AChRs) at synaptic sites
What is the basal lamina’s role in NMJ formation? (S2)
It contains synaptogenic factors that preserve synaptic organization and promote reinnervation.
What happens to NMJ synaptic sites after denervation? (S2)
Axons regrow and preferentially reinnervate original synaptic sites due to guidance from basal lamina.
How does MuSK contribute to AChR clustering? (S2)
MuSK (muscle-specific tyrosine kinase) is activated by agrin via Lrp4, leading to rapsyn-mediated clustering of AChRs.
What happens in MuSK or agrin mutants? (S2)
AChRs fail to cluster, disrupting NMJ formation.
What are laminin beta2’s roles at the NMJ? (S2)
Laminin beta2 is essential for NMJ maturation; its absence results in impaired active zones and Schwann cell invasion.
How does synaptic elimination occur at the NMJ? (S2)
Initially, multiple axons innervate each muscle fiber, but competition leads to one axon maintaining synaptic contact while others are eliminated.
