week 6 lecture 2

These flashcards cover various aspects of the synaptic vesicle cycle, neuromuscular transmission, and related physiological processes, providing a comprehensive review for exam preparation.

What are the main stages of the synaptic vesicle cycle?

Loading, docking, priming, calcium sensing, fusion, endocytosis, translocation, sorting, mobilization.

What is the purpose of horseradish peroxidase (HRP) in studying endocytosis?

HRP produces a dense reaction product visible by electron microscopy.

What is the resting membrane potential determined by?

K+ concentration gradient across the membrane.

Define the term 'E_k' in relation to K+ concentration gradient.

E_k = 58mV log [K+ outside / K+ inside].

Which protein complex binds to synaptotagmin during synaptic vesicle endocytosis?

Adaptor protein complex AP2.

What is the role of dynamin in the synaptic vesicle cycle?

Dynamin is a GTPase responsible for vesicle fission.

What happens to vesicles when dynamin function is disrupted?

Vesicles do not recycle.

What is the typical time frame for clathrin-mediated endocytosis?

Takes 10s of seconds.

What technique combines channelrhodopsin activation with rapid freeze fixation?

Flash and freeze.

What does flash and freeze EM show about docked SVs?

Docked SVs have fused with the plasma membrane within 20ms.

What is observed in ultrafast endocytosis using flash and freeze EM?

Next to the dense projections immediately after fusion (20-100ms).

How do astrocytes contribute to the tripartite synapse?

They regulate the extracellular environment and respond to neurotransmitters.

What is a key function of gliotransmitters released by astrocytes?

They can regulate neuronal survival and synaptic strength.

What happens when glutamate is locally applied to an astrocyte?

It triggers a calcium wave that spreads to neighboring astrocytes.

What are the two types of neurotransmitter receptors?

Ionotropic receptors and metabotropic receptors.

What is the timeframe of action for ionotropic receptors?

Milliseconds.

What is the timeframe of action for metabotropic receptors?

Hundreds of milliseconds to minutes or hours.

What role does curare play in neuromuscular transmission studies?

It is a potent ACh receptor antagonist used to isolate the end-plate potential (EPP).

What physiological effect does passive propensities at the end-plate cause?

The EPP decays with distance from the end-plate.

What is indicated by the single channel patch clamp recording of ACh receptors?

It's used to measure single ACh receptor currents.

How is the macroscopic endplate current (EPC) produced?

By many ligand-activated ACh receptors.

What does the reversal potential of the macroscopic EPC indicate?

It does not match the E_rev for any single ion.

How does changing ENa or EK affect the EPC reversal potential?

It produces shifts consistent with the ACh receptors being permeable to both Na+ and K+.

What factors contribute to the peak amplitude of the EPC?

Net ion fluxes and postsynaptic membrane potential.

What kind of symptoms does Lambert-Eaton Myasthenic Syndrome (LEMS) present?

Muscle weakness, fatigue, pain, difficulty walking, reduced reflexes.

Which two groups are characterized in patients with LEMS?

Autoimmune disorder and cancer-associated LEMS.

How does Firdapse assist LEMS patients?

It prolongs the opening of remaining Ca2+ channels, increasing ACh release.

What is the role of synaptotagmin in the context of vesicle recycling?

It is involved in the recruitment of clathrin.

What molecular mechanism does dynamin facilitate in the vesicle cycle?

Fission of the vesicle from the membrane.

What can be said about the time scale of synaptic vesicle fusion?

Fusion events occur within milliseconds.

What important element is vital for triggering vesicle fusion?

Calcium ions (Ca2+).

How are synaptic vesicles classified in terms of recycling pools?

Readily releasable pool and reserve pool.

What defines the readily releasable pool of synaptic vesicles?

Vesicles that are immediately available for release upon stimulation.

What happens during exocytosis of synaptic vesicles?

Neurotransmitters are released into the synaptic cleft.

What role do actin filaments play in synaptic vesicle endocytosis?

They are involved in the reformation and movement of vesicles.

What is meant by 'kiss and run' in synaptic vesicle cycling?

A mechanism where vesicles briefly fuse with the membrane and then recycle.

What does 'local recycling' refer to in terms of synaptic vesicles?

Endocytosis of vesicles occurring within presynaptic terminals.

What effect do congenital myasthenic syndromes have on synaptic vesicles?

They result in a loss of synaptic vesicles due to endocytosis defects.

What is one outcome of Clostridial toxins in neuromuscular transmission?

Botulism causes paralysis; tetanus causes muscle spasms.

How do neurons and astrocytes communicate within the tripartite synapse?

Through signaling molecules, primarily neurotransmitters and gliotransmitters.

What enhances the speed of synaptic vesicle endocytosis following neurotransmitter release?

Ultrafast endocytosis mechanisms.

What physiological role do voltage-gated sodium channels have at the neuromuscular junction?

They facilitate action potential propagation in muscle fibers.

What is the distance from the end-plate at which the EPP begins to decay?

The EPP decays with distance from the active zone.