Lecture 11-Pre-Synaptic Mechanisms Flashcards
What is the function of SNARE proteins?
regulate the release of vesicles from the pre-synaptic membrane
How does botox act?
Attacks snare proteins (synaptobrevin or SNAP-25) to inhibit vesicle release and cause muscle relaxation
What enzyme breaks down acetylcholine?
Cholinesterase breaks Ach into choline and acetate
What are 3 methods that are used to clear Ach from the synaptic cleft?
- Diffusion
- Cholinesterase enzyme
- Na coupled transporter
How can we pharmacologically manipulate a failing Ach synapse?
- Mimic NT
- Block Cholinesterase
- Block Na-coupled transporter
What proteins make up gap junctions?
6 connexins
Why are gap junctions not effective in all areas of the nervous system?
- gap is sometime physically too wide
- cell size is mismatched
What are three differences between the activity of a chemical and an electrical synapse?
- Chem is unidirectional whereas electrical can be bidirectional
- Chem is slower due to synaptic delay where as electrical is faster
- Chem is more easily modulated because of many steps involved whereas electrical is harder to control
What is the second messenger that is used to couple membrane depolarization with NT release?
Calcium
Where is calcium more concentrated?
outside the cell
What is Aequorin?
photoprotein that emits light upon binding to calcium
What is an MEPP?
Mini-End Plate Potential- represents the response of a muscle to the release of one vesicle of Ach from the pre-synaptic membrane
What is the function of synapsin?
SNARE protein that tethers the vesicle to cytoskeletal elements to maintain an actively ready pool of vesicles that can be mobilized when neeeded
What is the function of SNARE proteins such as synaptobrevin, syntaxin and SNAP-25?
embedded in membrane and mediate docking of the vesicle to the pre-synaptic membrane
What is the function of SNARE proteins such as synaptotagmin?
Sense the elevation of calcium and form a fusion pore that enlarges and allows for release of NT from vesicle
