Calcium channels Flashcards
What are a lot of the enzymes in neurons dependent on?
Ca2+
What is one of the first points of calcium sensitivity?
Recruitment of vesicles away from the reserve pool
What is the trigger for full vesicular fusion?
Ca2+ influx through the channel
Extracellular Ca2+ conc?
1.1mM (milimilar)
Intracellular resting ca2+ conc?
100nm (nanomolar)
What maintains the lower resting intracellular conc of Ca2+ compared to extracellular conc?
Calcium pumps
Which calcium pumps maintain its low intracellular resting conc?
Sodium calcium exchanger, calcium channels (VG calcium channels)
How do calmodulin and calbindin maintain calcium levels?
Physically–> bind to Ca2+
How is it known that calmodulin and calbindin are v important in neuronal functions?
Neurons have a lot more of them than other cell types
Which organelle is a Ca2+ in many cells?
ER
Where is the intracellular Ca2+ released from as a result of IP3 signalling?
ER
Which organelle is v important for calcium buffering in neurons?
Mitochondria
Mitochondrial Ca2+ buffering?
Lot of mitochondrial trafficking into the synapse in response to calcium signalling, and once there they can buffer the Ca2+
How does calcium imaging technology work?
Can use Ca2+ chelators which fluoresce when exposed to UV depending on whether they are bound to Ca2+ or not
What is Ratiometric imaging?
preload cells w/ Ca2+ indicators
excite at 340nm and 380nm, ratio of emission correlates with calcium level
What is Fura-2 (AM)?
calcium chelator, fluoresce when exposed to UV light. (dependent on whether it is bound to calcium or not)
Example of a genetically encoded calcium indicator?
Camelelons
Use of genetically encoded calcium indicators?
In vivo–> mouse model etc
How can the actual Ca2+ conc from the fluorescence imaging?
With two equations
Role of calcium microdomain?
Increases fidelity of neuronal calcium exocytosis coupling to the localised calcium entry
How can sensing machinery be changed w/o having to change themselves?
Can be closer/further away to the calcium channels
Difference in how affected calcium sensing machinery are by buffering?
Further away from Ca2+ channel = more sensitive to buddering
What does the channel and SNARE complex being physically associated together ensure?
V tight coupling between VG channel opening and vesicular transmitter release
Calcium sensing machinery for small molecule transmitter release?
V tightly coupled
Why is the timescale between the Ca2+ entering and the NT being released short?
maintains temporal relationship between AP and signal sent
Homosynaptic plasticity?
Plasticity within a single synapse–> molecular changes within a synapse
Heterosynaptic plasticity?
Input from other synapses can influence NT release
Facilitation of signalling?
Progressive increase in release due to residual calcium at release site during a train of action potentials (short lasting)
Potentiation of signalling?
Increase following repetitive (tetanic) stimulation. Termed PTP, long lasting, involves mitochondrial calcium buffering and release
Depression of signalling?
Progressive decrease in release during a train of action potentials due to decline in readily releasable vesicle pool
