Chemical Neuro Communication Flashcards
Synaptic Transmission
NT (chemical signal) transmitted across synapse from presynaptic to postsynaptic neuron
Synaptic Transmission Steps (1-5)
- Action potential arrives at axon terminal, changing membrane potential
- Voltage-gated calcium channels open and Ca2+ ions enter
- Ca2+ entry causes vesicles to fuse with membrane and release transmitter into
synapse - Transmitter binds to postsynaptic receptor in postsynaptic membrane, which
opens ion channel - Ion flow creates EPSP or IPSP in postsynaptic neuron
Otto Loewi’s Key Experiment: what was it and what did it show?
frog heart was in a solution, vagus nerve was stimulated and heart was contracted.
took solution from one heart and transferred to another heart.
result showed there is something in the solution that leads to the same response in heart two; it slowed the heart beat
where does exocytosis occur?
in the active zone
is also where most of the Ca2+ ion channels live
located at the end of axon; is where you will see exocytosis in the vesicle using NT
what does the CA+ ion influx do? what is it a signal for?
changes the membrane potential (just like how Na+ does)
also serve as a signal:
when Ca2+ enters, this is the cue for the vesicles that are hanging out in the nerve terminal to fuse with the membrane and release NT into the synaptic cleft
What specialized proteins mediate calcium ions’ ability to cue vesicles to fuse to membrane?
SNAREs and synaptotagmin (embedded in the membrane) help drive exocytosis, help with membrane fusion, and ultimately transmitter release
Exocytosis: SNAREs
what are they and what types are thera?
proteins that can be thought of as tethers (a flexible attachment that helps secure something that can move)
v-SNARE: on vesicles
t-SNARE: on target membrane
What is SNARE docking?
when t-SNARE and v-SNAREs connect to help tie vesicle to target membrane
when they connect, they are called a trans-SNARE complex
What is a a trans-SNARE complex?
this is what they call it when t-SNARE and v-SNAREs connect to help tie vesicle to target membrane
How do synaptotagmin interact with Ca2+ influx?
Ca2+ ions bind to synaptotagmin.
once calcium is bound to synaptotagmin, the complex of the SNAREs is going to change shape. It becomes a cis-SNARE complex
cis-SNARE complex
the two sides of the membrane are brough together in a zipper-like way (bilayer fusion) to release NT from vesicle (opens membrane to release nt)
synaptotagmin
proteins embedded in the cell membrane that catalyze vesicle fusion and NT release
how does botox function in terms of SNAREs?
botulinum toxin (botox) endocytosis into the cell, breaks up into two pieces and interferes with SNARE proteins (cuts them) so signal is not sent.
chemical communication is disturbed between nerve and muscle fiber
What are the deficits in synaptic transmission in Parkinson’s Disease?
abnormal accumulation and aggregation of alpha synuclein protein (disrupts exocytosis process) in form of Lewy bodies and Lewy neurites
misfolded alpha synuclein protein disrupts exocytosis and disrupts thinking, movement, and behavior
what is the difference between up and down-regulation?
up: increase in number of synapses
down: decrease in num of synapses
changing number of receptors can change strength of signal
