synapses

rectifying transmission

• one way transmission

non rectifying transmission

two way transmission

electrical synapse

• two neurons connected by specialised proteins creating gap junction

• non rectifying

• fast transmission

• often attenuated

connexons and electrical synapse

• 2 connexons per synapse

• 6 connexins per connexon - 12 connexins per synapse

• pore diameter is 1-2nm

• not flexible

drosophila escape reflex

• relies on innexin (invertebrate form of connexin)

• electrical synapses with motor neurons

• gap junctions

chemical synapses

• very flexible

• more plasticity than motor neurons

• primary method for communication

electrical stimulation of vagus nerve effect

slower heart rate

effect of vagus substance in otto loewi experiment

• vagus substance released by heart with vagus nerve slows down heart without vagus nerve

• acetylcholine neurotransmitter released by vagus nerve influences contraction

active zones of chemical synapses

• creates dark areas on EM morphology

• where neurotransmitter is released

• calcium voltage gated channels are found here

why are there many mitochondria in chemical synapses

• lots of energy required for neurotransmitter release in vesicles

• brain uses up to 30% of energy bc of this

SNARE proteins

• synaptobrevin, snap-25 and syntaxin

where is synaptobrevin found

in the vesciles

wher

purpose of snare proteins

• snare proteins bind to eachother

• draw vesicles close to membrane

• neurotransmitter release into presynaptic cleft

what destroy snare proteins and why

• tetanus toxins to stop them from releasing GABA or glycine

spontaneous release

• no calcium

• still some neurotransmitter being released

• smaller size change in post synaptic membrane

• miniature end plate potential

evoked release

• by action potential

• calcium enters cell

• many vesicles fusing with postsynaptic membrane

• end plate poltential

miniature endplate potential

• many small miniature end plate potentials

• stepwise variation

• due to release of one or few quanta

quantum

amount of neurotransmitter per vesicle

quantal current

EPP current / 1 quantum current

how many quanta per action potential

200

clathrin

• involved in vesicle recycling

• binds to vesicles and forms interactions with other clathrin molecules

• hexagon and pentagon conformations

• drags vesicles away from membrane

constants in vesicle recycling

• vesicle size (Determined by clathrin)

• number of