Chemical synapses:

1) 30-50 nm distance between pre- and post-synaptic membrane, (adjacent extracellular space: typically 20 nm)
2) cytoplasmic discontinuity
3) ultrastructure: presynaptic active zone, synaptic vesicles, postsynaptic receptors
4) chemical transmitterŅ° ņ««— transmission
5) synaptic delay:at least 0.3 ms, usually 1-5 ms or longer

(presynaptic AP, increased presynaptic Ca2+ permeability, Ca2+ influx, release of neurotransmitter(NT) by exocytosis of vesicles, reaction of transmitter with postsynaptic receptors,
activation of synaptic channels; synaptic currents produces postsynaptic potential, postsynaptic AP)

6) direction of transmission: unidirectional

7) mediate either excitatory or inhibitory actions
8) tend to be involved in behaviors more complex than electrical synapse.
9) are more flexible (plasticity--> higher brain functions)
10) amplification of neuronal signals--> generates large PSP
11) each vesicle contains several thousand molecules of NTs










BRAIN FACTS