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Lecture

CSB332H1 Lecture Notes - Electrical Synapse, Chemical Synapse, Neurotransmitter


Department
Cell and Systems Biology
Course Code
CSB332H1
Professor
Melanie Woodin

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CSB332H1S L–4,5; Jan. 18, 2012
Synaptic Transmission (Ch.11, 12)
A: also called gap junctions
Fusion of connexion prots other either
side of membrane, physically clamp
together, allow direct current flow
Very useful for fast response or
synchronized activity (reflexes, ex. fish
or invertebrate tail flips)
B: majority of synapses are chemical
Energetically expensive
More complex
Important for ability to have high order
f’ns, can modify chemical synapse
strength more than the electrical
synapse – allows for plasticity
When act pot reaches presynaptic
terminal/bouton depolarization
invades terminal opens voltage-
gated Ca channels critical Ca
influx
Bouton filled w Ca-sensitive prots
exocytosis of neurotransmitter
vesicles
Neurotransmitters flow across
synaptic cleft, bind to post
synaptic rec to initiate electrical or
chemical change in membrane
On avg vesicles contain a quanta of neurotransmitter
Clustering of vesicles at presynaptic membrane – active zone – undergoing
exo & endocytosis
Presynaptic terminal = bouton/knob; expansion containing active zones
Act pot opens voltage-gated Ca channels flows in, required for vesicle
release
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Coined term synapse
Won nobel prize in 1932 for neuron
work
“Father of neuroscience”
Student of John Heccles (nobel prize
of basis of act pot)
Voltage-gated Ca channels highly
concentrated in presynaptic bouton
Eqm pot for Ca ~ eqm pot for Na
Electrochem grad & conc grad for Ca
similar to that of Na
So act pot opens Ca channels (+)
charge flows in; needed for SNARE
complexes (at vesicles & membrane, allow
fusion w presynaptic membrane) to allow
release once fused
Docked vesicles exocytosis
Electron micrograph of synapse
Vesicles at active zone of
presynaptic terminal, reform
using endocytosis
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