Unformatted text preview: right where the vesicle in middle of terminal fuses with membrane. this synaptic vesicle
completely fuses with and collapse into membrane. as more and more vesicle collapse their
membrane into synaptic membrane, this vesicle membrane push off the side. At some place
away from release site, the vesicle membrane is retrieve but stay intact and reform back into
synaptic vesicles and refill
4. newly discover mechanism (occur at synapse) where vesicle keep very close to presynaptic
terminal, where it fuse with membrane and do not completely collapse. instead it form a
fusion-pore, and allow neurotransmitter to rapidly diffuse out. At either 3 or 4 neurotransmitter,
as soon as vesicle collapse or pore is form, diffuse out to extracellular solution because there's
such a high concentration inside cell.
kiss and run mechanism: the vesicle never lose this integrity. once it's empty, it pulls away
from terminal, is recycle and refilled.
step 4 is diffusion of transmitter across narrow space between pre and post synaptic
membrane, called synaptic cleft (see next slide) vesicle collapse
and retrieval fusion-pore kiss and run Steps in Chemical Synaptic Transmission
here at step 4: this is the rapid diffusion of neurotransmitter through narrow synaptic cleft (very
10th of nm, very short distance).
on post-synaptic membrane, there are receptors shown in pink for neurotransmitter.there are 2
types of receptor:
1. if the neurotransmitter bind to receptor and there's a change in ion channel (the receptor is a ion
channel or it's couple with an ion channel). this receptor is ionotropic receptor. the effect can be
opening or closing in ion channel and the resulting changes in ionic fluxes across the membrane
and depolarization or hyperpolarization of postsynaptic cell
2. if the neurotransmitter bind to receptor and trigger metabolic changes,, through second
messenger system. metabotropic. hormone can exert on cell through neurotransmitter when they
bind to metabotropic receptors. Presynaptic
Terminal 3 2 t...
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- Spring '09
- Synaptic Transmission, chemical synaptic transmission