Vesicles filled with the neurotransmitter are in the terminal region of the
presynaptic neuron. When the action potential reaches the terminal region
of this neuron, calcium channels open and calcium rushes into the cell from
the surrounding. It is thought that the calcium binds a protein called
synapsin I which is a protein that acts as a bridge between the vesicle and
the cytoskeleton. When calcium binds synapsin I, it releases the vesicle
and the vesicle moves toward the membrane and ultimately binds it. The
contents of the vesicle are dumped into the synaptic cleft. (Please note
that the above mechanism is still experimental and it involves many other
proteins and cellular components that I haven't listed). The
neurotransmitters bind the membrane receptors of the postsynaptic neuron.
These membrane receptors (acetylcholine receptors, for example) are
channels, which open upon binding with the neurotransmitter and allow the
influx and eflux of sodium and potassium. This continues the action
potential in the next neuron.
The type of postsynaptic membrane receptor determines if the
neurotransmitter is excitatory or inhibitory. For example, acetylcholine
can be excitatory if it binds a beta 1 adrenergic receptor. It has
inhibitory effects when it binds beta 2 adrenergic receptors. So the type
of action is mainly due to the type of receptor on the postsynaptic cell.
Good luck
Gary Potikyan
University of California, San Diego
kpotikya at ucsd.edu
--------------------------------------------
Christian Guttmann <x98-cgu at nada.kth.se> wrote in message
news:373F2807.F33AD2C at nada.kth.se...
> The question is how can an action potential, which reaches the
> presynaptic terminal of a chemical synapse, cause a transmittor
> release?
>> My answer would be:
> If this happens, the vesicels in the synapse would get closer to the
> membran, fusionate, release most of there transmitters and
> finally getting back to the intracellular area.
> Right or Wrong?
>> Another question: What is the difference between excitatory and
> inhibatory transmittor(examples)? And what determines if a
> cell has the excitatory or inhibitatory effect?
>> I think the first questions could be that, i.g. Serotonin and glycin are
>> inhibitatory transmittors and petins, like endorphine are excitatory???
> Second questions ????
>> Do you have an answer?
>> --
> Christian Guttmann Mobile Tel. : +46-(0)70 414 99 76
> Professorsslingan 19-119 Email : guttmann at gmx.de> 10405 Stockholm Home Page :
www.student.nada.kth.se/~x98-cgu/
> Sweden
>>>
