the length of the axon of the presynaptic neuron change the permeability of the bouton membrane allowing ions to diffuse into the bouton from the surrounding fluid. The presence of causes the synaptic vesicles to fuse with the presynaptic membrane and rupture releasing the transmitter chemical into the cleft. The transmitter chemical, such as acetylcholine , binds weakly with the postsynaptic membrane. This action alters the potential of the membrane and gives rise to a new impulse in the postsynaptic neuron. The transmitter is quickly destroyed by an enzyme (acetylcholine is destroyed by cholinesterase ), otherwise stimulation of the postsynaptic cell would continue unabated and an organism's control over its actions would be lost.
