Where are synaptic vesicles found? Name their chemical contents? What is the function of these contents?
Synaptic vesicles are found in the bulbous expansion called synaptic knob, at the nerve terminal. Each synaptic vesicle contains as many as 10,000 molecules of a neurotransmitter substance, that is responsible for transmission of nerve impulse across the synapse. When a wave of depolarisation reaches the presynaptic membrane, the voltage-gated calcium channels concentrated at the synapse open and Ca ions diffuse into the terminal from the surrounding fluid. The Ca++ ions stimulate the synaptic vesicles to move to the terminal membrane, fuse with it and then rupture by exocytosis into the cleft. This neurotransmitter diffuses across the synapse and stimulates the membrane of the next neuron.
