Synapse is the junction between axon of one neuron and dendrite of another neuron. These neurons communicate with the help of chemical mediators called as “neurotransmitters.”
The neuron above the synapse is called as “presynaptic neurone,” and the neurone below the synapse is called as “post synaptic neurone.” The junction between presynaptic and postsynaptic neuron is known as “synaptic cleft.”
The release of many quanta of neurotransmitters from the presynaptic membrane is required to transmit the action potentials from one neuron to the other.
Thus, the blanks can be filled with presynaptic neuron; post synaptic neuron; quanta.