figure 3.22 Mind the gap To communicate with one another, neurons must send messages across a small gap known as a synapse. The diagram on the right shows the axon terminal of a sending neuron, the dendrite of a receiving neuron, and the synapse. On the left is an electron microscope image of actual sending and receiving neurons. The red arrow indicates a location at which one of the sending neuron’s synaptic vesicles is reaching the end of the axon terminal, where it can release neurotransmitters into the synapse.