Neurones are electrically excitable cells, which means that they can transmit electrical nerve impulses.A nerve impulses are electrical charges that travels along the membrane of a neuron. But this electrical current can not pass directly from one to other neuron because between the end of an axon and the next dendrite there is no contact, there is a small gap and same structures known as synapse. Synapses are functional connections between neurons, or between neurons and other types of cellsRemember that a single neuron connects to thousands of other neurons.This is a drawing of a synapse:
We can difference three components
The presynaptic neuron is the transmitting cell, its axon terminal has a lot of vesicles full of neurotransmiters. A neurotransmitter is a chemical message that is used to relay electrical signals between a neuron and another cell
The possinaptic neuron is the receiving cell, It has a lot the neurotransmiter receptor in ist membrane.
The synaptic cleft is the gap between both. (about 20 nm wide)
When a nerve impulse reaches the axon terminal, it causes the neurotransmitter vesicles to fuse with the terminal membrane, and the neurotransmitter is released into the synaptic cleft.When the neurotransmitters diffuse across the synaptic cleft they bind to receptor proteins on the membrane of the postsynaptic cell and causes a nerve impulse to start on the membrane of this neuron.
This video can help to understand the process (action potential is as nerve impulse is transmitted)