Chemical Signaling

Neurons send signals to each other across the synapses. Initially, signals enter into the
cell body of a neuron through their dendrites, and they pass down the axon until their
arrival at the axon terminals. From there, the signal is sent across to the next neuron.
Starting from the time the signal passes along the dendrites and axon, eventually reaching
the axon terminal, it consists of moving electrically charges ions, but at a synapse while
making that transition, it relies more on the structural shape of the chemical
neurotransmitters.

Every two neurons are separated by a gap, called synaptic cleft, at their synaptic site. The
neuron preceding the synapse is known as pre-synaptic neuron and the one following the
synapse is known as post-synaptic neuron. When the action potential of the pre-synaptic
neuron is passed along its axon and reaches the other end of it, it causes synaptic vesicles
to fuse or merge with the membrane. This releases the neurotransmitter molecules to pass
or diffuse across the synaptic cleft to the post-synaptic membrane and slot into receptor
sites.

Neurotransmitter molecules slot into the same-shaped receptor sites in the postsynaptic
membrane. A particular neurotransmitter can either excite a receiving nerve cell and
continue a nerve impulse, or inhibit it. Which of these occurs depends on the type of
membrane channel on the receiving cell.