6.5: Synaptic Signaling
Neurons communicate with each other and to other cells mainly through chemical signaling at synapses. These specialized regions are where the axon terminal of the presynaptic cell—the neuron sending the message—meets the postsynaptic cell receiving the message.
The signal consists of neurotransmitter molecules, which are stored in the axon terminal within membrane-bound organelles called synaptic vesicles. When an electrical signal known as an action potential occurs in the presynaptic neuron, it triggers these vesicles to fuse to the cell membrane.
When the vesicles fuse, they release their neurotransmitter into the synaptic cleft—the narrow space between cells. The neurotransmitter then diffuses across and binds to its postsynaptic receptors. The binding elicits a response in the postsynaptic cell, which in this case, is a neuron, and an action potential may be produced.
Ultimately, synaptic signaling allows neurons to transmit information to other cells near and far.