'Synapse showing neurotransmitter vesicles' by David Furness. CC BY-NC
Neurons get a lot of glory for generating the brain’s electrical signals, but a network is only as powerful as the nodes, or synapses, that connect its wires. With each of the brain’s billions of neurons sprouting thousands of branches, synapses like this one number in the trillions.
These neuron-to-neuron junctions help give the brain’s electrical pulses meaning by routing them to where they need to be. When a signal reaches the end of the line (coming from the right, in this picture), the little blue sacs release their contents, neurotransmitters. These chemical couriers float left across the 20-nanometer gap and stick to the surface of the next neuron. They may relay the message by priming the next neuron to fire, or they might stop it short and make it hard for the neuron to activate. Finally, they drift back across the gap, returning to their original post to get ready for the next message.
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