Electrical synapse

An electrical synapse is a synapse in which electrical current flows directly from one cell to another via a gap junction. It is one of the two major classes of synapses, the other being the chemical synapse. At a gap junction, the two neurons are separated by a very narrow gap of about 2–4 nm of each other, a distance much smaller than the 20- to 40-nanometer distance that separates cells at a chemical synapse. Electrical synapses co-exist with chemical synapses in the nervous system of many animals, from nematodes to arthropods to vertebrates, including mammals. Most synapses in the brain are chemical, but electrical synapses are an important minority with a distinct purpose.

Compared to chemical synapses, electrical synapses conduct nerve impulses faster and provide continuous-time bidirectional coupling via linked cytoplasm. As such, the notion of signal directionality across these synapses is not always defined. They are known to produce synchronization of network activity in the brain and can create chaotic network level dynamics. In situations where a signal direction can be defined, they lack gain (unlike chemical synapses)—the signal in the postsynaptic neuron is the same or smaller than that of the originating neuron. The fundamental bases for perceiving electrical synapses comes down to the connexons that are located in the gap junction between two neurons. Electrical synapses are often found in neural systems that require the fastest possible response, such as defensive reflexes. An important characteristic of electrical synapses is that they are mostly bidirectional, allowing impulse transmission in either direction.