 Dear students, in this module we shall define synapses and discuss their types and discuss one type that is electrical synapses in detail. The synapses are the junctions between exon terminals of one exon and the dendrites of an other exon. The transmission of signals takes place from one neuron to the other through these junctions. There are two types of synapses. One are the electrical synapses and the second type is of chemical synapses. We shall discuss electrical synapses in detail. At the electrical synapses, the plasma membranes of pre and post-synaptic cells are in close opposition. Pre and post-synaptic cells are very close to each other and they are electrically coupled through the gap junction proteins. Dear students, the electric current can flow directly from one cell into the other through the gap junction proteins purely by electrical means without involving any chemical transmitter. It is just like a signal transmission along a single exon involving passive spread of local circuit current that depolarizes and excites the neuron ahead. So the transfer of information through these synapses is much rapid. Dear students, the electrical synapses provide a mean of very rapid transmission without involving any chemical in between. However, it has limited efficacy because the signal that is transferred from one neuron to the other through the gap junction proteins is somewhat attenuated. So a single pre-synaptic action potential that arrives in the post-synaptic potential cannot generate an action potential in the post-synaptic cell. When a weak signal arrives, the post-synaptic cell membrane will not be so depolarized that it will generate action potential in the post-synaptic cell as well as the propagation of action potential. This is why most electrical synapses require more than one action potential to be propagated. This limitation reduces the efficacy of electrical synapses, but in spite of their limited efficacy, they have certain advantages. They are particularly effective in synchronization of electrical activity within a group of cells. They can transmit information across a series of cell-cell junction. They can transmit information across a series of cell-cell junction. For example, myocardium of the heart may be a electrical signal, and the muscle cells of the heart may be a very fast transmission of signals. Dear students, the electrical synapses are relatively rare and most of the signaling between neurons takes place through the chemical synapses. However, electrical transmission has been discovered in many cells of the central nervous system. Moreover, in many receptors, like the retina of the eye, electrical synapses are present. Similarly, many smooth muscles have electrical synapses and cardiac muscle fibers, and many other receptor cells and some exones of peripheral nervous system also contain electrical synapses through which transmission of signals takes place rapidly.