Synapse is a region where communication occurs between two neurons or a neuron and its effector cell. The neuron that carries the impulse toward the synapse is the presynaptic cell, and the cell receiving the impulse is the postsynaptic cell. Synapses are of two types — chemical and electrical. At a chemical synapse, information passes from the pre- to the postsynaptic neuron through chemical messengers called neurotransmitters. These are released into the synaptic cleft — a fluid-filled space between the cells, then diffuse and bind to the receptor on the postsynaptic cell. This allows the unidirectional relay of the impulse between the cells. Chemical synapses predominate the brain and neuromuscular junction. Compared to the chemical synapse, in an electrical synapse, the pre- and postsynaptic cells are physically connected by gap junctions. As ions passively flow through these junctions, action potential spreads from one cell to another, conducting the impulse. Because electrical synapses are faster and allow synchronized impulse transmission through a large number of cells, they are seen in the cardiac muscles and intestinal smooth muscles.