electrotonic synapse


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synapse

 [sin´aps]
the junction between the processes of two neurons or between a neuron and an effector organ, where neural impulses are transmitted by chemical means. The impulse causes the release of a neurotransmitter (e.g., acetylcholine or norepinephrine) from the presynaptic membrane of the axon terminal. The neurotransmitter molecules diffuse across the synaptic cleft, bind with specific receptors on the postsynaptic membrane, causing depolarization or hyperpolarization of the postsynaptic cell. See also neuron.
Components of a synapse. From Applegate, 2000.
axoaxonic synapse one between the axon of one neuron and the axon of another neuron.
axodendritic synapse one between the axon of one neuron and the dendrites of another.
axodendrosomatic synapse one between the axon of one neuron and the dendrites and body of another.
axosomatic synapse one between the axon of one neuron and the body of another.
dendrodendritic synapse one from a dendrite of one cell to a dendrite of another.
electrotonic synapse a special type of gap junction found in tissue such as the myocardium.

gap junc·tion

1. an intercellular junction formerly considered to be a tight, membrane-to-membrane junction (macula occludens) but now shown to have a 2-nm gap between apposed cell membranes; the gap is not void but contains subunits in the form of polygonal lattices, which are the intercellular aspects of the two connexons that fit together, forming a channel between the cytoplasms of the two cells; it occurs in epithelia, between certain nerve cells, and in smooth and cardiac muscle; it is believed to mediate electrotonic coupling, which allows ionic currents to pass from one cell to another.
See also: synapse.
See also: connexons.
2. areas of increased electrochemical communication between myometrial cells that aid in the propagation of the contractions of labor.
See also: connexons.

electrotonic synapse

a gap junction that transmits electrical impulses in electrically excitable tissue. See also gap junction.