gap junction

junction /junc·tion/ (-shun) the place of meeting or coming together.junc´tional

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adherent junction  a type of intercellular junction that links cell membranes and cytoskeletal elements within and between cells, connecting adjacent cells mechanically.

amelodentinal junction  dentinoenamel j.

atrioventricular junction , AV junction part or all of the region comprising the atrioventricular node and the bundle of His, with the bundle branches sometimes specifically excluded.

cementoenamel junction  the line at which the cementum covering the root of a tooth and the enamel covering its crown meet, designated anatomically as the cervical line.

dentinocemental junction  the line of meeting of the dentin and cementum on the root of a tooth.

dentinoenamel junction  the plane of meeting between dentin and enamel on the crown of a tooth.

esophagogastric junction  the site of transition from the stratified squamous epithelium of the esophagus to the simple columnar epithelium of the cardia of the stomach.

gap junction  a narrowed portion of the intercellular space containing channels linking adjacent cells and through which pass ions, most sugars, amino acids, nucleotides, vitamins, hormones, and cyclic AMP. In electrically excitable tissues, these gap junctions transmit electrical impulses via ionic currents and are known as electrotonic synapses.

Gap junctions providing passageways between the interiors of adjacent cells.

gastroesophageal junction  esophagogastric j.

ileocecal junction  the junction of the ileum and cecum, located at the lower right side of the abdomen and fixed to the posterior abdominal wall.

intercellular junctions  specialized regions on the borders of cells that provide connections between adjacent cells.

mucocutaneous junction  the site of transition between skin and mucous membrane.

mucogingival junction  the histologically distinct line marking the separation of the gingival tissue from the oral mucosa.

myoneural junction , neuromuscular junction the site of apposition between a nerve fiber and the motor end plate of the skeletal muscle which it innervates.

occluding junction  tight j.

sclerocorneal junction  corneal limbus.

tight junction  an intercellular junction at which adjacent plasma membranes are joined tightly together by interlinked rows of integral membrane proteins, limiting or eliminating the intercellular passage of molecules.

ureteropelvic junction  the junction between the ureter and the renal pelvis.

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gap junction

n.

A gap between adjacent cell membranes containing very fine latticelike connections that allow physiologic components to pass directly from cell to cell. Also called nexus.

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gap junction,

a type of junction between cells, consisting of a narrowed portion of the intercellular space that contains channels or pores composed of hexagonal arrays of membrane-spanning proteins around a central lumen (connexon), through which pass ions and small molecules. In electrically excitable tissues such as myocardial tissue and the central nervous system, gap junctions serve to transmit electrical impulses by movement of ions and are known as electrotonic synapses. Also called nexus. See also connexon.

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gap junction,

n channel between two cells through which communication with neighboring cells occurs.

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synapse 

The place where a nerve impulse is transmitted from one neuron to another. This transmission is usually mediated by neurotransmitters (e.g. acetylcholine, noradrenaline (norepinephrine), glutamate, etc.) that are released by the presynaptic neuron, then diffuse across the synaptic cleft (about 20-50 nm wide) to bind to receptor sites on the postsynaptic membrane and generate an electrical change in the postsynaptic neuron, which results in either depolarization (excitation) or hyperpolarization (inhibition). This is often referred to as a chemical synapse. There is another type of synapse called an electrotonic synapse (electrical synapse) in which electrical impulses are transmitted via ionic currents from one neuron to another by direct propagation across a gap junction (2-3nm wide). Electrotonic synapses are rare in vertebrates and have been found at only a few central nervous sites. It is estimated that a cortical neuron, for example, makes some 5000-10 000 synapses with surrounding neurons. See neuron; neurotransmitter; receptor potential.