junction /junc·tion/ (-shun) the place of meeting or coming together.junc´tional
gap junction,
junction [jungk´shun]
gap junction,
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.
| 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. |
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.
junction [jungk´shun]
a place of meeting or coming together. adj., adj junc´tional.
atrioventricular junction in the conduction system of the heart, the junction between the atrioventricular node and the nonbranching portion of the bundle of His.
cementoenamel junction the line at which the cementum covering the root of a tooth meets the enamel covering the crown.
gap junction a narrowed portion of the intercellular space, containing channels linking adjacent cells and through which can pass ions, most sugars, amino acids, nucleotides, vitamins, hormones, and cyclic AMP. In electrically excitable tissues the gap junctions serve to transmit electrical impulses via ionic currents and are known as electrotonic synapses; they are present in such tissues as myocardial tissue.
myoneural junction (neuromuscular junction) the site of junction of a motor nerve fiber and a skeletal muscle fiber that it innervates. The discoid expansion of the terminal branch of the axon forms the motor end plate, the neurotransmitter that diffuses across the synapse is acetylcholine.
sclerocorneal junction limbus (def. 2).
ureteropelvic junction the area where the renal pelvis meets the ureter.
gap junction,
n channel between two cells through which communication with neighboring cells occurs.
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.
Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content.
| ?Page tools | ||
|---|---|---|
|