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Gap junctions were first described as close appositions as other tight junctions, but following electron microscopy studies in 1967, they were renamed gap junctions to distinguish them from tight junctions. [2] They bridge a 2-4 nm gap between cell membranes. [3] Gap junctions use protein complexes known as connexons to
Each gap junction (sometimes called a nexus) contains numerous gap junction channels that cross the plasma membranes of both cells. [11] With a lumen diameter of about 1.2 to 2.0 nm, [2] [12] the pore of a gap junction channel is wide enough to allow ions and even medium-size molecules like signaling molecules to flow from one cell to the next, [2] [13] thereby connecting the two cells' cytoplasm.
Gap junctions play vital roles in the human body, [11] including their role in the uniform contractile of the heart muscle. [11] They are also relevant in signal transfers in the brain, and their absence shows a decreased cell density in the brain. [12] Retinal and skin cells are also dependent on gap junctions in cell differentiation and ...
Gap junctions are the main site of cell-cell signaling or communication that allow small molecules to diffuse between adjacent cells. In vertebrates, gap junctions are composed of transmembrane proteins called connexins. They form hexagonal pores or channels through which ions, sugars, and other small molecules can pass.
Gap junctions connect the cytoplasms of neighboring cells electrically allowing cardiac action potentials to spread between cardiac cells by permitting the passage of ions between cells, producing depolarization of the heart muscle. [3] [2] All of these junctions work together as a single unit called the area composita. [2]
An electrical synapse is an electrically conductive link between two abutting neurons that is formed at a narrow gap between the pre- and postsynaptic cells, known as a gap junction. At gap junctions, cells approach within about 3.5 nm of each other, rather than the 20 to 40 nm distance that separates cells at chemical synapses.
Connexins are commonly named according to their molecular weights, e.g. Cx26 is the connexin protein of 26 kDa. A competing nomenclature is the gap junction protein system, where connexins are sorted by their α (GJA) and β (GJB) forms, with additional connexins grouped into the C, D and E groupings, followed by an identifying number, e.g. GJA1 corresponds to Cx43.
There are gap junctions among supporting cells and also between supporting cells and hair cells, the gap junctions are made of connexins which are three times denser in the apex than the base. The gap junctions play an important role in regulating the concentration of intracellular K+ between the endolymph and the perilymph , maintaining pH ...