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channel

 [chan´el]
a passage, cut, or groove through which something can pass or flow across a solid structure.
calcium channel (calcium-sodium channel) a slow voltage-gated channel very permeable to calcium ions and slightly permeable to sodium ions, existing in three subtypes designated L, M, and N and located throughout the body; calcium channels are the main cause of action potentials in certain smooth muscles, and the N channels regulate neurotransmitter release.
fast channel a protein channel, such as a sodium channel, that becomes activated relatively quickly; a fast voltage-gated channel has a much lower activation potential than does the slow type. See also slow channel.
ligand-gated channel a protein channel that opens in response to the binding of a molecule (the ligand) to the protein, which causes a conformational change in the protein molecule. See also voltage-gated channel.
potassium channel a slow voltage-gated channel selective for the passage of potassium ions, found on the surface of a wide variety of cells, including nerve, muscle, and secretory cells; its functions include regulation of cell membrane excitability, regulation of repetitive low frequency firing in some neurons, and recovery of the nerve fiber membrane at the end of the action potential.
protein channel a watery pathway through the interstices of a protein molecule by which ions and small molecules can cross a membrane into or out of a cell by diffusion; protein channels play a vital role in depolarization and repolarization of nerve and muscle fibers, and may have physical characteristics such as shape or diameter that particularly attract certain ions.
slow channel a protein channel such as the calcium channel that is slow to become activated; a slow voltage-gated channel has a much higher activation potential than does the fast type. See also fast channel.
sodium channel a type of fast channel selective for the passage of sodium ions. Voltage-gated sodium channels are the main causes of depolarization and repolarization of nerve membranes during the action potential. In cardiac cells they produce phase 0 of the action potential.
voltage-gated channel a protein channel that can be opened or closed in response to changes in the electric potential across a cell membrane. See also ligand-gated channel.
water channel a channel in a cell membrane that permits passage of water molecules; chemical substances such as vasopressin cause the opening of new channels and increase permeability.

chan·nel

(chan'ĕl),
A furrow, gutter, or groovelike passageway.
See also: canal.
[L. canalis]

channel

(chăn′əl)
n.
1. A furrow, tube, or other groovelike passageway through which something flows.
2. An aqueous pathway through a protein molecule in a cell membrane that modulates the electrical potential across the membrane by controlling the passage of small inorganic ions into and out of the cell.
Drug slang A regional street term for a vein into which a drug is injected
Paranormal See Channeler, Energy channel
Physiology A multiprotein transmembrane complex—ionophore—with an amphipathic pore, which is hydrophobic on either side of the membrane and hydrophilic inside

channel 

A concept relating to the evidence that information about a particular feature of an image is transmitted and processed in the visual pathway approximately independently of information about other domains. The evidence was obtained from various experiments: matching, threshold elevation, after-effect, etc. Examples: the three channels of colour vision theory; the spatial frequency channels. See waterfall after-effect.

chan·nel

(chan'ĕl)
A furrow, gutter, or groovelike passageway.
[L. canalis]
References in periodicals archive ?
The channel section upstream from the T1 turbine has a negligible inflow of cooling water and can be considered a dead zone for the purposes of flow simulation so it was excluded and replaced with a wall to reduce mesh size.
Because the Maillefer, Geyer, and Lacher designs are similar, an unwrapped channel section of the Maillefer design is representative of the melting-section dimensions of the Uniroyal/Geyer and NRM/Lacher designs as well--so the latter two are not analyzed separately.
New machinery has been installed at the West Bromwich factory to speed up the production of the rolled steel channel sections that form the basis of the framing systems and the cable management products.
The range of products will include round and square bars, angle and channel sections, and beams up to the maximum dimension of 300 mm.
Standard 8" and 12" depth channel sections fit through a 24" manhole frame and will accommodate 6" through 12" pipes.
The stream also begins to aggrade, or fill in, with sediment from eroding channel sections upstream.
The mill forms channel sections from 6" to 16" wide and legs from 1" to 4 1/2" deep.
Partitions are constructed of translucent polycarbonate, clipped directly to cold-rolled steel channel sections. Unsurprisingly, the hard surfaces have produced an acoustically reverberant volume, but neither acoustic nor visual privacy were felt to be significant concerns in Ground Zero's design brief.
Called the Two-Way Mixing Screw, its essential features include multiple parallel screw channels, provision of regions of compression and decompression (shallow and deep channel sections), and undercuts on the flight tips to allow forward and backward flow between the parallel channels.
The primary failure mechanism identified was the uplifting and washout of entire channel sections. Much of Albuquerque's drainage system is on slopes of one to five percent and allows velocities in excess of 40 fps.