| coupling phase | The physical relationship of two syntenic genes. If they are on the same chromosome, they are said to be "in coupling" or "in the cis phase"; if on opposite members of a chromosome pair, "in repulsion" or "in the trans phase." (05 Mar 2000) |
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| signal response coupling | The cascade of processes by which an extracellular signal (typically a hormone or neurotransmitter) interacts with a receptor at the cell surface, causing a change in the level of a second messenger for example calcium or cyclic AMP) and ultimately effects a change in the cells functioning (for example: triggering glucose uptake or initiating cell division). Can also be applied to sensory signal transduction, for example of light at photoreceptors. (18 Nov 1997) |
| stimulus secretion coupling | A term used to describe the events that link receipt of a stimulus with the release of materials from membrane bounded vesicles (the analogy is with excitation contraction coupling in the control of muscle contraction). A classical example is the link between membrane depolarisation at the presynaptic terminal and the release of neurotransmitter into the synaptic cleft. (18 Nov 1997) |
| ionic coupling | <chemistry> The same as electrical coupling. (18 Nov 1997) |
| electrical coupling | <physiology> General term for an intimate cytoplasmic contact, mediated by gap junctions, between touching cells, such that electrical current injected into either cell changes the membrane potential of both. In neurons, arrays of gap junctions form electrical synapses, that allow action potentials to pass directly between cells. However, electrical coupling is not confined to excitable cells: many embryonic and adult epithelia are coupled, possibly to allow metabolic cooperation. (18 Nov 1997) |
| electromagnetic coupling | <physics> A means of extracting energy from a magnetically confined plasma, where the plasma expands and pushes on the confining magnetic field, causing electrical energy to be generated in the external field-generating circuits. (09 Oct 1997) |
| energy coupling | <chemistry> The tranfer of energy produced in one reaction to another. (09 Oct 1997) |
| excitation contraction coupling | <physiology> Name given to the chain of processes coupling excitation of a muscle by the arrival of a nervous impulse at the motor end plate to the contraction of the filaments of the sarcomere. The crucial link is the release of calcium from the sarcoplasmic reticulum and the analogy is often drawn between this and stimulus secretion coupling, that also involves calcium release into the cytoplasm. (18 Nov 1997) |
| fixed coupling | Where several premature beats are seen, the interval between each of them and the preceding normal beat is constant. Synonym: constant coupling. Variable coupling, where several extrasystoles are seen, the interval between each of them and the preceding sinus beat varies. (05 Mar 2000) |