Also found in: Dictionary, Thesaurus, Legal, Acronyms, Encyclopedia, Wikipedia.
excitation-contraction couplingthe link between excitation of muscle membrane and initiation of force generation at cross-bridges, producing muscle contraction. In all types of muscle this involves a rise in cytoplasmic calcium concentration [Ca2+] but mechanisms for this rise differ substantially. In healthy skeletal muscle the sarcoplasmic reticulum (SR) is the sole effective source of Ca2+ which (within normal physiological function) can only be released from the SR by a muscle action potential (AP), triggered via the motor nerve. In cardiac muscle, the AP is spontaneously initiated in cardiac pacemaker cells rather than by nerves, and Ca2+ release from the SR is triggered by Ca2+ itself, entering the cell from the extracellular fluid during the AP. In certain smooth muscle masses, neural control mechanisms analogous to those of skeletal muscle operate but more commonly, hormones and/or other chemicals are involved; the Ca2+ comes from both the SR and the extracellular fluid, as it does in cardiac muscle, but mediated largely by different mechanisms.
an act of irritation or stimulation; a condition of being excited or of responding to a stimulus; the addition of energy, as the excitation of a molecule by absorption of photons.
in the stimulation of muscle contraction this is the coupling which occurs at the sarcolemma-sarcoplasmic reticulum junction. Mediated by the release of calcium ions in the aqueous sarcoplasm.
conversion of an excitation stimulus into contraction of the effector muscle fiber; ionic calcium is the link between the two.
electrostimulation of a muscle by placing the electrode on its nerve.
in the stimulation of muscular contraction this is the stimulation of secretion of acetylcholine from the vesicles in the cholinergic nerve terminals into the synaptic cleft at the nerve-muscle junction.
see irritation nervous signs.