| premature contraction | A premature contraction of the heart that is independent of the normal rhythm and arises in response to an impulse in some part of the heart other than the sinoatrial node. Synonym: premature beat. (18 Nov 1997) |
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| premature contraction of the heart | When a single heartbeat occurs earlier than normal. This phenomenon can be within normal limits or represent a medically significant arrhythmia. (12 Dec 1998) |
| premature ventricular contraction | <cardiology> A cardiac arrhythmia which originates from within the ventricles. Isolated ventricular contractions are referred to as premature ventricular contractions. Frequent premature ventricular contractions can be potentially unstable and can degrade to a more serious rhythm or cardiac arrest. Acronym: PVC (31 Dec 1997) |
| hourglass contraction | Constriction of the middle portion of a hollow organ, such as the stomach or the gravid uterus. (05 Mar 2000) |
| idiomuscular contraction | A localised contraction of a degenerating muscle, occurring at the point of a sharp blow, independent of the nerve supply. Synonym: idiomuscular contraction, mounding, myoidema. Origin: myo-+ G. Oidema, swelling (05 Mar 2000) |
| isometric contraction | Muscular contractions characterised by increase in tension without change in length. (12 Dec 1998) |
| isometric contraction period | The time between closure of the atrioventricular valves and opening of the semilunar valves. (05 Mar 2000) |
| isotonic contraction | Contraction of a muscle, the tension remaining constant. Since the contractile force is proportional to the overlap of the filaments and the overlap is varying, the numbers of active cross bridges must be changing. (18 Nov 1997) |
| opening contraction | A contraction produced at the time of opening the circuit when using direct current to stimulate the muscle or a motor nerve. (05 Mar 2000) |
| ectoplasmic tube contraction | <cell biology> Model for amoeboid movement in which it is proposed that protrusion of a pseudopod is brought about by contraction of the sub plasmalemmal region everywhere else in the cell thus squeesing the central cytoplasm forwards. See: frontal zone contraction theory. (18 Nov 1997) |
| tonic contraction | Sustained contraction of a muscle, as employed in the maintenance of posture. (05 Mar 2000) |
| escape contraction | Escaped beat, an automatic beat, usually arising from the A-V junction or ventricle, occurring after the next expected normal beat has defaulted; it is therefore always a late beat, terminating a longer cycle than the normal. Synonym: escape contraction. (05 Mar 2000) |
| escape ventricular contraction | An escape beat arising in the ventricle. (05 Mar 2000) |
| 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) |
| uterine contraction | Contraction of the uterine muscle. (12 Dec 1998) |