| 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) |
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| 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) |
| frontal zone contraction theory | Model proposed to account for the movement of giant amoebae in which cytoplasmic contraction at the front of the leading pseudopod (fountain zone) pulls viscoelastic cytoplasm forward in the centre of the cell and forms a tube of more rigid cytoplasm immediately below the plasma membrane behind the active region. The peripheral contracted cytoplasm relaxes into a weaker gel at the rear and is pulled forward in its turn. Contrasts with the ectoplasmic tube contraction model. (18 Nov 1997) |
| front-tap contraction | Contraction of the calf muscles when the anterior surface of the leg is struck. Synonym: Gowers' contraction. (05 Mar 2000) |
| adrenal mass | <radiology> Metastasis, most common (especially lung, melanoma), primary adenocarcinoma, large at diagnosis (greater than 5 cm), usually functional (increased corticosteroids most likely to be Cushing's), rapid growth, benign adrenal adenoma, with or without functional, nonfunctional occurs in 2-8% of population, diff from metastasis: MRI (metastasis bright on T2), biopsy, follow, pheochromocytoma, neuroblastoma, myelolipoma, cyst / pseudocyst see also: adrenal calcification, haemorrhage (12 Dec 1998) |
| apperceptive mass | The already existing knowledge base in a similar or related area with which the new perceptual material is articulated. (05 Mar 2000) |
| atomic mass | <chemistry, physics> The mass of an atom relative to other atoms. The present-day basis of the scale of atomic weights is carbon, the most common isotope of this element has arbitrarily been assigned an atomic weight of 12. The unit of the scale is 1/12 the weight of the carbon atom or roughly the mass of one proton or one neutron. The atomic weight of any element is approximately equal to the total number of protons and neutrons in is nucleus (16 Dec 1997) |
| atomic mass unit | <chemistry> One-twelfth the mass of a neutral atom of the most abundant isotope of carbon. (16 Dec 1997) |
| bilateral adrenal mass | <radiology> Acute granulomatous disease (e.g., TB), metastases (bilateral in 15%), pheochromocytoma (bilateral in 10%), adrenal hyperplasia (adenoma), spontaneous adrenal haemorrhage (12 Dec 1998) |
| body mass index | One of the anthropometric measures of body mass; it has the highest correlation with skinfold thickness or body density. (12 Dec 1998) |
| breast mass | <oncology, surgery> A breast lump may be benign or cancerous. Examples of breast lumps include: breast abscess, fat necrosis, fibroadenoma, fibrocystic breast disease and breast cancer. A breast biopsy is the best way to determine the aetiology of a breast lump. Remember, 80 to 85% of all biopsies are benign. (27 Sep 1997) |