action (ak´shun)

1. The performance of any of the vital functions, the manner of such performance, or the result of the same. 2. The exertion of any force or power, physical, chemical, or mental. For the actions of some chemical substances, see under the substance. [L. actio, from ago, pp. actus, to do]
ball valve a. intermittent blockage of a tube or outlet of a cavity by some object or material that permits passage in one direction but not in the other.
calorigenic a. increase of heat production of the body, as by the thyroid hormone.thermogenic a;
cumulative a. cumulative effect
salt a. any physicochemical effect produced by hypertonic concentrations of osmotically active electrolytes.
sparing a. the manner in which a nonessential nutritive component, by its presence in the diet, lowers the dietary requirement for an essential component; thus, nonessential l-cysteine spares essential l-methionine and nonessential l-tyrosine spares essential l-phenylalanine.sparing phenomenon;
specific a. the a. of a drug or a method of treatment which has a direct and especially curative effect upon a disease, e.g., the a. of vitamin B12 in pernicious anemia.
specific dynamic a. (SDA) increase of heat production caused by the ingestion of food, especially of protein.
thermogenic a. calorigenic a


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