- 1. Relating to isotonicity or isotonia. 2. Having equal tension; denoting solutions possessing the same osmotic pressure; more specifically, limited to solutions in which cells neither swell nor shrink. Thus, a solution that is isosmotic with intracellular fluid will not be i. if it includes solute, such as urea, that freely permeates cell membranes. 3. In physiology, denoting the condition when a contracting muscle shortens against a constant load, as when lifting a weight. Cf.:auxotonic, isometric (2).
* * *iso·ton·ic .ī-sə-'tän-ik adj1) of, relating to, or exhibiting equal osmotic pressure <\isotonic solutions> compare HYPERTONIC (2), HYPOTONIC (2)2) of, relating to, or being muscular contraction in the absence of significant resistance, with marked shortening of muscle fibers, and without great increase in muscle tone compare ISOMETRIC (2)iso·ton·i·cal·ly -i-k(ə-)lē adv
* * *adj.2. describing muscles that have equal tonicity.
* * *iso·ton·ic (i″so-tonґik) [iso- + tonic] 1. denoting a solution in which body cells can be bathed without a net flow of water across the semipermeable cell membrane. 2. denoting a solution having the same tonicity as some other solution with which it is compared, such as physiologic salt solution and the blood serum. 3. maintaining uniform tonus; see under contraction and exercise.
Medical dictionary. 2011.