2. in psychiatry, an unconscious defense mechanism in which unacceptable ideas, fears, and impulses are thrust out or kept out of consciousness. 3. gene r. enzyme repression interference, usually by the endproduct of a pathway, with synthesis of the enzymes of that pathway. gene repression the inhibition of gene transcription of an operon; in prokaryotes repressor binding to the operon is involved.
The ratio of intracellular to extracellular potassium determines neuromuscular and cardiovascular excitability, which is why serum potassium is normally regulated within a narrow range of 3.5 to 5.0 mmol/L. Dietary K+ intake is highly variable, ranging from as low as 40 mmol/day to more than 100 mmol/day.
Extracellular fluids usually have high sodium ion concentrations, and intracellular fluid usually has high potassium ion concentrations. The renal regulation of sodium is closely related to that of potassium because active reabsorption of sodium (under the influence of aldosterone) is accompanied by secretion (and excretion) of potassium.