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.
Effects of changing K+ concentration. altering either the intracellular or extracellular K+ concentration has substantial effects on the resting membrane potential, and therefore on the ability of neurons and muscle cells to reach action potential threshold. HYPERKALEMIA = elevated plasma (extracellular fluid) K+ concentration caused by: increased intake. decreased renal elimination renal failure. adrenal disease (alters function of hormones that regulate kidney function) medications that alter kidney function angiotensin converting enzyme (ACE) inhibitors.