| M channels | Voltage sensitive K channels inactivated by acetylcholine. ACh acting at muscarinic AChR's produces an internal messenger that turns off this class of K channel. A mechanism for regulating the sensitivity of cells to synaptic input. (18 Nov 1997) |
|---|---|
| chloride channels | Cell membrane glycoproteins selective for chloride ions. (12 Dec 1998) |
| potassium channels | Cell membrane glycoproteins selective for potassium ions. (12 Dec 1998) |
| sodium channels | Cell membrane glycoproteins selective for sodium ions. Fast sodium current is associated with the action potential in neural membranes. (12 Dec 1998) |
| ion channels | Gated, ion-selective glycoproteins that traverse membranes. The stimulus for channel gating can be a membrane potential, drug, transmitter, cytoplasmic messenger, or a mechanical deformation. Ion channels which are integral parts of ionotropic neurotransmitter receptors are not included. (12 Dec 1998) |
| cation | <chemistry> A positively-charged ion. (16 Mar 1998) |
| cation-anion difference | <biochemistry> The difference between the sum of the measured cations and anions in the plasma or serum calculated as follows: (Na + K) -(Cl + HCO3) = < 20 mmol/l. Elevated values may occur in diabetic or lactic acidosis; normal or low values occur in bicarbonate-losing metabolic acidoses. Synonym: cation-anion difference. (05 Mar 2000) |
| cation exchange | The process by which a cation in a liquid phase exchanges with another cation present as the counter-ion of a negatively charged solid polymer (cation exchanger). A cation-exchange reaction in removal of the Na+ of a sodium chloride solution is RSO3-H+ + Na+ → RSO3-Na+ + H+ (R is the polymer, RSO3- is the cation exchanger); if this is combined with the anion-exchange reaction, NaCl is removed from the solution (desalting). Cation exchange may also be used chromatographically, to separate cations, and medicinally, to remove a cation; e.g., H+, from gastric contents, or Na+ and K+ in the intestine. See: anion exchange. (05 Mar 2000) |
| cation exchanger | An insoluble solid (usually a polystyrene or a polysaccharide) that has negatively charged radicals attached to it (e.g., -COO-, -SO3-), which can attract and hold cations that pass by in a moving solution if these are more attracted to the acid groups than the counter ion present. (05 Mar 2000) |
| cation-exchange resin | See: cation exchange, cation exchanger. (05 Mar 2000) |
| cation exchange resins | High molecular weight insoluble polymers which contain functional cationic groups that are capable of undergoing exchange reactions; used in various types of chromatography; also to treat hyperkalaemia. (12 Dec 1998) |
| cation exhange resin | <chemistry> An insoluble resin with fixed anionic groups which is used in chromatography to separate cationic molecules. (16 Mar 1998) |